Adrenergic mediation of vasopressin secretion in newborn pigs
Leffler, C.W.; Busija, D.W.; Share, L.; Crofton, J.T.; Brooks, D.P.; Beasley, D.G.; Green, R.S.; Mirro, R.
American Journal of Physiology 253(3 Pt 2): R489-R493
1987
ISSN/ISBN: 0002-9513 PMID: 2820251 Document Number: 293431
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 .mu.U/ml; prazosin = 35.8 .+-. 10.8 .mu.U/ml; and yohimbine = 20.1 .+-. 9.5 .mu.U/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 concentrations, 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 .mu.U/ml) and prazosin-treated (92.6 .+-. 14.2 .mu.U/ml) piglets. In contrast, on hemorrhage of yohimbine-treated piglets, the increase in plasma lysine vasopressin concentration was augmented remarkably (527.0 .+-. 103.2 .mu.U/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.