HISTAMINE-EVOKED POTASSIUM RELEASE IN THE MOUSE AND GUINEA-PIG PANCREAS

An investigation was made of the effects of histamine on the K+ concen tration in the effluent in superfused guinea pig and mouse pancreatic segments. The effect of acetylcholine (ACh) was examined for compariso n. Histamine evoked a dose-dependent and transient increase in the Kconcentration in the effluent (K+ release) but is less potent compared to the cholinergic agonist, ACh. At the same doses histamine and ACh evoke a much larger K+ release from mouse superfused pancreatic segmen ts followed in the poststimulus period by a reuptake of K+. However, t his reuptake of K+ was not observed in guinea pig superfused pancreati c segments, On the other hand, the cholinergic antagonist, atropine, c ompletely abolished the K+ release in response to ACh and histamine fr om mouse and guinea pig pancreatic segments. Our results show the invo lvement of histamine in the control of K+ release in pancreatic tissue , with significant differences in the observed responses between speci es.