The effect of pressure on muscle lactate dehydrogenase activity of some deep-sea and shallow-water fishes

The activity of crude muscle lactate dehydrogenase (LDH) of several species of bathypelagic and shallow-water fishes has been measured at pressures between 1 and 578 atm and at temperatures of 15° and 25°C. No relationship has been found between the effect of pressure on enzyme activity and the hydrostatic pressure of the organism's environment. Applied hydrostatic pressure reduced activity at both temperatures. The decrease at 25°C was double the decrease at 15°C in LDH from shallow-water fishes. However, enzymes from 2 bathypelagic fishes showed approximately the same reduction at both temperatures. Thus, the interaction of temperature and pressure was less in deep-sea than in shallow-water fish LDH. Decreasing temperature and increasing pressure would both reduce the activity of LDH. That is, deep-sea conditions are noncompensatory in this instance. It is possible that the dissociation of the effects of temperature and pressure could be an adaptive feature of deep-sea life.This paper is a portion of a thesis submitted to the Graduate School, University of Georgia, in partial fulfillment for the degree of Master of Science.