Inhibitory effect of volatile fatty acids on GRF-induced GH secretion in sheep.

The effect of intravenous infusion of acetate, propionate and butyrate (0, 3, 10, 30 mumol kg-1 min-1 over 40 min) on the secretion of growth hormone (GH), insulin and glucagon in response to growth hormone-releasing factor (GRF) injection (0.25 micrograms/kg, 10 min after the onset of acid infusion) was determined in six sheep. The intravenous injection of GRF caused a marked increase in plasma GH at every dose of each acid. The GH response to GRF was unaffected by an intravenous infusion of acetate. The basal plasma levels of insulin, glucagon and glucose were unchanged by acetate infusion. The infusion of propionate markedly suppressed the GH response to GRF in a dose-dependent manner. Propionate produced increases in plasma insulin, glucagon and glucose concentrations. Butyrate infusion also caused a significant attenuation of GRF-induced GH secretion. Butyrate infusion stimulated the secretion of both insulin and glucagon and caused hyperglycemia. After cessation of the infusion of propionate or butyrate plasma GH tended to increase again. Plasma somatostatin concentrations, which were measured only for the highest dose of butyrate, were unchanged during acid infusion, but increased on discontinuing the infusion. It is concluded that propionate and butyrate suppress GH secretion, while stimulating the secretion of insulin and glucagon in sheep.