Influence of suckling and feeding on insulin, gastrin, somatostatin and VIP levels in peripheral venous blood of lactating sows

Abstract

Blood samples were collected in peripheral venous blood of 7 lactating sows, when their piglets were suckling. In 4 of the experiments samples were also taken when the sows were fed a meal. Gastrin, insulin, somatostatin and VIP [vasoactive intestinal polypeptide] levels were measured by radioimmunoassay. Insulin levels increased by .apprx. 100% for about 10 min in response to suckling, in some experiments even before the suckling occurred, i.e., when the sows saw, heard and smelt their piglets. In 4 of the sows suckling caused a biphasic 2-fold increase in gastrin levels, 1 immediate peak which lasted for a few minutes and a 2nd peak of longer duration (about 30-60 min), whereas gastrin levels remained unchanged in 3 animals. Somatostatin levels usually reflected gastrin levels in a reciprocal way. A biphasic decrease of somatostatin levels occurred in the high gastrin responders. Somatostatin levels increased in the experiments in which gastrin levels did not change. Immediate and short-lasting increases of VIP levels were also induced by suckling. Large litters and long suckling periods appeared to be related to greater changes of the levels of all the peptides measured. Feeding influenced insulin, gastrin and somatostatin levels in the same way as did suckling from both a qualitative and a quantitative point of view. VIP levels were not increased by feeding. The possible functional effects of the suckling-induced release of gastrointestinal hormones and possible mechanisms of their release are discussed.