Progesterone rapidly reduces arterial pressure in ewes
Roesch, D.M.; Keller-Wood, M.
American Journal of Physiology 272(1 Pt 2): H386-H391
1997
ISSN/ISBN: 0002-9513 PMID: 9038960 Document Number: 470626
Chronic progesterone treatment decreases mean arterial pressure (MAP) and expands plasma volume. Evidence now suggests that progesterone metabolites have rapid nongenomic actions on the baroreflex. This experiment tests for a rapid effect of progesterone on MAP, Na+, arginine vasopressin, and baroreflex sensitivity, Ewes were studied during 2-h infusions of vehicle or progesterone at 3 and 6 mu-g cntdot kg-1 cntdot min-1. Infusion of progesterone at 3 mu-g cntdot kg-1 cntdot min-1 resulted in progesterone levels characteristic of ovine pregnancy and significantly reduced MAP by the 17th minute, suggesting a nongenomic mechanism. However, progesterone infusion at 6 mu-g cntdot kg-1 cntdot min-1 produced supraphysiological progesterone levels and failed to modify MAP. Overall baroreflex sensitivity was not altered by either dose of progesterone, but the slope of the tachycardic response to hypotension tended to be attenuated after infusion of progesterone at 6 mu-g cntdot kg-1 cntdot min-1. We speculate that the lack of a simple, linear dose-response effect of progesterone on blood pressure and baroreflex sensitivity can be explained by progesterone action at multiple receptor populations.