Cyclic Nucleotide Concentrations and Protein Kinase Activities of Bovine Mammary Tissue Maintained in Athymic Nude Mice: Effects of Mammogenic and Lactogenic Hormones

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Abstract
Mammary tissue (4 .times. 4 .times. .3 mm) from five cows was placed subcutaneously in ovariectomized athymic nude mice. After 30 d mice were injected daily for 20 d with saline (controls), 17.beta.-estradiol (1 .mu.g), progesterone (1 mg), or estradiol plus progesterone. Deoxyrobonucleic acid synthesis of bovine ductal epithelium was increased by estradiol, progesterone, or both. Cyclic 3'',5''-adenosine monophosphate concentration of bovine mammary grafts was also increased by estradiol or progesteone. Estradiol increased cyclic 3'',5''-adenosine monophosphate-dependent protein kinase activity and decreased cyclic 3'',5''-guanosine monophosphate concentration in bovine mammary tissue. Progesterone decresed cyclic 3'',5''-guanosine monophosphate-dependent protein kinase activity of bovine mammary tissue. In a second experiment, athymic nude mice bearing mammary tissue from five cows first received 20 d of pretreatment with saline or estradiol plus progesterone. Mice were then injected with saline or hydrocortisone (.2 mg/d) plus bovine prolactin (1 mg/d) for 2 d. Hydrocortisone plus prolactin enhanced .alpha.-lactalbumin production by bovine mammary tissue and had a greater effect in mice that had received estradiol plus progresterone. Pretreatment with estrogen plus progesterone increase tissue cyclic 3'',5''-adenosine and monophosphate and cyclic 3'',5''-adenosine monophospahte-dependent protein kinase and decreased cyclic 3'',5''-guanosine monophosphate and cyclic 3'',5''-guanosine monophosphate-dependent protein kinase. In mice that received estradiol plus progesterone, treatment with hydrocortisone plus prolactin decreased bovine mammary tissue cylcic 3'',5''-adenosine monophosphate and cyclic 3'',5''-adenosine monophosphate-dependent protein kinase but increase tissue cyclic 3'',5''-guanosine monophosphate-dependent protein kinase.