Localization of protein kinase C (PKC) isoenzymes α, βI, βII, δ, and ε was studied employing Western blot analysis and immunohistochemical methods including confocal laser-scanning microscopy in the kidney of two mice strains, namely, C57BL/6 and 129/Sv, which have recently been used as genetic backgrounds for respective knockout mice. Immunoblot analysis identified immunoreactive bands for each isoenzyme in total kidney cell extracts. Isoenzyme expression sites were identical for both strains. Glomeruli expressed PKC-α, -βI, and -ε. The latter isoenzme was also detected in apical aspects of proximal convoluted but not in proximal straight tubules. In contrast to rats, neither PKC-α nor PKC-βI was detectable in the proximal tubule. Immunofluorescence was observed in luminal membranes of medullary (MTAL) and cortical thick ascending limbs for PKC-βI and in MTAL for PKC-ε. The cortical collecting duct expressed PKC-α, -βI, and -δ in intercalated cells only. In the outer medullary collecting duct, PKC-α and -βI were detectable in principal cells, whereas PKC-δ was found in intercalated cells. In the inner medullary collecting duct, PKC-α, -βI, and -βII were detected. As described for the rat, the expression of PKC-βII was otherwise restricted to cortical and medullary interstitial cells. The specificity of all labeling was confirmed in respective PKC isoenzyme knockout mice. In summary, distinct expression patterns were shown for PKC isoenzymes α, βI, βII, δ, and ε in the mouse kidney.
Angiotensin II Stimulates Renin in Inner Medullary Collecting Duct Cells via Protein Kinase C and Independent of Epithelial Sodium Channel and Mineralocorticoid Receptor Activity
