Demonstration of gap junctions in frog skin epithelium.

The morphology and distribution of the intercellular junctions were investigated in isolated skin of Rana pipiens using various electron-microscopic techniques. Our evidence demonstrates the presence of gap junctions and suggests that the distribution of gap junctions is not homogeneous among the epithelial strata. Gap junctions were less frequent in the stratum corneum and stratum granulosum than in the stratum spinosum and stratum germinativum. These results support a model of widespread intercellular coupling, although the lower number of gap junctions in the stratum granulosum suggests a possible deficiency in intercellular coupling. Tight junctions were found only in two apical strata of the epithelium (stratum corneum and stratum granulosum). Desmosomes were located in all strata.