Sensitivity of the renal medullary circulation to plasma
vasopressin.
Franchini, Kleber G., and Allen W. Cowley, Jr.
Heart Institute, University of Sao Paulo, Sao Paulo, Brazil,
Department of Physiology, Medical College of Wisconsin, Milwaukee,
WI
APStracts 3:0143R, 1996.
Studies were carried out to determine the effects of physiological
changes of plasma arginine vasopressin (AVP) upon blood flow
distribution in the renal cortex and medulla. Acute decerebration was
performed so that studies could be carried out within the low
physiological range of circulating AVP. Changes of renal cortical and
medullary microcirculatory blood flow were measured with implanted
optical fibers and laser-Doppler flowmetry and total renal blood flow
with transit-time ultrasonography. During intravenous infusion of
increasing doses of AVP, when plasma AVP was increased in steps from
2.9 to 11.2 pg/ml by intravenous infusion, mean arterial pressure
(98+/-3 mmHg), total renal blood flow (8.2+/-0.6 ml/min/g kidney),
and blood flow in the microcirculation of the cortex (2.11+/-0.28 V)
remained unchanged, while that in the renal medulla decreased
progressively. Medullary flow was significantly reduced when
circulating levels of AVP increased from a control level of 2.8 pg/ml
to 5.0 pg/ml. The reductions of medullary flow were accompanied by
parallel increases of urine osmolality. These data indicate that the
vessels supplying the renal medullary circulation are sensitive
within the range of plasma AVP concentrations observed with moderate
water restriction. The medullary circulation exhibits a sensitivity
to AVP which parallels that found in the medullary collecting ducts.
Received 18 December 1995; accepted in final form 8 March 1996.
APS Manuscript Number R796-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 23 April 96