A review of the enzyme activities of plasma membranes reveals that none of them characterize plasma membranes universally. Potentially, adenyl cyclase is the best plasma membrane marker enzyme. Species, tissue and sex differences complicate the sole use of enzymes as markers in the characterization of plasma membrane preparations. It is necessary to establish specific enzymological criteria for plasma membrane enzymes to distinguish them from isoenzymes in other subcellular membranes. Standard assays have been suggested for comparative purposes.

The effects of androgens on lipid transport and metabolism have been reviewed. These effects are probably independent of the androgenic and anabolic activities of the androgens, although the molecular mechanism of action is still not known. Presumably the lowering by androgens of the concentrations of serum lipids and lipoproteins could be the consequence possibly of a primary, inhibitory effect on the synthesis of apolipoprotein A. In addition the role of increased lipolytic activities in plasma and of effects on intermediatry metabolism has been considered.

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