The effects of three days of high levels of arginine vasopressin on
the cardiovascular system, extracellular volume and renal function in
fetal sheep.
Gibson, Karen J., and Eugenie R. Lumbers.
School of Physiology & Pharmacology, University of New South
Wales, Sydney, 2052, Australia
APStracts 3:0382R, 1996.
To determine the effects of sustained high levels of arginine
vasopressin (AVP) on the fetus and whether these effects were the
same as those seen during acute infusion of AVP, chronically
catheterized fetal sheep aged 121-136 days were infused for 3 days
with either AVP (45 mU.kg-1.h-1) or with saline. The bradycardia,
acidemia and failure of glomerulotubular balance that occurred with
acute AVP infusion were reversed by Day 3 of AVP (P<0.005) and
the acute rise in arterial pressure was attenuated (P<0.005).
By contrast, the rise glomerular filtration rate was sustained
(P<0.005) and urinary osmolality increased further to 426 + 30
mosm/kg (P<0.01). Although placental blood flow did not change
acutely with AVP, it had fallen by Day 3 (P<0.01). As well,
with AVP but not saline, extracellular volume fell from 588 + 28 to
493 + 29 ml/kg (P<0.002) and the plasma to interstitial volume
ratio rose from 0.18 + 0.01 to 0.21 + 0.01 (P= 0.001). These findings
suggest that although release of AVP may be beneficial in acute
stress in utero, sustained high levels may be detrimental to fetal
health and sodium balance.
Received 6 December 1995; accepted in final form 15 October 1996.
APS Manuscript Number R773-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996