Insulin‐stimulated high affinity cyclic AMP phosphodiesterase in rat mammary acini

High affinity cyclic AMP phosphodiesterase activity in preparations of acini isolated from mammary tissue of lactating rats is shown to be stimulated by the addition of physiological concentrations of insulin to incubations of acini in vitro. This effect is expressed specifically on membrane-associated phosphodiesterase and occurs in the absence of concurrent protein synthesis. The possible functional role of this aspect of insulin's action on mammary tissue is discussed and compared with the well-known reversal by this hormone of the effects of lipolytic agents in adipose tissue and liver.