Effect of the adrenocorticostatic agent, metopirone, on thermoregulatory heat production in the European hedgehog*.

1. Non-shivering thermogenesis (NST) was studied in 8 hedgehogs before and after a single injection of metopirone ditartrate (150-450 mg/kg, i.p.) at a thermoneutral chamber temperature (Ta) of 28C and during cold exposure (Ta = 8 degrees C for 20 min). 2. An average metabolic increase of 149% of the standard metabolic rate (SMR) was observed 12-26 min after an injection of metopirone ditartrate at thermoneutral chamber temperature. Average temperatures simultaneously increased by 2.1C in the brown adipose tissue (BAT) and 2.0C in the deep colon. This initial effect lasted for 40 plus or minus 8 min. 3. In a period of 3-48 h after injection of metopirone ditartrate, cold-induced NST was reduced by 89% of SMR (av.). Concomitant exposure to cold caused average temperatures to decrease by 1.0C in the BAT and 1.1 C in the colon relative to control experiments. 4. Our results suggest the participation of corticosteroids in the control of NST in the hedgehog. As metopirone blocks enzymatic 11 beta-hydroxylation in the steroid ring, there is a pronounced increase of endogenous 11-deoxycorticosteroids, such as deoxycorticoterone (DOC). An injection of DOC (3 mg/kg, i.m.) increases NST at hermoneutrality similar to the initial metabolic effect elicited by metopirone ditartrate. The reduced response to cold exposure after several hours may be explained by competitive inhibition of glucocorticoid receptors since there is also an increased production of other 11-deoxycorticosteroids.