Open AccessAdenosine 3′ :5′‐Monophosphate and Hormone Interrelationships in the Mammary Gland of the Rat during Pregnancy and Lactation
Author(s) -
SAPAGHAGAR Mario,
GREENBAUM A. Leslie
Publication year - 1974
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1974.tb03694.x
Subject(s) - lactation , medicine , endocrinology , prolactin , phosphodiesterase , cyclase , hormone , mammary gland , adenosine , biology , enzyme , cyclic adenosine monophosphate , chemistry , pregnancy , stimulation , receptor , biochemistry , genetics , cancer , breast cancer
The activities of adenyl cyclase, the phosphodiesterases of low and high K m and the tissue content of adenosine 3′:5′‐monophosphate (3′: 5′‐AMP) in the mammary glands of rats at different stages of the lactation cycle have been measured. The effect of in vitro F − , Ca 2+ and of the hormones progesterone, β‐estradiol, hydrocortisone, insulin and prolactin on the adenyl cyclase activity of membrane fractions isolated from the mammary glands of pregnant and lactating rats has been investigated. The results show that there is a coordinated change of the activities of the enzymes adenyl cyclase and 3′:5′‐AMP phosphodiesterase and the tissue content of 3′:5′‐AMP at different stages of the lactation cycle with the activity of adenyl cyclase and the level of the cyclic nucleotide rising to a peak at the end of pregnancy and then falling sharply after parturition. The reverse pattern was observed for the 3′:5′‐AMP phosphodiesterase activity. F − (1–10 mM) consistently produced an inhibition (40%) of adenyl cyclase activity of mammary glands from pregnant rats while having no effect on the enzyme from the lactating gland. Low concentrations of Ca 2+ (1 μM) activated the enzyme from pregnant glands and from those of early lactation by about 40% but had little effect on the glands taken from rats of mid‐lactation. Increasing the Ca 2+ concentration led to a decline of this effect and eventual inhibition at 5 mM, the effect being most marked on the fully lactating gland. Progesterone and β‐estradiol consistently caused a considerable stimulation (80 and 50%, respectively) of the adenyl cyclase activity of the pregnant gland; hydrocortisone, insulin and prolactin did not. None of the hormones tested activated the adenyl cyclase activity of the lactating gland and insulin appeared to inhibit it severely. The results, which suggest that the growth and development of the mammary gland is related to the tissue content of 3′: 5‐AMP while the initiation and scale of lactation may be related to its removal, are discussed in relation to development, lactogenesis and milk ejection and the complex endocrine control of these processes.