Hypertension with Mineralocorticoid Administration to the Long-Evans Rat

Abstract

1. The Carworth Long-Evans rat has been reported to develop adrenal-regeneration hypertension but not deoxycorticosterone acetate (DOCA) hypertension. Deficiency of a hypothalamic receptor for deoxycorticosterone which mediates saline polydipsia has been postulated to underlie this resistance. Since a mineralocorticoid etiology for adrenal-regeneration hypertension has been postulated and all mineralocorticoids are thought to act on common receptors, these previous reports are difficult to reconcile. 2. To determine if an absolute or relative resistance to mineralocorticoids is present, Charles River Long-Evans and Sprague-Dawley rats were given 40 mg (107 micromol) of DOCA pellets/rat or 250 microgrms (0.65 micromol) of 2 alpha-methyl-9-alpha-fluorocortisol/day subcutaneously. 3. Saline polydipsia occurred with both steroids with both rat strains, though significantly less with the Long-Evans rats. Both types of rats became hypertensive and developed cardiac and renal enlargement with both steroids. Hypertension developed more rapidly with 2 alpha-methyl-9 alpha-fluorocortisol. 4. Thus mineralocorticoid hypertension can be produced in the Charles River Long-Evans rat, and the development of adrenal-regeneration hypertension in this rat strain is not incompatible with a mineralocorticoid etiology for adrenal-regeneration hypertension.

Regulation of Blood Pressure During Long-Term Ouabain Infusion in Long-Evans Rats

“…15 Furthermore, Long-Evans rats do not seem to be resistant to mineralocorticoid-induced hypertension, as mineralocorticoid administration leads to similar increases in blood pressure in LongEvans rats, compared with Sprague Dawley rats. 16 Nevertheless, we cannot exclude the possibility that Long-Evans rats may have a different distribution of ␣ isoforms of the sodium pump in comparison to other rat species. Long-Evans rats could have a greater proportion of the ␣ 1 isoform in their vascular smooth muscle, an isoform that is particularly resistant to ouabain.…”