Mechanisms of Ion Transport Regulation by Parathyroid Hormone: cAMP/Ca2+/Calmodulin and Phospholipid Dependent Phosphorylation
Since 1976, when the function of the Na+ dependent phosphate symport of the renal brush border membrane (BBM) was first well described, numerous regulatory mechanisms of renal phosphate transport have been shown to exert effects on this carrier protein similar to their affect on proximal tubular phosphate transport (1,2). Parathyroid hormone (PTH), which decreases renal phosphate reabsorption, also causes a decrease in Na+ dependent phosphate transport in isolated brush border membrane vesicles (BBMV) (3,4). This effect is exerted as a decrease in the Vmax of the carrier activity compatible with a mechanism acting through a decrease in the number of membrane functional units or a decrease in the overall activity of existing units. The mechanism of action of PTH has long been thought to occur through stimulation of adenylate cyclase, increasing c-AMP, and activation of a c-AMP dependent protein kinase (5,6).
KeywordsPhosphatidic Acid Brush Border Membrane Dependent Protein Phosphate Transport Dependent Protein Kinase
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