Abstract
The possibility of an instability of the HPA axis during development of essential hypertension was examined in spontaneously hypertensive rats (SHR) taken as a model of human essential hypertension. Genetically similar normotensive counter-parts WKY) and normal Wistar-rats served as controls. Investigations were performed at 4, 8, 12 and 16 weeks of age. ACTH and corticosterone (B) were measured by RIA. CRF was assayed by RIA of the ACTH released from dispersed pituitary cells in response to 5 - 6 pooled crude hypothalamic extracts compared to 10 mU of vasopressin. B-response to different doses of ACTH from dispersed adrenal cells was age dependent in all 3 strains. In prehypertensive (4 weeks) SHR-rats the B-response to the lowest ACTH-dose was nearly twice that of the controls. No difference of the in vivo B-response to an ACTH-dose of 0,5 mU/100 g was found in any age-group between the 3 strains. 1 min. exposure to ether resulted in a plasma-ACTH-increase which was significantly higher in SHR-rats at 4 weeks of age. B-increase was only slightly elevated compared to controls. These differences were no more obvious at 12 to 16 weeks of age. CRF-activity in unstressed animals showed no difference neither between age-groups nor between SHR and control animals. A temporary instability of HPA-function is thus supported by these findings and a central dysregulation can be assumed.
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