Abstract: 23

IDENTIFICATION AND ONTOGENY OF 11–HYDROXYSTEROID DEHYDROGENASE TYPE 2 ACTIVITY IN BOVINE CORPORA LUTEA.

Freddie N. Kojima^{1 *}, Michael F. Smith^{1 *}, Venkataseshu K. Ganjam^{2 *}
Department of Animal Sciences, University of Missouri, Columbia, MO ¹
Department of Veterinary Biomedical Sciences, University of Missouri, Columbia, MO ²

Fibrillar collagen is a major component of the luteal extracellular matrix. Hydroxyproline content (measurement of collagen content) of bovine corpora lutea (CL) increased during luteal development, concurrent with an increase in circulating concentrations of aldosterone, a stimulator of collagen synthesis. 11–hydroxysteroid dehydrogenase Type 2 (11HSD2; NAD⁺–dependent) is a fundamental “gatekeeper” enzyme, which converts cortisol and corticosterone unidirectionally from active to inactive metabolites, unlike Type 1 (11HSD1; NADP⁺–dependent), which acts bidirectionally. This process of inactivation prevents glucocorticoids from competing with aldosterone for binding to mineralocorticoid–receptors. The objective of this study was to determine if 11HSD2 activity is present in bovine CL and to characterize the ontogeny of 11HSD2 activity during luteal development. Bovine CL were collected via colpotomy on days 2, 4, 5 to 6, 7 to 8, and 9 to 10 post estrus (day 0 = estrus; n = 2–4/time point). In day 10 luteal homogenates, 11HSD2 was the predominant form with a K_m of 10.3 nM; whereas, the K_m for 11HSD1 was in the µM range. 11HSD2 activity on days 2, 4, 5 to 6, 7 to 8, and 9 to 10 was 6.6, 10.7, 50.1, 46.9, and 25.2 pmol/mg protein/h, respectively. 11HSD2 activity was greater (p < 0.05) during days 5 to 9 compared to days 2 and 4. In summary, 11HSD2 was the predominant form in the bovine CL and its activity increased during luteal development. Since 11HSD2 has been co–localized with mineralocorticoid–receptors in most tissues studied so far, aldosterone may have a putative role in CL development and remodeling.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.