CELL CA2+ RESPONSE TO LUMINAL VASOPRESSIN IN CORTICAL COLLECTING TUBULE PRINCIPAL CELLS

Although vasopressin V-1 receptors have been shown to exist in both luminal and basolateral membranes of rabbit cortical collecting duct (CCD), exact cell types having V-1 receptors remain unestablished. To identify the distribution of V-1 receptor by cytoplasmic Ca2+ response, we utilized the confocal imaging system in the microperfused rabbit CCD. Basolateral application of arginine vasopressin (AVP) increased [Ca2+](i) mainly in one group of cells which were not stained by fluorescein-isothiocyanate-conjugated peanut agglutinin. Luminal application of AVP increased [Ca2+](i) in the same cells which responded to basolateral AVP. These findings provide evidence that V-1 receptors, as defined by the [Ca2+](i) response, exist in both luminal and basolateral membranes of the rabbit principal cell.