Anreicherung,verteilung, umwandlung und ausscheidung von DDT-14C bei Solea solea (Pisces: Soleidae)

Common soles Solea solea (L.) are extremely suitable for studying the fate of pesticides in marine fish by means of laboratory experiments involving small-sized, accurately controlled, closed aquarium systems. In 5 different experiments, a total of 16 fishes of Age Group I were maintained in water of 10°C and 20‰ S continuously filtered through charcoal, and given oral doses of 0.85 μg DDT-¹⁴C up to 5 times/week. A total application of 1.7, 17 or 35 μg DDT-¹⁴C, corresponding to 3, 28, or 57 experimental days, resulted in 72, 60 or 43% DDT-¹⁴C accumulation. After feeding with 17 μg unlabelled DDT over a period of 4 weeks and final feeding with 1.7 μg ¹⁴C-labelled DDT for 2 days, S. solea displayed the same percentage (74%) of accumulated DDT-¹⁴C as after feeding with 1.7 μg DDT-¹⁴C without prior feeding. Therefore, the decreasing accumulation percentages with inereasing doses, i.e., with longer application periods, are due to elimination during the application period. During a period of 2 months in pesticide-free water, S. solea eliminated 62% of the DDT-¹⁴C which it had accumulated after feeding with 17 μg DDT-¹⁴C over a period of 4 weeks. The gastro-intestinal tract is assumed to be a major route of DDT elimination. Independent of dosage, there was a characteristic distribution pattern of accumulated DDT: brain, liver and gastro-intestinal tract ranked highest, while the concentration in skeletal muscle was lowest. Even during the elimination period the pattern appeared unchanged. DDE, DDD and a polar component occurred as metabolites, but in all organs more than 80% of the accumulated DDT remained unchanged. Percentages of metabolites were higher in liver and gastro-intestinal tract than in skeletal muscle. Prolonged exposure to DDT in the diet induced DDT transformation in the gastro-intestinal contents, most probably in the bacterial flora of the gut.     

Pharmacokinetics of [14C]-atrazine in rhesus monkeys,single-dose intravenous and oral administration

This is the first study regarding the pharmacokinetics of [¹⁴C]-atrazine conducted with rhesus monkeys. The animals received one dose (0.25 mg) intravenously (IV) or three doses (1, 10, or 100 mg) orally. Plasma, urine, and feces were collected at defined times up to 7 days post-dosing. Sample radioactivity was measured to determine the mass equivalent. IV administered [¹⁴C]-atrazine disappeared rapidly from blood, with an elimination half-life of about 5.5 ± 1.1 h. The pharmacokinetic profiles of [¹⁴C]-atrazine following oral administration at the three dose levels show that kinetic parameters such as AUC and C _max are linearly correlated with the dose. Seven days after dosing, urinary and fecal excretion of [¹⁴C]-atrazine reached 99% of total administered dose in the IV group and 91–95% in the three oral dose groups. In the IV-administered monkeys, approximately 85% of the dose was excreted in urine and 12% in feces. In three oral dose groups, urinary and fecal radioactivity recoveries approximated 57% and 21%, 58% and 25%, and 53% and 35%, respectively. More than 50% of the total urinary excreted radioactivity was found within the first 24 h after dosing. In conclusion, the principal elimination of [¹⁴C]-atrazine, IV and orally administered, is via urine. The oral bioavailability was 60% or higher. There was a significant linear correlation between administered oral dose and plasma concentration. Overall oral dose accountability ranged from 91% to 95%. Data generated may be useful in the risk assessment of human exposure to environmental atrazine contamination.     

Biodegradation of aromatic hydrocarbon in marine sediments of three North Sea oil fields

On a survey around three North Sea oil fields in 1980 the biodegradation of the hydrocarbons ¹⁴C-naphthalene and ¹⁴C-benzo[a]pyrene was measured. An amino acid mixture was taken as reference substrate for total heterotrophic activity. The rate of uptake of naphthalene was found to increase with decreasing distance from the oil platform at all fields with maximum values at stations 0.5 miles (ca 0.8 km) from the centre of oil activity. Data on naphthalene uptake parallel GC-MS data for aromatic hydrocarbons and allow an estimation of the actual uptake velocity of naphthalene in the sediment to be made. A significant mineralisation of benzo[a]pyrene could only occasionally be detected. The respiration of amino acids did not show any pattern related to the oil field activities.     

Uptake and accumulation of naphthalene by the oyster Ostrea edulis,in a flow-through system

A flow-through system was used to follow naphthalene and naphthalene metabolite accumulation in the seawater and in the tissue of the oyster Ostrea edulis. After 72 h, 82.5% of the naphthalene carbon was recovered from the system. Glucose was added to seawater to stimulate the pathways of glucose metabolism in the oysters. Streptomycin (100 ppm) reduced microbial oxidation of naphthalene and glucose, and reduced bacterial growth. However, even in the presence of streptomycin, microbial oxidation of naphthalene was considerable. The main oxidation product recovered from seawater was ¹⁴CO₂. Radioactivity was also associated with compounds which separated by TLC with 2- and 1- naphthol. The pattern of naphthalene uptake and accumulation in oyster tissues was relatively constant after only a few hours of exposure to naphthalene. The potential of tissues to accumulate naphthalene was shown to be a function of multiple variables such as nutritional state, lipid concentration, length of exposure to naphthalene, and the external naphthalene concentration. Carbon-14-labeled metabolites derived from ¹⁴C-naphthalene were consistently recovered from digests of the oyster tissues. Non-CO₂ alkaline-soluble substances were the primary metabolites. Hexane-extractable substances, which separated by TLC with known standards of 2- and 1- naphthol, were consistently recovered from seawater and tissue digests. It was not possible to conclude that these metabolites were a result of naphthalene metabolism by oyster enzyme systems.     

Effect of copper on ion- and osmoregulation in the shore crab Carcinus maenas

The uptake and effect of dissolved copper on regulation of hemolymph osmolality and Na⁺, K⁺, Cl^-, Ca⁺⁺, and Mg⁺⁺ concentrations in the shore crab Carcinus maenas (L.) were determined at 400 mOsm (=14 S) ambient salinity. One mg Cu l^-1 resulted in 50% mortality in 11 to 22 d; the highest sensitivity was observed around the moulting period. 0.25 and 0.5 mg Cu l^-1 were not lethal after a onemonth exposure. Ten, 1, and 0.5 mg Cu l^-1 altered regulation of osmolality, Na⁺, K⁺, and Cl^- concentrations, while 0.25 mg Cu l^-1 did not. Exposure to 1 mg Cu l^-1 reduced hemolymph osmolality and Na⁺, K⁺, and Cl^- concentrations to 80 to 90% of controls within 4 to 6 d and no further reduction was observed during a 21-d exposure. The effect of various copper concentrations on these four parameters were almost identical and the highest sensitivity was observed around the moulting period. Hemolymph calcium levels increased 20 to 80% in crabs exposed to 1 mg Cu l^-1, while they decreased 20 to 30% in crabs exposed to 0.5 mg Cu l^-1. Prolonged exposure to copper caused 20 to 70% reductions in hemolymph magnesium levels. Crabs exposed to 0.5 mg Cu l^-1 for 29 d accumulated copper in hepatopancreas, gills, carapace, heart, testes, and hypodermis, but not in muscles and hemolymph. Increased copper levels in crabs exposed to 0.25 mg Cu l^-1 were observed in hepatopancreas, gills, and carapace only. The present results suggest that effects of copper on ion regulatory processes in part explain why the toxicity of copper towards euryhaline invertebrates increases at low salinities.     

Studies on the mechanism of biosynthesis of wax esters in Euchaeta norvegica

Preparations of Euchaeta norvegica catalyse the incorporation of (1-¹⁴C) hexadecanol, (9,10-³H₂) oleic acid, (U-¹⁴C) glucose, (U-¹⁴C) alanine and (U-¹⁴C) aspartic acid into wax esters. Both the fatty alcohol and fatty acid moieties of the wax esters are labelled, indicating de novo biosynthesis. A limited interconversion of fatty acid and fatty alcohol has been demonstrated. Incorporation of glucose into wax esters is diminished by prior starving of E. norvegica; it is also reduced in the presence of ecdysterone. Formation of wax esters from glucose is inhibited by increased oxygen tensions, rotenone and dinitrophenol, and is relatively insensitive to decreased oxygen tensions and cyanide. The data are discussed with particular reference to the reasons why wax esters are biosynthesised by calanoids.     

Transport of naphthalene in the oyster Ostrea edulis

In small oysters (Ostrea edulis), transport of naphthalene between tissues is primarily by diffusion and not via the circulatory system. In intact oysters, accumulation in the adductor muscle and body followed accumulation in the gills after a large lag-time. In isolated tissues with no shell to impede water flux over the body and adductor muscle, there was no lag-time. The molecular diffusivity (D) of naphthalene in oyster tissue, estimated by Fick's second law of diffusion is D=8x10^-8 cm² s^-1, a value similar to D determined for lateral diffusion of lipophilic compounds in lipid membrane systems.     

Influence of simulated tidal cycles on aromatic hydrocarbon uptake and elimination by the shore crab Hemigrapsus nudus

Specimens of the intertidal crab Hemigrapsus nudus (Dana, 1851) were collected near Sitka, Alaska, in 1983, and were used in laboratory experiments to determine the influence of periodic exposure to air on the toxicity, uptake, and elimination of two aromatic hydrocarbons, toluene and naphthalene. Three tidal cycles were simulated; i.e., crabs spent 0, 33, or 66% of the time in air and the remainder of the time in toxicant or seawater solutions. Naphthalene was 10 to 20 times more toxic than toluene: naphthalene caused locomotory impairment or killed the crabs more rapidly and at concentrations lower than those of toluene. In tissues, naphthalene was accumulated faster and to higher concentrations than was toluene. Exposure to air 66% of the time reduced mortality as well as the rate at which toluene and naphthalene were accumulated and lost. Crabs exposed to air had significantly higher respiration rates than those submerged in seawater; thus, reduced rates of accumulation and loss of hydrocarbons were not caused by general metabolic quiescence. Exposure to air reduced the time the crabs were in contact with water-borne hydrocarbons and, therefore, reduced toxicity of the hydrocarbons. Once crabs had accumulated the toxicants, however, elimination was hindered by exposure to air, even for the somewhat volatile compound toluene.     

The effect of cadmium on antioxidant responses and the susceptibility to oxidative stress in the hydrothermal vent mussel Bathymodiolus azoricus

Hydrothermal vents are a unique environment of extreme physical–chemical characteristics and biological species composition. Cd is a toxic non-essential metal present in high concentrations in the hydrothermal vent environment, contrary to those found in marine coastal areas. Cd toxicity has been related, among other things, with reactive oxygen species production, even though this is a non-redox metal. Bathymodiolus azoricus is a deep-sea Mytilid bivalve very common in the Mid Atlantic Ridge (MAR) hydrothermal vent fields and very little is known about the antioxidant defence system in this specie. Because lethal Cd concentration in B. azoricus is unknown, the aim of this study was to assess the effects of a Cd concentration higher than that found in the hydrothermal vents on oxidative stress biomarkers, such as antioxidant enzymes. Mussels were exposed to 100 μg l⁻¹ Cd during 24, 48 and 144 h, respectively, in a pressurized aquarium (IPOCAMP). Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), total oxyradical scavenging capacity (TOSC), metallothionein (MT) and lipid peroxidation (LPO) were measured in the gills and mantle of B. azoricus. The results indicate that gills are first affected by Cd toxicity. This may be due to different physiological functions of the tissues and by the presence of thio and methanotrophic symbiotic bacteria in the gills. The SOD and CAT are inhibited during the first day of exposure in the gills, although TOSC and MT concentrations were the same in control and exposed mussels. In the mantle, enzymatic activation only occurred after 6 days, and no significant differences in MT concentrations were found in the control and exposed mussels during the first day, as observed in the gills.     

Metabolism of palmitic,linoleic, and linolenic acids in adult oysters,Crassostrea virginica

This study investigated incorporation and metabolism of saturated [(1-¹⁴C) 16:0] and unsaturated [(1-¹⁴C) 18:26 and (1-¹⁴C) 18:33] fatty acids in adult eastern oysters,Crassostrea virginica Gmelin (spawned from parents obtained in 1986 from Mobjack Bay, Virginia, USA), and the influence of temperature on these processes. InC. virginica, incorporation of injected palmitic (16:0) and linolenic (18:33) acids was increased when oysters which had been grown in warm water (22 to 23°C) were transfered to cold water (5 to 7°C) for 8 to 18 d. Incorporation of linoleic acid (18:26) was unchanged under these conditions. The changes in concentration may have been linked to depression of metabolism in these oysters, in particular that of 16:0, which was reduced by 90%. Oxidation of incorporated fatty acids was much higher in warm than in cold water. Cold-temperature conditioning ofC. virginica altered the distribution of fatty acids among the neutral and polar lipid fractions. Long-term exposure to cold water increased the proportion of fatty acids in the polar fraction, which may be related to maintenance of membrane fluidity. Short-term exposure to cold water had the opposite effect, which may be due to increased energy requirements as the oyster adapts to new conditions. Reutilization of¹⁴C-acyl groups demonstrated de novo synthesis of 16:0 and 18:0 fatty acids. Only limited elongation and no desaturation of the administered fatty acids was observed.     

Uptake and elimination kinetics of triphenyltin hydroxide by two fish species

The uptake from water and the elimination of carbon‐14 radiolabelled triphenyltin hydroxide ([¹⁴C]TPTH) was studied in two fish species: guppy (Poecilia reticulata) and rainbow trout larvae (Salmo gairdneri). During all the experiments no steady state in fish was found. TPTH was rapidly taken up, while elimination was very slow. Uptake and elimination rate constants (k ₁ and k ₂, respectively), and a bioconcentration factor were estimated, assuming first order kinetics.

During eight days of exposure of guppy to TPTH an uptake rate constant k ₁ of 70±7L/kg.d and an elimination rate constant k ₂ of 0.005 ±0.029d ^‐1 was found. This resulted in a biconcentration factor of at least 2.1 × 10³L/kg (wet weight). Comparable results were obtained during a 30 days exposure experiment with guppy: k ₁ was 41±2L/kg.d, k ₂ 0.014 + 0.002d^‐1, and the bioconcentration factor was estimated to be 2.9 × 10³ L/kg (wet weight).

Four days exposure of rainbow trout larvae resulted in a it, of 22+ 2 L/kg.d, and a k ₂ of 0.031 ±0.007d^‐1. Using these k, and k ₂ values it was estimated that the biconcentration factor exceeds 650 L/kg (wet weight).     

Temperature and salinity adaptation in the purple shore crab Hemigrapsus nudus: An in vitro metabolic flux study with excised gills

The effects of temperature and salinity acclimation on intermediary metabolism in excised gill homogenates from Hemigrapsus nudus were examined. In general, a decrease in salinity was followed by an increase in the oxidation of the substrates glucose-1-¹⁴C, acetate-1-¹⁴C and glycine-¹⁴C to ¹⁴CO₂. Also, there was an increase in amino acid incorporation into the protein fraction. Both of these metabolic parameters were differentially temperature-sensitive. An enzymic model which may explain the increase in respiration rate observed in several intertidal invertebrates meeting an hypo-osmotic stress is proposed, using data from these experiments and also from the literature.     

The composition and biosynthesis of lipids in Thysanoessa raschi from the Clyde Estuary,Scotland

The lipid composition and biosynthesising activity of Thysanoessa raschi collected from the Clyde Estuary, Scotland, in May 1981 were examined. Triacylglycerols were the major lipid class present, although 16.7% of the total lipid were wax esters in which phytol was the dominant fatty alcohol. The thoracic contents (hepatopancreas) of the krill were capable of biosynthesising lipids in vitro from various labelled substrates. Radioactivity from [1-¹⁴C] palmitic acid was incorporated into lipids in the order phospholipids>triacylglycerols>wax esters; the bulk of the radioactivity was present in all cases in the fatty acyl moieties of the lipids. [U-¹⁴C] glucose labelled lipids in the order phospholipids>triacylglycerols>free fatty acids> was esters; in the first two lipids the radioactivity was mainly in the glycerol moieties, whereas in was esters it was solely in the fatty acyl moieties. The extent of labelling of these lipids from [U-¹⁴C] alanine was less than that from [U-¹⁴C] glucose, but the pattern of labelling was generally similar. More than 90% of the radioactivity incorporated into total lipid from ³H₂O was present in free fatty acids from which it was calculated that the hepatopancreas of T. raschi can synthesise 2.5 g of fatty acid per hour at 15°C. This value is approximately three times lower than that previously determined for T. inermis from Balsfjorden, northern Norway. The results are discussed in terms of the sources of the dietary lipids of krill and the role of endogenous biosynthesis in contributing to its lipid reserves.     

离子液体氯化1-辛基-3-甲基咪唑对洋葱的遗传毒性作用

为探讨咪唑类离子液体氯化1-辛基-3-甲基咪唑([C_8mim][C1])对洋葱的遗传毒性,用浓度分别为2.5、5、10和20mmol·L~(-1)的[C_8mim][C1]处理洋葱内表皮细胞和洋葱根尖8 h,用浓度为10 mmol·L~(-1)的[C_8mim][C1]处理洋葱内表皮细胞和洋葱根尖4 h、8 h、12 h和24 h,研究[C_8mim][C1]对洋葱内表皮细胞核的影响和对洋葱根尖有丝分裂指数和染色体畸变的影响。结果显示,与对照组相比,随着[C_8mim][Cl]处理浓度和时间的增加,洋葱内表皮细胞核偏移率明显升高,根尖细胞有丝分裂指数显著降低,染色体畸变现象明显,畸变率升高。研究表明,当浓度达到2.5 mmol·L~(-1)时,[C_8mim][Cl]对洋葱具有遗传毒性。     

Respiratory impairment by water-borne copper and zinc in the edible crab cancer pagurus (L.) (Crustacea: Decapoda) during hypoxic exposure

Specimens of the edible crab Cancer pagurus (L.) collected in the Skagerrak, Denmark, between June and August 1990 were examined in the laboratory. Impairment of respiratory function after pre-exposure (7 d) to sub-lethal concentrations of Cu and Zn (0.4 mg l^-1) was only detectable during hypoxic exposure [PO₂ (partial pressure of oxygen) =60 torr]. This was indicated by a decrease in the transfer factor (TO₂), due principally to an increase in the PO₂ differential across the gills. Cu and Zn exposure did not cause significant changes in ventilation or perfusion although there was some indication that cardiac output may increase in respiratory-impaired individuals. After 28 d exposure no difference was noted in the respiratory responses to hypoxia of treated and untreated crabs. It is concluded that respiratory impairment was due to an increase in the diffusion barrier thickness at the gills and that this was reversible even during continued exposure to trace metal contamination.     

Effect of fomesafen on glutathione S-transferase and cellulase activity and DNA damage in the earthworm (Eisenia fetida)

Biochemical responses and DNA damage of earthworm (Eisenia fetida) exposed to various concentrations of fomesafen (0, 10, 100, and 500 μg kg^?1) for 3, 7, 14, 21, and 28 days were investigated in vivo. Glutathione S-transferase (GST) activity was significantly stimulated upon treatment with 500 μg kg^?1 fomesafen for 21 days, while the cellulase activity was markedly inhibited after 14 days of treatment. On day 28, the activities of GST and cellulase had recovered to the level similar to that of controls. Low or mild DNA damage in earthworm was induced within 14 days of exposure, and the damage was reduced or disappeared with the extension of exposure.     

Wirkung von Isoproturon auf Laich und Larven zweier Unkenarten (Bombina spec.)

In intensively used arable areas, a contamination of the reproduction ponds with pesticides probably impairs the development of spawn and tadpoles of amphibians, based on the coincidental space and time. Therefore, the effects of the herbicide isoproturon (IPU) on the early life stages of the firebellied toad (Bombina bombina) and the closely related yellowbellied toad (Bombina variegata) were investigated. The results of the exposure with¹⁴C-labelled IPU (1 μg/L) indicated an uptake into the spawn and tadpoles of bothBombina species. The jelly capsules could not protect the embryo from effects of the herbicide. Tadpoles with complete opercula and without external gills were most sensitive to contamination by IPU. Physical and behavioral abnormalities of the tadpoles developed at concentrations, of 0.1 μg/L after 24 h exposure. At increasing IPU-concentrations the number of impaired and dead tadpoles increased significantly compared to the control. The enzymatic system of the Glutathion S-Transferase (GST) of theBombina tadpoles were influenced significantly by the duration and concentration of IPU exposure. Compared to the pure active ingredient IPU, the commercial herbicide TOLKAN FLO^® provoked a stronger enzymatic response in the tadpoles. This could be caused by the presence of an emulsifier used in the TOLKAN FLO^® formulation which enhanced the availability of IPU and/or the interaction between IPU and the emulsifier.     

Acid-base responses to lethal aquatic hypercapnia in three marine fishes

Ocean sequestration of CO₂ is proposed as a possible measure to mitigate environmental changes due to the increasing atmospheric concentration of the gas. However, toxic effects of CO₂ on marine organisms are poorly understood. We therefore studied acid–base responses and mortality during exposure to fatal levels of CO₂ in three marine fishes (Japanese flounder, Paralichthys olivaceus; yellowtail, Seriola quinqueradiata; and starspotted dogfish, Mustelus manazo). The teleosts died during exposure to seawater equilibrated with a gas mixture containing 5% CO₂ (water PCO₂ 4.95 kPa); 100% mortality occurred within 8 h for yellowtail and within 48 h for flounder. Only 20% mortality was recorded at 72 h for the dogfish during exposure to 7% CO₂ (water PCO₂ 6.96 kPa). Arterial pH (pH_a) initially decreased, but completely recovered within 1–24 h for the teleosts at 1% and 3%, although the recovery was slower and complete only at 1% (water PCO₂ 0.99 kPa) for the dogfish. During exposure to 5%, the flounder died after the pH_a had been completely restored, suggesting that the mortality was not due to plasma acidosis. During exposure to 1% hypercapnia, plasma [Cl^–] appeared to be the main counter ion to balance increases in plasma [HCO₃^-]. There was a 1:1 stoichiometry for the rise in [HCO₃^-] and the fall in [Cl^–] for the teleosts, whereas the ratio was 1:0.4 for the dogfish at 1% CO₂. At the higher levels of hypercapnia, the rise in [HCO₃^-] consistently exceeded the fall in [Cl^–], and plasma [Na⁺] significantly increased.These results do not agree with the generally accepted model for acid–base regulation in marine fish in which Na⁺/H⁺ exchangers are assumed to play a predominant role, and indicate that an acid–base regulatory mechanism differs between teleost and elasmobranch fishes, as well as the intensity of acidic stress.Communicated by T. Ikeda, Hakodate     

The significance of temperature,salinity and zinc as lethal factors for the mussel Mytilus edulis in a polluted estuary

Mussels, Mytilus edulis L., were subjected to high temperatures, low salinities and dissolved zinc in order to investigate possible environmental hazards of a discharge of heated effluent near Newport on the Yarra River estuary, Victoria, Australia. Exposure to zinc at 0.8 mg l^-1 for 14 d in otherwise favourable conditions significantly increased mortality resulting from subsequent exposure to temperatures between 29° to 31°C for 24 h without added zinc. Mussels collected from water of temporarily lowered salinity (8–16 S) showed significantly lower thermal resistance than controls collected from marine salinities (35 S). Mussels taken from a marine environment and exposed to 10 S died at a rate which increased with temperature. Mussels acclimated for 14 d to combinations of 10°, 16° and 22°C and 22 and 35 S, and subsequently exposed to increased zinc concentrations accumulated zinc to levels which were independent of temperature and salinity. The zinc was lethal more quickly at 22°C and 35 S than at the lower temperatures and salinities. The modes of toxic action of the salinity, zinc and temperature factors are discussed and it is argued that zinc which has been found accumulated in mussels near Newport could be reducing their resistance to raised temperatures and perhaps other stresses, probably as a result of effects on lysosomal functioning. The evidence suggests that the heated effluent will accelerate any toxic effects of zinc or low salinities which occur near Newport and so poses a hazard in winter as well as in summer.     

A unique low molecular weight zinc-binding ligand in the kidney cytosol of the musselMytilus edulis,and its relationship to the inherent variability of zinc accumulation in this organism

Mussels,Mytilus edulis, are known to have a high degree of variability in their whole soft tissue zinc concentrations which cannot be explained by any known ecological or physiological factor. In the present study, 70 individual mussels collected from an uncontaminated site at Bellevue, Newfoundland, in Spring 1987 had kidney zinc concentrations ranging from 148 to 4 907 g g^-1 dry weight while 40 mussel exposed to 25 g l^-1 zinc for 18 d had kidney zinc concentrations ranging from 144 to 14 072 g g^-1. Pooled or individual kidneys were homogenized in 50 mM ammonium bicarbonate buffer (pH 8.0) and ultracentrifuged for 1 h at 105 000 g. On average, about 70% of the total kidney zinc load was found in the 105 000 g pellet. Cytosolic zinc was separated into two peaks on a column of Sephadex G-25. The first peak coincided with the void volume of the column representing molecules with molecular weights of at least 5 000 (exclusion limits of Sephadex G-25). This peak would include any metallothionein present since mussel metallothionein has a molecular weight of 10 000 to 20 000. Little variability was observed in this peak so it was concluded that zinc-thionein did not play a major role in the genesis of the inherent variability. The second peak represented zinc complexed to an unknown substance with an approximate molecular weight of 700 to 1 300. This very low molecular weight zinc showed an extremely high degree of inherent variability and a strong positive correlation with the whole kidney zinc concentration. It is concluded that this very low molecular weight zinc complex plays a major role with regard to kidney zinc variability. Some very low molecular weight zinc was also noted in the digestive gland and gills. It is speculated that this substance may aid in zinc transport as well as in the incorporation of zinc into granules.MSRL Contribution No. 720