Action of glucocorticoids on proximal tubule transport systems.

A number of transport systems in the proximal tubule now have been shown to change activity in response to glucocorticoids. Two of them, the Na(+)-H+ exchanger and the Na(+)-dependent phosphate transporter, are apparently directly regulated by specific receptors in the proximal tubule. Glucocorticoid regulation of both transport systems is now known to be dependent upon the synthesis of new mRNA and protein. When one surveys the variety of transporter mechanism and metabolic pathways under glucocorticoid control, it seems clear that this group of hormones usually thought of as controlling glucose metabolism may in fact be playing a central role in maintaining acid-base homeostasis. Future research will clarify this role for glucocorticoids.