AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 1 122-R126, Copyright © 1987 by American Physiological Society
Vasopressin responses to asphyxia and hemorrhage in newborn pigs
C. W. Leffler, D. W. Busija, D. P. Brooks, J. T. Crofton, L. Share, D. G. Beasley and A. M. Fletcher
Vasopressin may be important in maintenance of arterial pressure and
redistribution of cardiac output in hypotensive and asphyxiated newborns.
We used chronically instrumented, unanesthetized, 4-day-old pigs to
investigate the effects of hypotensive hemorrhage and asphyxia on plasma
vasopressin concentration and to determine the effects of cyclooxygenase
inhibition on these responses. Asphyxia [arterial O2 partial pressure
(PaO2) = 40-50 Torr, arterial CO2 partial pressure (PaCO2) = 60-80 Torr)
increases plasma lysine vasopressin (LVP) from 2.2 +/- 0.8 to 52.4 +/- 15.0
microU/ml. Neither the baseline nor stimulated plasma LVP was affected by
indomethacin (5 mg/kg) or meclofenamate (5 mg/kg). Hemorrhage (30 ml/kg)
increased plasma LVP from 2.8 +/- 0.8 to 163.4 +/- 28.1 (20 min) and 135.1
+/- 18.5 microU/ml (60 min). The effects of vehicle and indomethacin (5
mg/kg) 20 min after hemorrhage on plasma LVP 60 min after hemorrhage were
not different. Changes in plasma vasopressin caused by asphyxia and
hemorrhage in the unanesthetized newborn pig are similar to the responses
observed in adults of other species. This study does not suggest that
prostanoids are involved in these responses in newborn pigs.
