Abstract
Stimulatory effect of serotonin on lactate production of rat diaphragm was examined in Krebs-Ringer bicarbonate solution. At a dose of 50μg per flask, clear-cut effect obtained when incubated with diaphragm from glucose-fed rat, but inconsistent result was noted in diaphragm from fasted rats. When dose of serotonin was raised to 200-250μg, lactate production was stimulated by serotonin without fail even in fasted rat diaphragm. Simultaneous occurrence of enhanced glucose uptake and glycogenolysis was observed when serotonin of high dose (200-250mu;g) was employed, whereas increase in lactate production elicited with 50μg serotonin was never accompanied by augment of either glucose uptake or glycogenolysis. When the amount of lactate produced due to neither enhanced glucose uptake nor glycogenolysis was calculated, effect of serotonin of 50μg was evident in this term in fasted or fed rat diaphragm, suggesting that serotonin, incontrast to insulin or epinephrine, more or less directly increase lactate output from endogenous intermediaries.
