Effects of Hypophysectomy and Several Hormone Replacement Therapies upon Patterns of Nucleic Acid and Protein Synthesis and Enzyme Levels in Lactating Rat Mammary Glands

Abstract

The effects of hypophysectomy and various hormone replacement therapies upon rates of ribonucleic acid (RNA), deoxyribonucleic acid (DNA), casein and cytoplasmic protein synthesis, and enzyme activities in lactating rat mammary glands were studied to gain information regarding the functions of cortisol and prolactin in maintaining lactation. Hypophysectomy resulted in decreases in gland weight as well as RNA and DNA levels and rates of synthesis. Administration of cortisol partially maintained gland weight, RNA and DNA levels, and RNA synthesis but not DNA synthesis. The maintenance of RNA synthesis by cortisol appeared to be specific in that only the synthesis of one of the two RNA fractions studied was maintained. Deoxyribonucleic acid levels and rates of synthesis were maintained by administration of prolactin which also partially maintained gland weights. Administration of prolactin and cortisol together resulted in the maintenance of apparently normal gland weights and RNA and DNA levels and rates of synthesis. Rates of casein and cytoplasmic protein synthesis were decreased by hypophysectomy, partially maintained by cortisol, and apparently maintained at normal levels by administration of prolactin and cortisol plus prolactin. Enzyme levels were reduced in hypophysectomized rats receiving oxytocin alone, oxytocin plus cortisol, or oxytocin plus prolactin. The levels of several enzymes, most notably glucose-6-P dehydrogenase, were maintained by treatment with cortisol plus prolactin, while the activities of several others were not maintained.