Involvement of β1- and β2- but not β3-adrenoceptor activation in adrenergic PYY secretion from the isolated colon

Abstract

The secretion of PYY by endocrine L cells of the terminal gut is under the control of nutrients, the autonomic nervous system and hormones. Catecholamines, and the non-specifc β-adrenergic agonist isoproterenol induce PYY secretion from rat isolated colon or ileum. Because β3-adrenergic receptors now appear to mediate many of the effects of catecholamines in the gastrointestinal tract, we investigated the involvement of β1-,β2-, and β3-adrenoceptor stimulation in PYY secretion from the isolated, vascularly perfused rat colon. Infusion of 10-6 M isoproterenol induced a transient increase in PYY secretion (from 36 ± 4 to 87 ± 20 fmol/2 min; n=7, P<0.05), that was abolished by a previous infusion of the β1- and β2-adrenergic blocker (and partial β3-agonist) alprenolol (10-6 M). The β1-adrenergic agonist dobutamine and the β-2 agonist terbutaline also (both at 10-5 M) significantly stimulated PYY secretion, from 29 ± 1 to 79 ± 12 fmol/2 min and from 19 ± 1 to 73 ± 13 fmol/2 min respectively (n=7, P<0.05). Neither of the β3-adrenergic agonists tested (BRL 37 344 (10-5, 10-6 M) and SR 58 611A (10-6 M)) significantly stimulated PYY secretion, thus confirming the exclusive involvement of β1- andβ2-receptors in β-adrenergic agonist induced hormone secretion.