Comparative effects of mammalian prolactin and growth hormone on growth in the toads Bufo boreas and Bufo marinus

Abstract

Young (postmetamorphic) toads, Bufo marinus and Bufo boreas, were treated with bovine growth hormone (GH), ovine GH, or ovine prolactin. With a standard, controlled diet, GH caused increased body weight and femur elongation and reduced lipid and glycogen storage indicating lean growth. Ad libitum feeding demonstrated that GH also promotes increased food consumption. Doses of GH as low as 0.3 – 0.6 μg/day were effective in these regards, whereas prolactin did not influence the various aspects of metabolism and growth except at relatively high doses (50–100 μg/day). In view of the high sensitivity to GH, most of the actions of the prolactin injections appear attributable largely to GH contamination, although prolactin may have an independent effect on hepatic glycogen under certain conditions. No diurnal variations were evident in the responses to either prolactin or GH when comparing animals injected in the morning or afternoon.