Hormonal Regulation of Plasma Free Fatty Acid Concentration in Ruminants1,2

Abstract

The effects of seven hormones on plasma free fatty acids (FFA), blood ketones, and blood sugar were studied, using goats as experimental animals. Of the hormones tested, growth hormone caused the most marked increase in plasma FFA. ACTH caused a significant increase in plasma FFA in female goats, but had no effect in castrate males. The catecholamines, epinephrine and norepinephrine, caused an immediate increase in plasma FFA concentration, but the change was not as great as observed in monogastric animals. A glucocorticoid caused slight increases in plasma FFA. All of the above hormones caused increases in concentration of blood sugar, with epinephrine being the most potent. Insulin depressed blood sugar and caused an initial depression of plasma FFA, with the latter recovering to higher than the predicted levels, whereas blood sugar remained depressed. In the females, glucagon had a biphasic effect on plasma FFA, a depression followed by an increase above normal, with an opposite response in blood sugar. The blood sugar response to glucagon was the same in the castrate males, but the plasma FFA did not show the rebound effect. Despite the rather large increases in plasma FFA in some cases, blood ketones were not affected to any great extent by any of the hormones used. Some differences in the magnitude of response due to sex were observed, with the females in general exhibiting greater response than castrate males.