Pressor response to vasopressin and norepinephrine in DOC-salt hypertensive and prehypertensive rats

Pressor responses to arginine-vasopressin (AVP) and norepinephrine (NE) were studied in deoxycorticosterone (DOC)-salt hypertensive and prehypertensive rats. DOC-salt rats received weekly subcutaneous injection of DOC acetate (30 mg/kg) and given 1% saline for drinking. Salt and control rats received injections of sesame oil and given 1% saline or tap water, respectively. On the 5th day (prehypertensive stage) and at 6th week (hypertensive stage) after treatment had started, pressor responses were studied by measuring changes in mean arterial pressure recorded from the iliac artery in response to i.v. injections of AVP or NE under urethane anesthesia. Pressor response to AVP was enhanced both in DOC-salt hypertensive and prehypertensive rats compared with that in salt and control rats. Pressor response to NE tended to be enhanced in DOC-salt hypertensive rats, however, the enhancement was not observed in the rats in prehypertensive stage. Enhanced pressor response to AVP in DOC-salt prehypertensive rats was not due to the structural change of vascular beds, because peripheral resistance in isolated hindlimb preparations was similar in the three groups. Thus, pressor response to AVP was enhanced even in the prehypertensive stage in DOC-salt rats and the enhancement might be involved in the pathogenesis of hypertension in DOC-salt rats.