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Circulating hypotensive factor in pregnant spontaneously hypertensive rats
Clinical and Experimental Pharmacology & Physiology
|March 1, 1981
Summary
A unique factor in pregnant spontaneously hypertensive rats (SHRs) lowers blood pressure late in gestation. This pregnancy-induced hypotensive factor in SHR plasma reduces blood pressure in other rats.
Area of Science:
- Cardiovascular Physiology
- Reproductive Endocrinology
Background:
- Spontaneously hypertensive rats (SHRs) exhibit a significant decrease in blood pressure during late pregnancy.
- This blood pressure reduction typically resolves shortly after parturition.
Purpose of the Study:
- To investigate the cause of the late-pregnancy decrease in blood pressure in SHRs.
- To identify potential hormonal or plasma-borne factors responsible for this hypotensive effect.
Main Methods:
- Hormonal assays were performed for progesterone, prolactin, and estrone.
- Exogenous prostaglandin E2 (PGE2) administration was tested.
- Plasma from pregnant SHRs was administered to both male and female SHRs and Wistar Kyoto rats (WKYs).
Main Results:
- Progesterone, prolactin, and estrone did not appear to cause the observed blood pressure fall.
- Exogenous PGE2 reduced blood pressure, but endogenous prostaglandins (PGE1, PGE2, PGF2 alpha) did not increase in late pregnancy.
- Plasma from pregnant SHRs significantly lowered blood pressure in recipient SHRs, but not in WKYs, and plasma from non-pregnant rats had no effect.
Conclusions:
- A circulating hypotensive factor is present in the plasma of SHRs during late pregnancy.
- This factor appears specific to the hypertensive rat model and pregnancy state.