GROWTH-HORMONE CONCENTRATIONS IN MAMMARY SECRETIONS AND PLASMA OF THEPERIPARTURIENT BITCH AND IN PLASMA OF THE NEONATE

The presence of growth hormone (GH) in mammary secretions of bitches w as investigated in relation to plasma GH concentrations at about the t ime of parturition and during the first weeks of lactation. Plasma GH concentrations in neonates were measured during the first weeks of lac tation to determine whether GH in maternal milk contributes to plasma concentrations of GH in the neonate. Gastrointestinal uptake of GH was studied by measurement of plasma bovine GH (bGH) concentrations after intragastric administration of bGH. High concentrations of GH were fo und in the mammary secretions of the bitches, particularly before part urition and in colostrum, exceeding maternal plasma concentration up t o 100-1000 times. GH concentrations in milk were not significantly cor related with GH concentrations in plasma of bitches or neonates. Bovin e GH could not be detected in neonatal plasma for 4 h after intragastr ic administration of bGH. The presence of high concentrations of canin e GH (cGH) in ante-partum and colostral mammary secretions is consiste nt with the progesterone-induced mammary biosynthesis of GH. GH in mil k is probably not absorbed from the gastrointestinal tract into the bl ood circulation of the newborn in its intact form.