THE CONCENTRATIONS OF SOME GUT POLYPEPTIDES ARE ELEVATED DURING LACTATION IN RUMINANTS

Circulating concentrations of both glucose-dependent insulinotropic po lypeptide (GIP) and glucagon-like peptide-1 (7-36)amide (GLP-1) were d etermined in dry and lactating sheep. Both polypeptides were significa ntly higher in lactating animals compared with dry. The half-life of b oth in plasma was determined by intravenous injection of GIP or GLP-1 in both dry and lactating animals, but neither peptide showed a signif icantly different value during lactation. Thus, the increased circulat ing concentrations during lactation must result from increased secreti on, probably resulting from the increased feed intake during lactation . Serum insulin concentrations were significantly lower during lactati on, which poses the question of how lactating animals maintain lower c irculating insulin levels in the presence of higher levels of insulino tropic agents. (C) 1997 Elsevier Science Inc.