| Abstract: | In order to assess the mechanism of the antihypertensive action of progesterone, its effect on blood pressure, plasma volume, extracellular fluid volume, cardiac output and total peripheral resistance was studied in salt loaded 2/3 nephrectomized rats (one kidney and both poles of the remaining one removed) and in salt loaded rats in which in addition to nephrectomy adrenalectomy was also performed. Administration of progesterone (15 mg/kg, s.c., 3 times a week) during the six week course of salt loading significantly (P > 0.01) lowered blood pressure in both nephrectomized and nephrectomized, adrenalectomized rats. When compared to normal, untreated rats both plasma and extracellular fluid volume were found to be elevated in all nephrectomized salt loaded rats. However, no effect of progesterone on body fluid volumes was noted in either nephrectomized or nephrectomized, adrenalectomized rats. Progesterone lowered blood pressure and total peripheral resistance and had no effect on cardiac output in partially nephrectomized, salt loaded rats. The results indicate that: 1. in partially nephrectomized, salt loaded rats progesterone exhibits its antihypertensive action in the absence of mineralocorticoids, 2. in this hypertensive model progesterone does not |
