Corticosteroid dynamics in the nonpregnant, pregnant, and postpartum spontaneously hypertensive rat

Factors responsible for hypertension in the spontaneously hypertensive rat (SHR) remain under investigation. As in human pregnancy complicated by esse ntial chronic hypertension, the hypertension of the pregnant SHR subsides a nd returns postpartum Because corticosteroid excess can cause hypertension, we examined several aspects of adrenocortical activity as potentially affe cting the reported blood pressure profiles of nonpregnant, term pregnant, a nd postpartum SHR, using normotensive Wistar-Kyoto (WKY) rats as controls. We found that corticosterone levels were comparable in nonpregnant SHR and WKY rats, and unaffected by pregnancy. No differences were detected postpar tum. Although pregnancy was accompanied by significant increases in plasma aldosterone levels, no interbreed differences were observed, which remained the case postpartum. Single adrenal cell secretion of aldosterone and cort icosterone, as detected by reverse hemolytic plaque assay, yielded similar results in the pregnant and postpartum rat. Hormone responses to dietary ma nipulations in the nonpregnant and pregnant SHR and WKY suggest an importan t role for ACTH, and a lesser one for AII in the regulation of corticostero ids. In situ hybridization histochemistry, using a probe that detects both P450c11 beta and P450c11AS mRNA, revealed comparable message density and zo nal distribution in adrenals from pregnant and nonpregnant SHR and WKY rats . Breed- and pregnancy-dependent differences in adrenal expression of P450s cc, P450c11 beta, and P450c11AS were noted. In summary, our findings sugges t that although some discrepancies exist in the aspects of adrenocortical a ctivity examined, they are unlikely to be etiologic in the blood pressure p rofile observed in nonpregnant, pregnant, and postpartum SHR. (C) 2000 Amer ican Journal of Hypertension, Ltd.