Effects of handling, anaesthesia, ovariectomy and adrenalectomy on serial measurements of plasma progesterone in 16-day pregnant rats

Abstract

ABSTRACT The basal concentrations of progesterone in plasma of 16-day pregnant rats were measured after seven different sampling procedures. Progesterone concentrations in serial samples from rats held at the time of sampling (restrained group) were compared with those obtained from rats allowed to remain free in their cage (free group). In addition, the effects on plasma progesterone concentrations of anaesthesia induced by ether or pentobarbitone sodium, and of adrenalectomy and/or ovariectomy were studied. Over the 8-h sampling period, progesterone concentrations in the plasma of restrained rats, with or without anaesthesia, were about 30% higher and more variable than those in free rats. Progesterone concentrations rose sharply over the first 30 min in restrained rats and in those treated with ether. Rats adrenalectomized the day before sampling did not show this early rise and their progesterone concentrations were similar to those of free rats. Progesterone concentrations were lowest in ovariectomized rats which had also been adrenalectomized. These findings show that adrenal secretion can increase plasma concentrations of progesterone in pregnant rats which have been handled or anaesthetized. Such a rise might well modulate the effects of experimental stimuli. J. Endocr. (1984) 100, 189–193