Developmental changes in adrenergic regulation of fetal arginine vasopressin secretion.

Abstract

Fetal adaptation to the extrauterine environment is associated with profound alterations in pulmonary, renal, and cardiovascular functions. Coincident with these changes are a variety of endocrine responses including concomitant increases in plasma catecholamine and arginine vasopressin (AVP) levels. In view of the demonstrated interaction between the sympathoadrenal system and the neurohypophysis in adult mammals, we questioned whether increases in plasma catecholamine levels in the fetus affect fetal plasma AVP levels and whether catecholamine-AVP interactions change developmentally. Chronically catheterized fetal lambs at either 131 +/- 1 (preterm) or 142 +/- 1 days (term) received graded infusions of either epinephrine (E) or norepinephrine (NE) at rates of 0.04, 0.2, 0.75, 1.5, and 3.0 micrograms.min-1.kg-1 during successive 40-min infusion periods. Plasma AVP concentrations in term animals significantly increased (1.4 +/- 0.1 to 5.1 +/- 1.6 pg AVP/ml) in response to E infusion of 0.75 microgram.min-1.kg-1 or greater. The log-linear dose response curves for each animal were used to determine the minimum plasma E concentration required to stimulate AVP secretion or "threshold." The mean plasma E threshold for AVP secretion was significantly lower in term animals (1.4 +/- 0.4 ng/ml) than in preterm animals (6.6 +/- 0.9 ng/ml). Plasma E levels were positively correlated with plasma AVP levels (r = 0.90) above the threshold value in both groups. Changes in plasma AVP levels were observed in preterm or term animals in response to NE only at the highest infusion rate studied.(ABSTRACT TRUNCATED AT 250 WORDS)