Hemodynamic changes during onset of high-sodium one-kidney figure-8 renal hypertension.

The hemodynamic changes associated with the onset of one-kidney, figure-8, renal-wrap hypertension were monitored in rats fed a high-sodium diet. In addition, the hemodynamic contributions of the sympathetic nervous system (SNS) and arginine vasopressin (AVP) were assessed during the 1st week of hypertension. Renal wrapping caused mean arterial pressure (MAP) to increase significantly from 108 +/- 4 to 140 +/- 4 mmHg on day 5 after renal surgery. The hypertension was associated with a significant bradycardia and no significant change in cardiac output (CO), as measured with an electromagnetic flow probe. Total peripheral resistance (TPR) was significantly elevated to 140% above control value on day 5 after renal surgery. Ganglionic blockade caused similar decreases in MAP and TPR in normotensive and hypertensive animals. Sympathetic blockade after pretreatment with a specific vascular antagonist of AVP, [1-beta-mercapto-beta, beta-cyclopentamethylene propionic acid), 2-(O-methyl)tyrosine]Arg8-vasopressin ([d(CH2)5Tyr(Me)]AVP), caused a greater depressor response in the renal-wrapped animals as compared with the effect of ganglionic blockade alone in these animals. The effect of [d(CH2)5Tyr(Me)]AVP alone on the hemodynamics was not different between the two groups of rats. After ganglionic blockade pretreatment, [d(CH2)5Tyr(Me)]AVP caused a significant decrease in MAP and TPR in the renal-wrapped animals. In addition, the difference in MAP and TPR between the two groups of rats was eliminated after combined blockade of AVP and the SNS. The results of this study indicated that the onset of hypertension was a result of an activation of neurohumoral mechanisms to increase TPR.(ABSTRACT TRUNCATED AT 250 WORDS)