DIFFERENTIAL EXPRESSION OF PKC ISOFORMS IN FRESH AND CULTURED RABBIT CCD

Growth of rabbit cortical collecting duct (CCD) cells in primary cultu re results in a phenotype in which there is a stable stimulation of Na + transport by arginine vasopressin. Our objective was to determine wh ether this altered phenotype was associated with altered expression of protein kinase C (PKC) isoforms. Western blot analysis of extracted p roteins and reverse transcription-polymerase chain reaction analysis o f extracted RNA showed expression of PKC-alpha, -epsilon, and -zeta in microdissected CCD segments and in fresh and cultured immunodissected CCD cells. These techniques also suggested that the rabbit CCD expres ses PKC-eta- and -theta-like isoforms, which have not been identified in this species. Growth of CCD cells in primary culture produced no ap parent change in the level of expression of PKC-alpha, -epsilon, or -z eta; however, the theta-like isoform was strongly expressed in fresh C CDs but only weakly expressed in cultured CCDs. The putative eta-isofo rm was more heavily expressed in cultured than in fresh CCD cells. The consequences of altered expression of these two isoforms in fresh and cultured rabbit CCD remain unknown, but the possibility exists that t hey are involved in the altered arginine vasopressin response of cultu red cells.