Peptide hormones, cytosolic calcium and renal epithelial response

We have reviewed the evidence that a number of hormones interact with renal tubular epithelial cells. The evidence suggests that in the mammalian renal tubule bradykinin and parathyroid hormone interact with cell surface receptors to initiate the hydrolysis of PIP2 leading to the formation of I 1,4,5P3 and diacylglycerol in the distal and proximal tubule, respectively. The activation of this second messenger system leads to the mobilization of Ca2+ from intracellular stores. Vasopressin does not activate this second messenger system in mammalian renal epithelial cells, and we cannot demonstrate I 1,4,5P3 formation and Ca2+ mobilization either in the rabbit papillary collecting tubules or in MDCK cells. There is evidence emerging, but not discussed here, that angiotensin II may also mediate some of its effects on the mammalian proximal tubule via the inositol polyphosphate second messenger system.