Physiological factors regulating secretion of neurophysin

In pigs serum neurophysin increased immediately following hemorrhage, and it increased threefold above basal concentration 4 minutes after removing 10 per cent of the total blood volume, and decreased gradually towards the basal concentration after reinfusing the blood which had been with-drawn.

Abstract

A radioimmunoassay for serum neurophysin has been developed. In pigs serum neurophysin increased immediately following hemorrhage, and it increased threefold above basal concentration 4 minutes after removing 10 per cent of the total blood volume. It remained elevated for several hours, but after reinfusing the blood which had been with-drawn, serum neurophysin decreased gradually towards the basal concentration. No significant difference in serum concentration of neurophysin was observed in rats of different age, sex, or following ether anesthesia; but the concentration in hypophysectomized rats was one third normal. Serum neurophysin in the external jugular vein was fivefold greater than that in the inferior vena cava. Serum neurophysin increased progressively with the amount of blood removed by hemorrhage and increased more than tenfold upon removing 40 percent of the total blood volume. Prolonged dehydration, ingestion of hypertonic saline, and intravenous infusion of hypertonic solutions caused a significant increase in the concentration of serum neurophysin. An acute reduction in extracellular fluid volume also raised the concentration of serum neurophysin. Thirty minutes after suckling, no change in neurophysin was observed in rats. The rate of release of neurophysin in vitro increased by a factor of 10 when the potassium concentration in the incubation medium was raised from 5.6 mM K+ to 56 mM K+ solution.