Role of AVP in the regulation of vascular tonus and blood pressure in patients with chronic renal failure.

This study was undertaken to estimate the role of AVP in the regulation of vascular tonus and blood pressure, at first, during hemodialysis hypotension and, secondly, in hypertensive patients with chronic renal failure (CRF). Study 1: among 12 patients with hemodialysis (HD) hypotension showing similar metabolic and endocrine changes except plasma AVP during HD, 6 who showed an increase in plasma AVP after HD were hemodynamically examined during HD. Gradual decreases in mean BP and cardiac index, and increases in systemic vascular resistance (SVR) and plasma AVP, with a slight time-delay, were observed and thereafter BP inversely showed a slight increase at the end of HD, whereas no significant change in HR was found throughout HD. However, the % change in SVR had a positive correlation with % change in plasma AVP levels (P < 0.01, r = 0.559), but not with that in plasma renin activity or plasma norepinephrine levels. Study 2: oral administration of 100 mg of AVP.V1-receptor antagonist, OPC21268, which completely inhibited the vasoconstriction induced by the exogenously administered AVP, did not show any changes in BP and HR of seven hypertensive CRF patients. However, OPC21268 results in a marked decrease in BP of one hypertensive CRF patient with congestive heart failure (CHF) and nephrotic syndrome. Therefore, in some patients with HD hypotension showing impaired SNS and RAS, AVP may play an important role in the maintenance of BP during HD, predominantly via its peripheral vasoconstrictive action. On the other hand, AVP might not aggressively participate in hypertension of CRF patients, even with relatively high levels of plasma AVP.(ABSTRACT TRUNCATED AT 250 WORDS)