Effect of adrenalectomy on rat mammary metabolism.

Rates and patterns of metabolism of specifically labeled glucose, pyruvate, and acetate by mammary slices indicated that rates of glucose metabolism through the Embden-Meyerhof and pentose phosphate pathways and relative pentose cycle activity were decreased by adrenalectomy. Fatty acid synthesis from acetate was not impaired. Capacity to provide reduced nicotinamide adenine dinucleotide phosphate for fatty acid synthesis was not the limiting factor responsible for decreased fatty acid synthesis from glucose in adrenalectomized, lactating rat mammary glands. Oxidation of [1-carbon-14]pyruvate and fatty acid synthesis from [2-carbon-14] pyruvate were not affected by adrenalectomy. Indirect reasoning based upon the data reported led to the suggestion that decreased fatty acid synthesis from glucose after adrenalectomy may have resulted from decreased formation of triose phosphate via the phosphofructose-kinase reaction. It is suggested further that most of the decreases in rat mammary enzyme after adrenalectomy have no direct (causative) relationship to depressed lactational performance after adrenalectomy. Restriction of food intake caused decreased fatty acid synthesis from glucose, pyruvate, and acetate, but relative fatty acid esterification activity was higher than in control and adrenalectomized animals. The effects of adrenalectomy on mammary gland metabolism can be dissociated partially from reduced food intake.