Factors Affecting Blood Volumes in Hypophysectomized Female Rats

¹ From the Department of Zoology, Cornell University, Ithaca, New York

Plasma volume by the dye (T-1824) method, hematocrit, hemoglobin concentration and plasma specific gravity were determined, and from them total blood and erythrocyte volumes and plasma protein concentration were derived in hypophysectomized female rats fed standard and enriched diets. The effects of insulin, growth hormone and prolactin were also studied. Hypophysectomy decreased the plasma volume and established a lower, stable plasma volume/body weight ratio which was not influenced significantly by diet or hormones. The erythrocyte volume/body weight ratio markedly reduced after hypophysectomy, was readily increased by the enriched diet, especially in younger animals. Insulin injections did not alter the blood picture or increase the body weight. Growth hormone increased both plasma and erythrocyte volumes proportionally to the elevation in body weight and also increased the total plasma protein. Prolactin, possibly contaminated with growth hormone as noted by the tibia test, acted similarly to growth hormone but to a lesser extent.