Classical protein kinase C and its hypoxic stimulus-induced translocation in the cat and rat carotid body.

Abstract

The presence, subcellular distribution, species specificity and possible hypoxic stimulus-induced translocation of classical protein kinase C (cPKC) isozymes were examined in the carotid body. Carotid bodies were dissected from cats exposed in vivo to normoxic or acute hypoxic conditions and from normoxic rats. For immunohistochemistry isoform-specific monoclonal antisera to PKCalpha, PKCbetaI, PKCbetaII and PKCgamma were used. The immunoreactivity was visualized by fluorescein isothiocyanate (FITC) labelling. FITC/Texas red double-labelled specimens for the cPKC isozymes/tyrosine hydroxylase were used to demonstrate the chemoreceptor cell localization of cPKC isozymes. The immunofluorescence was detected using laser scanning confocal image technology. The results showed expression of the PKCalpha and PKCgamma but not PKCbeta isoforms in the cytoplasm of carotid body chemoreceptor cells. The double labelling provided evidence for the chemoreceptor cell localization of the cPKC isoforms detected. The immunostaining was most intense in the periphery of the perikarya, the nuclear envelope and, occasionally, the nucleoplasm. No major differences were found in the immunolocalization of PKCalpha and PKCgamma under normoxic and hypoxic conditions or between species. However, the immunoreactivity tended to accumulate more in the peripheral cytoplasm and away from the nucleus in the hypoxic chemoreceptor cell. This study demonstrates the presence of classical protein kinase C enzymes in chemoreceptor cells. The intensity of the immunoreactivity may suggest a role for the classical protein kinase C signalling pathway in shaping the hypoxic response at the carotid body. However, this study failed to provide firm evidence of this.