KONRUEB, G . O., and BALDWIN, R. L. Hormonal regulation of rat mammary gland enzyme activities and metabolite patterns. Can. J. Biochem. 50, 377-385 (1972).A~tivities s f nine enzymes and the levels of 15 metabolites were determined in mammary glands from normal (N) and adrenalectsmized-ovariectomized (80) rats in midlactation. Mammary gland weights and mammary DNA did not change between day 11 and day 89 of lactation in N animals and were not affected appreciably by AO. Four days after A 0 the activities of citrate cleavage enzyme, malic enzyme, UDPglucose pyrophosphoryhse, the A protein sf t h lactose synthetase complex, and glucose-6-phosphate dehydrogenase were decreased to 24,59, 53, 52, and 56% of day 2 1 N. These same enzymes require cortisol therapy to increase in activity after adrenalectomy on the 5th day sf lactation. Activities of phosphoglucomutase, dphosghsgluconate dehydrogenase, fructose-156-diphospkate aldohse, and isocitrate dehydrogenase were not &wted by AO. These enzymatic changes are discussed in relation to systems regulating milk synthesis. Mammary glucose levels increased 1.9-fold in A 0 animals. Leveb of triose phosphate, a-glycerol phosphate, and aspartate in A 0 animals were decreased to 52, 49, and 62% of N. The proportion of highenergy phosphate bonds to total adenine nucleotides was not affected by AO. Ratios of [free NADP]/[free NADPH,] were not significantly affected by A 0 or stage of lactation. Metabolite patterns are discussed in rehtion to changes in enzyme activities and in uitrs tracer data.