EFFECTS OF OXYTOCIN, ARGININE-VASOPRESSIN AND LYSINE-VASOPRESSIN ON INSULIN AND GLUCAGON-SECRETION IN SHEEP

The effects of the posterior-pituitary peptides oxytocin (OT), arginin e-vasopressin (AVP) and lysine-vasopressin (LVP) on insulin and glucag on secretion were examined in adult sheep. Each peptide was injected i ntravenously at doses from 1 to 3000 pmol kg(-1). All three peptides i ncreased plasma insulin and glucagon concentrations, but their dose-re sponse relationships revealed differences between them. The maximal in sulin responses induced by OT and AVP were very similar, but the thres hold and maximal doses of AVP for increasing plasma insulin were highe r than those of OT. OT and AVP had the same activity for stimulating g lucagon secretion in respect of the threshold and maximal doses and th e maximal hormone response. LVP also increased plasma insulin and gluc agon concentrations, but it had the weakest activity for stimulating b oth hormones. These results suggest that in sheep posterior-pituitary peptide may play a role in regulating nutrient metabolism by influenci ng pancreatic hormone secretion.