Role of Adrenal Steroidogenesis in Etiology of Hypertension in the Spontaneously Hypertensive Rat*

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Abstract
We measured peripheral adrenal steroid levels in spontaneously hypertensive rats (SHR), killed by nitrogen suffocation, at different ages during the development of hypertension. SHR became hypertensive by 8 weeks of age. Circulating plasma aldosterone (Aldo) levels of SHR gradually declined with age compared to their male Wistar-Kyoto (WKY) normotensive controls. On the other hand, corticosterone (B) concentrations rose relatively as the rats grew older; however, they were significantly lower in SHR at 16 weeks of age. Deoxycorticosterone (DOC) levels were significantly lower at 8 weeks and 18-hydroxy- 11-deoxycorticosterone (18-OH-DOC) were lower at 16 weeks of age. Steroid ratios at age 4 weeks showed significantly higher B to 18-OH-DOC and lower B to DOC, 18-OH-DOC to Aldo, and 18-OH-DOC to DOC values in SHR. Furthermore, the B to 18- OH-DOC ratio remained significantly higher at 12 weeks and the B to DOC ratio remained lower at 16 weeks. These data imply the possibility of the secretion of an unknown steroid (s) and the existence of another, fourth pathway of Aldo biosynthesis in young SHR. Thus, major alterations of adrenal steroidogenesis exist in young SHR which may be causative in the development of hypertension. After the onset of hypertension, steroidogenesis tends to return to normal, by which time, however, SHR may have developed metacorticoid hypertension.