Cyclic nucleotides, adenylate cyclase, and cyclic AMP phosphodiesterase in mammary glands from pregnant and lactating mice.

In the mammary glands of mice, levels of cyclic AMP increased during pregnancy and then fell precipitously following parturition. In contrast, levels of cyclic GMP fell during the gestation period and then rose rapidly during the early days of lactation. Adenylate cyclase and cyclic AMP hohsphodiesterase activities were elevated during the pregnancy and lactation periods.