Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 2003
Publication Date: June 21, 2003
Citation: Connor, E.E., Capuco, A.V., Wood, D.L., Sonstegard, T.S., Mota, A.F. 2003. Ontogenetic regulation of progesterone receptor (pr) expression in bovine mammary gland [abstract]. Journal of Animal Science Supplement. 81 (Suppl. 1): 302. Technical Abstract: The expression patterns of progesterone receptor (PR) mRNA and protein in the bovine mammary gland were characterized during various stages of mammary development and pregnancy. Mammary parenchyma was obtained from prepubertal heifers, pregnant heifers, non-lactating pregnant cows, lactating pregnant cows and lactating non-pregnant cows (n=3 animals/stage). Samples were evaluated for PR mRNA by quantitative real-time RT-PCR and PR protein by western blotting and immunohistochemistry. Results indicated mean PR mRNA abundance was greatest in prepubertal heifers and lactating pregnant cows, but extremely low to non-detectable throughout most of gestation in heifers. Compared to prepubertal heifers, mean expression of PR mRNA was 6-10 times lower in non-lactating pregnant and lactating non-pregnant cows, although expression among non-lactating pregnant cows was highly variable. A similar pattern of expression was reflected in analyses of PR protein. Preliminary results of western blot analysis suggested the presence of two isoforms of PR of approximately 78 and 135 kD, presumably representing PR-A and PR-B, respectively. Quantities of the PR-A and PR-B isoforms differed by physiological state. Our results demonstrate that PR expression in the bovine mammary gland is developmentally and hormonally regulated.