Biochemistry and physiology of alligator metabolism in vivo

Abstract

The metabolic rate of the alligator is a direct function of the volume of blood flowing through the capillaries/unit time/unit weight, which in turn, is determined by the heart rate and the stroke volume. For an animal with such a low metabolic rate, the heart rate is relatively rapid, in part because the heart is relatively small. Metabolic rate of the smallest alligator exceeds that of the largest by about 25 to 1. Lowering the temperature decreases blood flow without decreasing the oxygen and substrate extracted from each liter. Metabolic rate (oxygen consumption) is expressed by the equation M.R. = F(A - V), where F is the blood flow and A - V is the oxygen A - V difference. For the catabolism of compounds in which oxygen is not directly involved, the expression is V = KF[S], where V is the velocity of the reaction, F is the blood flow, and [S] is the concentration of the substrate. K is a constant, differing for each catabolite, but having about the same value for any one catabolite in vertebrates, cold- or warm-blooded. Enzyme kinetics in a live vertebrate has little in common with that determined in the usual experiments in vitro. A 70 kg alligator at 28°C has a blood flow of 0.2 liters/min, a stroke volume of 6.3 ml, a circulation time of 27 min, and it produces about 72 kcal/day, or about 4% of that of a man of equal size. © 1989 by the American Society of Zoologists.