Pregnenolone sulphate-independent inhibition of TRPM3 channels by progesterone.
Bottom Line: Progesterone metabolites and 17β-oestradiol were also inhibitory but the effects were relatively small.Corticosteroids lacked effect.Relevance of TRPM3 or the progesterone effect to ovarian cells, which have been suggested to express TRPM3, was not identified.
Affiliation: Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK.Show MeSH
Related in: MedlinePlus
Mentions: We speculated that progesterone regulation of TRPM3 might also be relevant to the female reproductive system where progesterone has potent biological effects. A previous report suggested TRPM3 expression in human ovaries . There were no reports of functional TRPM3 channels in this context and so we investigated if functional channels exist by making whole-cell patch-clamp recordings from granulosa cells freshly isolated from bovine ovarian follicles . In K+-current recording solutions, A-type K+-current was observed (Supplementary Fig. VI), as expected for this cell type . In TRPM3 recording solutions, pregnenolone sulphate evoked large ionic currents but only after delays of several minutes (Fig. 11a, d), which is not expected for TRPM3 (cf.Fig. 3a). The I–Vs of the evoked currents were almost linear (Fig. 11b, e), which is not standard for TRPM3 (cf.Fig. 3b), although has been observed in some recordings . Progesterone did not inhibit the currents evoked by pregnenolone sulphate (Fig. 11a–f). The data suggest that granulosa cells contain ionic currents that are stimulated by pregnenolone sulphate but that these currents may not be mediated by TRPM3 and are not inhibited by progesterone.
Affiliation: Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK.