Progesterone rapidly reduces arterial pressure in ewes.
Roesch, Darren M., and Maureen Keller-Wood.
Department of Pharmacodynamics, College of Pharmacy, University of
Florida, Gainesville, Florida 32610-0487
APStracts 3:0324H, 1996.
Chronic progesterone treatment decreases mean arterial pressure (MAP)
and expands plasma volume. Evidence now suggests progesterone
metabolites have rapid nongenomic actions on the baroreflex. This
experiment tests for a rapid effect of progesterone on MAP, Na+,
arginine vasopressin (AVP), and baroreflex sensitivity. Ewes were
studied during two-hour infusions of vehicle or progesterone at 3 and
6 [mu]g/kg/min. Infusion of progesterone at 3 [mu]g/kg/min resulted
in progesterone levels characteristic of ovine pregnancy and
significantly reduced MAP by the seventeenth minute, suggesting a
nongenomic mechanism. However, progesterone infusion at 6
[mu]g/kg/min 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 6
[mu]g progesterone/kg/min. 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.
Received 7 November 1995; accepted in final form 11 July 1996.
APS Manuscript Number H1041-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 21 August 1996