IMMUNOLOCALIZATION OF PHOSPHOLIPASE-C ISOFORMS IN RAT-KIDNEY

Background. Phospholipase C (PLC) is an important factor in signal tra nsduction because this enzyme is activated by several hormones and gro wth factors. Eight PLC isoforms have been described raising the possib ility that different cells express a single isoform or activate specif ic isoforms in different cells. Therefore, the goal of this study was to determine which PLC isoforms are expressed in specific regions of r at kidney. Methods. Western blot analysis was performed in microdissec ted nephron segments of rat kidney, while immunohistochemical analysis was performed on whole rat kidney slices using PLC isoform-specific a ntibodies. Results. All three families of PLC isoforms (beta, gamma, a nd delta) were present throughout the cortical and medullary regions o f the kidney. Only the PLC-beta 1 isoform was observed in the brush bo rder of the proximal tubule, but all isoforms were present in glomerul i and in the cytoplasm of tubular epithelial cells. In addition, only the PLC-gamma 1 isoform was expressed in the internal elastic lamina o f the renal artery, while vasa recta expressed PLC-beta 1 most intense ly. Medullary thick ascending limbs showed an intense level of express ion of all three isoforms. Conclusion. Multiple PLC isoforms are prese nt in glomeruli, renal tubules. and renal vasculature in vivo, but wit h some segment-specific differences. These findings suggest that the r esponse of a specific cell is not determined by expression of only one PLC isoform, with the exception of the brush border of the proximal t ubule and the renal arteries. Instead, the presence of multiple PLC is oforms in specific regions of the kidney suggests that hormonal regula tion in vivo involves mechanisms beyond cell-specific isoforms of PLC.