Adrenergic signal transduction in the kidney

During signal transduction, renal adrenoceptors associate with (as in other tissues) specific members of a family of GTP-binding (G) proteins. Renal beta-adrenoceptors activate adenylate cyclase in glomeruli and distal nephrons via an interaction with the stimulatory G protein Gs. alpha 1-Adrenoceptors bind to an as yet uncharacterized G protein and activate phospholipase C to produce the putative second messengers 1,4,5-inositol trisphosphate and diacylglycerol. alpha 1-Adrenoceptors are found in most segments of the nephron where they regulate sodium reabsorption, and metabolic functions such as gluconeogenesis. Renal alpha 2-adrenoceptors which inhibit adenylate cyclase through the inhibitory G protein Gi are located mainly in the proximal convoluted tubule and the collecting ducts. Another population of alpha 2-adrenoceptors has been identified which enhances the sodium-hydrogen exchange across the luminal membrane of proximal tubules. Ongoing research is clarifying the locations and functions of these renal adrenoceptor subtypes.