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

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Abstract
The effects of hypophyseetomy and vari- ous hormone replacement therapies upon rates of ribonueleic acid (RNA), deoxyri- bonucleic acid (DNA), casein and cytoplas- nfic protein synthesis, and enzyme activi- ties in lactating rat mammary glands were studied to gain information regarding the functions of eortisol and prolactin in main- taining lactation. Hypophyseetomy re- sulted in decreases in gland weight as well as RNA and DNA levels and rates of syn- thesis. Administration of cortisol partially maintained gland weight, RNA and DNA levels, and RNA synthesis but not DNA synthesis. The maintenance of RNA syn- thesis 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 administra- tion of prolactin which also partially maintained gland weights. Administration of prolactin and eortisol 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 de- creased by hypophysectomy, partially main- tained by eortisol, and apparently main- tained at normal levels by administration of prolaetin and eortisol plus prolactin. En- zyme levels were reduced in hypophysec- tolnized rats receiving oxytoein alone, oxy- tocin plus cortisol, or oxytocin plus pro- lactin. The levels of several enzymes, most notably glucose-6-P dehydrogenase, were maintained by treatment with cortisol plus prolaetin, while the activities of several others were not maintained.

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