CORTICOTROPIN EFFECTS ON BLOOD-PRESSURE AND FLUID AND ELECTROLYTE HOMEOSTASIS IN 5 STRAINS OF RATS

The hemodynamic and metabolic effects of 11 days of sham (saline) and corticotropin injection were examined in five different strains of rats: Sprague-Dawley, spontaneously hypertensive (SHR), Wistar-Kyoto (WKY), Brattleboro, and Long Evans. Corticotropin significantly increased systolic blood pressure (SBP) compared with sham injection in all strains: final SBP in Sprague-Dawley was 108 +/- 5 mm Hg corticotropin, 94 +/- 4 mm Hg sham; SHR 146 +/- 6 mm Hg corticotropin, 141 +/- 3 mm Hg sham; WKY 117 +/- 3 mm Hg corticotropin, 103 +/- 3 mm Hg sham; Brattleboro 108 +/- 5 mm Hg corticotropin, 93 +/- 2 mm Hg sham; and Long Evans 103 +/- 5 mm Hg corticotropin, 90 +/- 4 mm Hg sham (P < .001). Corticotropin also produced a decrease in body weight and increases in water intake and urine out put. Increases in urine electrolyte excretion were seen in some, but not all strains. The rise in pressure in the Brattleboro rats indicated that vasopressin is not essential for the corticotropin-induced rise in pressure. Blood pressure rises in SHR were not exaggerated. Withdrawal of corticotropin in Sprague-Dawley rats led to rapid reversal of the corticotropin-induced hemodynamic and metabolic changes. Thus, strain does not appear to be an important factor in corticotropin hypertension in the rat, in contrast to deoxycorticosterone hypertension.