Metabolic actions in intestinal smooth muscle associated with relaxation mediated by adrenergic alpha- and beta-receptors.

Abstract

AbstractIn colonic muscle from the rabbit a relaxing effect was induced by stimulation both of adrenergic α‐receptors with phenylephrine and of β‐receptors with isoprenaline. The α‐receptor induced relaxation was not accompanied initially by any metabolic effects. After a latency period of 3 min did a decrease in the phosphorylase α activity, a decrease in the concentrations of hexose phosphates and lactate and an increase in the concentration of high‐energy phosphate compounds (ATP and CrP) become evident. There was a decrease of the cyclic AMP content. These effects were inhibited by dibenamine. The relaxation induced via adrenergic β‐receptors was preceded by an increase in the cyclic AMP content and the phosphorylase α activity, an increase in the concentration of hexose phosphates and lactate and an initial decrease of the ATP and CrP concentrations, which after 10 min was succeeded by an increase. The magnitudes of the relaxing and metabolic responses following stimulation of preceptors were correlated with regard to time and dose. These responses were blocked by an adrenergic β‐receptor blocking agent (sotalol) and were also eliminated in carbohydrate‐poor muscle. The relaxing and metabolic effects of isoprenaline could be reproduced completely by cyclic AMP, only incompletely by 5'AMP and not at all by other tested cyclic nucleotides.