Some metabolic and behavioral effects of adrenalectomy on obese Zucker rats

Abstract

Ten-week-old female obese and lean Zucker rats were given access to three separate macronutrient sources (casein, starch, and lard) for 7 days. They were then either adrenalectomized (ADX) or given a sham operation. Rats were assigned to one of three groups and given a daily injection of either 0, 2, or 10 mg of corticosterone. They continued to select a diet for another 17 days, after which they were killed, and their blood was assayed for corticosterone, adrenocorticotropin hormone (ACTH), insulin, glucose, and triglyceride. Retroperitoneal and parametrial fat depots were excised and sampled for lipoprotein lipase activity, fat cell size, and number. Body composition was also determined. Selection patterns of lean and obese rats were markedly affected by both ADX and corticosterone replacement. All three groups of sham-operated obese rats ate significantly more fat than did sham-operated lean rats. Adrenalectomy significantly reduced fat intakes in both obese and lean rats. Corticosterone therapy restored fat appetites of lean and obese rats in a dose-dependent fashion. In comparison to ADX lean rats, ADX obese rats reduced their normally elevated levels of blood glucose, plasma triglycerides, and insulin to within normal limits. Similarly, adipose cellularity of the ADX obese rats was reduced to that of sham-operated lean rats. Carcass fat was significantly reduced after adrenalectomy. Corticosterone therapy prevented the reduction in a dose-dependent way.