Item – Theses Canada

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OCLC number
46496012
Author
Wang, Hui Di,1962-
Title
The role of kidney in the antihypertensive effect of vasopressin.
Degree
Ph. D. -- University of Saskatchewan, 1995
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, 1995.
Description
2 microfiches.
Notes
Includes bibliographical references.
Abstract
Previous studies have shown that cessation of a three hour infusion of arginine vasopressin (AVP: 20 ng/kg/min) was associated with a dramatic and prolonged decrease in blood pressure (BP) below pre-infusion basal levels in hypertensive rats, but not in normotensive rats. This phenomenon has been termed as the "withdrawal-induced antihypertensive phenomenon"(WAP). The work described in this thesis was designed to test the hypothesis that the mechanism of the WAP was related to renal function, specifically an increase in sodium excretion during the infusion of AVP. In deoxycorticosterone acetate (DOCA)-salt hypertensive rats, cessation of the 3 hour infusion of AVP was associated with a large WAP in rats with kidneys but not in anephric rats indicating the importance of the kidney in the mechanism of the WAP. In rats with intact renal function, cessation of the AVP infusion was associated with a large fall in pressure below pre-infusion basal levels in hypertensive rats but not in normotensive rats, nor in hypertensive rats following cessation of an equipressor dose of phenylephrine (PE). Sodium excretion rates increased markedly during the infusions of AVP and PE in DOCA-salt hypertensive rats and normotensive controls, but the natriuresis was greater for AVP than for PE. Urine flow increased during AVP and PE infusions to a similar extent. Furosemide induced a significant fall in BP in DOCA-salt hypertensive rats, although the decrease was not as large as that observed after AVP. Furosemide did not induce a fall in BP in normotensive rats. Replacement of the sodium losses that had occurred during the AVP infusion increased BP towards pre-infusion control values in DOCA-salt hypertensive rats, although the increase was not large enough to completely restore BP to the pre-infusion levels. In spontaneously hypertensive rats (SHR) rats, cessation of the three hour-infusion of AVP was also associated with a dramatic fall in BP below pre-infusion levels, but not in their Wistar-Kyoto (WKY) normotensive counterparts. Sodium excretion and urine flow increased in both SHR and WKY rats to a similar degree. Although furosemide induced either a similar or greater degree of sodium loss and urine flow than did the infusion of AVP, the diuretic failed to induce any changes in BP in both SHR or WKY rats. Replacement of the sodium losses that had occurred during the AVP infusion failed to return BP towards control levels in SHR. The results indicate a major difference between the SHR and DOCA-salt hypertensive models in relationship to the contribution of sodium losses to the magnitude of the WAP. In SHR, sodium losses do not account for the antihypertensive effect of AVP. In contrast in the DOCA-salt hypenensive model, sodium losses appear to contribute significantly to the WAP, although other factors must also contribute in order to fully account for the magnitude of this effect.
ISBN
0612002659
9780612002654