0000000000749545
AUTHOR
Michael Thuy
Heat production of frogs under normoxic and hypoxic conditions: A microcalorimetric study using a gas flow system
Abstract Heat production of male frogs, Rana temporaria , was measured in a microcalorimeter through which a continuous flow of gas was passed in order to generate constant normoxic, hypoxic or anoxic conditions. The normoxic heat flow was 163 ± 37 μ W g body weight in frogs that had not been treated with curare and 149 ± 69 μ W g in animals immobilized with curare. During anoxia, frogs, whether curarized or not, decreased their heat production to about 25% of the respective normoxic control. In graded hypoxia (10% to 3% O 2 ), curarized frogs decreased their heat rate according to the grade of hypoxia they were subjected to.
Fructose 2,6-bisphosphate and glycolytic flux in skeletal muscle of swimming frog
AbstractGlycolytic flux in skeletal muscle is controlled by 6-phosphofructokinase but how this is achieved is controversial. Brief exercise (swimming) in frogs caused a dramatic increase in the phosphofructokinase activator, fructose 2,6-bisphosphate, in working muscle. The kinetics of phosphofructokinase suggest that in resting muscle, the enzyme is inhibited by ATP plus citrate and that the increase in fructose 2,6-bisphosphate is part of the mechanism to activate phosphofructokinase when exercise begins. When exercise was sustained, fructose 2,6-bisphosphate in muscle was decreased as was the rate of lactate accumulation. Glycolytic flux and the content of fructose 2,6-bisphosphate appea…