Enzymatic Activities in Mammary Glands of Several Species

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Abstract
The activities of a number of enzymes in the pathways of energy metabolism and lactose, fat and protein biosynthesis, and DNA levels in guinea pig and cow mammary glands at various stages of pregnancy and lactation, and in sow, mouse, and rabbit mammary glands at full lactation were determined. Large increases in enzyme activities and in DNA levels occurred during early lactation in guinea pig mammary glands but not in cow mammary glands. The significant apparent species differences in enzyme activities observed may have been due to interspecies differences in rates of secretory cell proliferation, in the compositions of the mammary gland samples, or in the inherent nature of the regulatory mechanisms associated with the initiation of lactation. Enzyme levels did not appear to be related to interspecies differences in milk composition.