MINERALOCORTICOID RECEPTOR SPLICE VARIANTS IN DIFFERENT HUMAN TISSUES

The mineralocorticoid receptor (MR), a member of the steroid receptor family, acts as a transcription factor and mediates both aldosterone a nd cortisol effects. Aldosterone specificity in some tissues results f rom the inactivation of competing cortisol into cortisone by 11 beta-h ydroxysteroid dehydrogenase. In other tissues MR and the glucocorticoi d receptor show overlapping physiological effects or may act together by forming a heterodimer. An additional MR splice variant (MR+4) has b een found in different mRNA samples from rat tissues and human white b lood cells, thereby implying additional modes of MR-regulated effects. We therefore looked for the presence of these two MR-mRNA isoforms in human classical aldosterone target tissues and various other tissues. MR-mRNA was found in all samples investigated, thereby showing the ex pression of MR to be more abundant than has been observed thus far. In addition, the MR+4-mRNA variant was also found in all the tissues exa mined.