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Cyclic Nucleotide Concentrations and Protein Kinase Activities of Bovine Mammary Tissue Maintained in Athymic Nude Mice: Effects of Mammogenic and Lactogenic Hormones¹

Dairy Science Department, University of Wisconsin, Madison 53706

Clifford W. Welsch

Department of Anatomy, Michigan State University, East Lansing 48824

ABSTRACT

Mammary tissue (4 x 4 x .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), 17ß-estradiol (1 µg), 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 progesterone. Estradiol increased cyclic 3',5'-adenosine monophosphate-dependent protein kinase activity and decreased cyclic 3',5'-guanosine monophosphate concentration in bovine mammary tissue. Progesterone decreased 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 -lactalbumin production by bovine mammary tissue and had a greater effect in mice that had received estradiol plus progesterone. Pretreatment with estrogen plus progesterone increased tissue cyclic 3',5'-adenosine and monophosphate and cyclic 3',5'-adenosine monophosphate-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 cyclic 3',5'-adenosine monophosphate and cyclic 3',5'-adenosine monophosphate-dependent protein kinase but increased tissue cyclic 3',5'-guanosine monophosphate-dependent protein kinase.

¹ Supported by University of Wisconsin College of Agricultural and Life Sciences, Hatch Grant 3108, and Grant HD-17331 from the National Institutes of Health. Bovine prolactin provided by the National Pituitary and Hormone Program of the National Institutes of Health.