Endocrine Abstracts

1,25-hydroxyvitamin D3 receptors (VDR) are present on rat granulosa cells and on human ovarian cancer cells, however little is known about 1,25-hydroxyvitamin D3 (1,25-(OH)₂D3) function in the ovary. Vitamin D deficient rats have reduced fertility, and VDR null mutant mice demonstrate impaired folliculogenesis. Vitamin D metabolites have been detected in follicular fluid.

The aim of this study was to investigate the effect of a range of concentrations of 1,25-(OH)₂D3 (2pM-20nM) on luteinised granulosa cells from IVF collections, or pooled unstimulated cells from small follicles. Cells were plated at concentration of 5x10⁵ per well, and cultured in McCoys 5A modified medium. In the luteinised cells, 1,25-(OH)₂D3 suppressed the production of oestradiol (E2) in a dose-responsive manner over 48 to 96 hours: median inhibition was 25% (range 0-70%). The lowest effective concentration was 20pM. LH-stimulated (5-10ng/ml) production of E2 was also inhibited: median inhibition 35% (range 5-50%). The production of progesterone (P) increased or was unchanged. In contrast, the effects on granulosa cells from small (<10mm) unstimulated follicles were variable. Vitamin D had little or no effect on baseline steroid production, but enhanced gonadotrophin stimulated P and E2 production.

In summary, 1,25-(OH)₂D3 inhibited both basal and LH mediated E2 production by luteinised granulosa cells. In granulosa cells from small follicles, gonadotrophin-mediated steroidogenesis was enhanced. In conclusion, 1,25-(OH)₂D3 may have a role in modulating folliculogenesis.