AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 3 489-R493, Copyright © 1987 by American Physiological Society
Adrenergic mediation of vasopressin secretion in newborn pigs
C. W. Leffler, D. W. Busija, L. Share, J. T. Crofton, D. P. Brooks, D. G. Beasley, R. S. Green and R. Mirro
Effects of inhibition of alpha 1-(prazosin) and alpha 2-(yohimbine)
adrenoreceptors on plasma lysine vasopressin concentration during
normotension and hemorrhagic hypotension were studied in unanesthetized
newborn pigs. During the normotensive period, treatment with prazosin and
yohimbine both increased plasma lysine vasopressin concentration (vehicle =
3.4 +/- 1.21 microU/ml; prazosin = 35.8 +/- 10.8 microU/ml; and yohimbine =
20.1 +/- 9.5 microU/ml). Prazosin caused a decline in arterial pressure
(vehicle = 60 +/- 6 mmHg; prazosin = 49 +/- 5 mmHg), which may account for
the increase in plasma lysine vasopressin concentration, whereas yohimbine
increased arterial pressure (73 +/- 3 mmHg). On hemorrhage to equivalent
arterial pressure, plasma lysine vasopressin concentration increased to
similar levels in vehicle- (110.3 +/- 28.7 microU/ml) and prazosin-treated
(92.6 +/- 14.2 microU/ml) piglets. In contrast, on hemorrhage of
yohimbine-treated piglets, the increase in plasma lysine vasopressin
concentration was augmented remarkably (527.0 +/- 103.2 microU/ml) in
comparison to the other groups. We conclude that, in unanesthetized newborn
pigs, treatment with the alpha 2-adrenoreceptor antagonist yohimbine
increased plasma lysine vasopressin concentration and markedly accentuated
the vasopressin response to hemorrhage. An alpha 2-adrenergic
receptor-mediated mechanism appears to be an important inhibitory component
in the vasopressin secretory system of the newborn pig.
