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Journal of Dairy Science Vol. 56 No. 4 436-445
© 1973 by American Dairy Science Association ®
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Hormonal Control of Precursor Pools, Ribonucleic Acid Synthesis, and Cellular Morphology in Mammary Tissue Pieces During Lactogenesis1

H. W. Mohrenweiser2 and R. S. Emery

Departments of Biochemistry and Dairy Science, Michigan State University, East Lansing 48823

ABSTRACT

Ribonucleic acid, deoxyribonucleic acid, and protein content of rat mammary tissue increased between day 18 of pregnancy and day 3 of lactation. Concurrently, free phosphate and nudeoside plus nucleotide pools increased. Preincubation of mammary pieces for 2 to 11 hr in medium without hormone increased specific activity of the nucleosides plus nucleotides compared to those tissue slices incubated with hydrocortisone, prolactin, and insulin. Hormones had no effect on the specific activity of the phosphate pool. Regressive histological changes in tissue pieces incubated 12 hr without hormones were not in tissue incubated in hormone-containing medium.

Increasing the metabolite concentration in the incubation medium enhanced incorporation of 3H-uridine and 32Pi into ribonucleic acid. The combination of insulin, prolactin, and hydrocortisone stimulated ribonucleic acid synthesis in both prepartum and postpartum tissue. Incubation in the presence of prolactin and insulin was sufficient for stimulation in prepartum tissue while hydrocortisone and insulin were necessary for maximum rates of synthesis by postpartum tissue pieces. All species of ribonucleic acid which were identifiable by acrylamide gel electrophoresis responded to hormonal stimulation in a similar manner.

FOOTNOTES

1 Journal Article 5632 from the Michigan Agricultural Experiment Station was supported by a National Institutes of Health Predoctoral Fellowship (5-FLI-GM-3,6,451) and was taken, in part, from a dissertation presented by the senior author to the Graduate School of Michigan State University in partial fulfillment of the requirements for the Ph.D. degree.

2 Present address: McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706.






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Copyright © 1973 by the American Dairy Science Association ®.