Effect of converting enzyme inhibition on glucocorticoid hypertension in the rat

The renin-angiotensin system was evaluated by inhibition of converting enzyme (CEI) and by testing sensitivity to angiotensin II (AII) in sodium-depleted rats made hypertensive by methylprednisolone (MP), 20 mg/kg im. During a 2-wk period blood pressure rose 38 +/- 4 mmHg (P less than 0.001) in MP and 3 +/- 4 mmHg in controls. After pentobarbital anesthesia, intra-arterial pressure and dose-response curves to AII were determined, before and after SQ14225 (d-3-mercapto-2-methylpropranoyl-l-proline) (1 mg/kg iv). CEI reduced pressure significantly in both MP and controls, although the decrease was smaller in the former (P less than 0.05). Pressor responses to AII were nearly identical in MP and controls and were enhanced to a similar extent by CEI. Ganglionic blockade with pentolinium tartrate, given after CEI, did reduce the pressure in both groups to equal levels. Responses to AII after pentolinium were similar to those obtained after CEI alone. These results indicate that the renin component of glucocorticoid hypertension during sodium deficiency is smaller than that of the normotensive controls. No evidence of glucocorticoid-induced vascular hypersensitivity to AII was detected in this model of experimental hypertension.