Isotopic Determinations of Blood Volume in Intact and Regenerated Rat Adrenals During Cold Stress

Abstract

Blood volume measurements in intact rat adrenals and 30-day regenerated mesenteric autografts were made by I¹³¹- serum albumin and Cr⁵¹-red blood cell dilution methods before and during exposure to 4 C cold for 1 or 4 hr. These were the intervals at which the greatest changes in glandular and systemic plasma corticoids were observed measured fluorimetrically over a 10-hr period. Transplanted glands from “nonstressed” rats contained 14–18% less blood than intacts, depending upon the method used. Blood volume was increased in both intact and regenerated glands during cold stress, the increase being greater at 4 hr that at 1, and proportionately greater in transplants than in intact glands. Concentrations of plasma and glandular corticoids were similar in intact and regenerated glands in “nonstressed” rats. Although both rose biphasically during stress, the difference between glandular and plasma corticoids was proportionately less for intact than for regenerated glands. These findings suggest that regenerated mesenteric autografts, although able to respond to pituitary stimulation during stress, cannot release formed corticoids normally because of circulatory failure.