In previous work we used immunofluorescent staining with specific antibodies to study the distribution of five desmosomal antigens in the epithelia of different vertebrate animals. We showed that all five antigens were present in all epithelia studied in human, bovine, rat, guinea pig, chick and frog (Rana pipiens) tissues. It was concluded that desmosomes are highly conserved structures. This paper extends those studies: by including three other species, a lizard (Lacerta viridis), the axolotl (Ambystoma mexicanum) and the trout (Salmo trutta), and by looking at several tissues in more detail. The principal results are as follows. The epidermis of all species down to the frog stain with equal intensity for all desmosomal antigens. In the epidermis of axolotl and trout, staining for desmosomal plaque constituents is present, but staining for the desmosomal glycoproteins is greatly reduced or absent. Within mammalian species as well as chick, lizard and frog, staining for the 115 X 10(3) and 100 X 10(3) molecular weight desmosomal glycoproteins is less intense in non-epidermal tissues than in the epidermis, while staining for desmosomal plaque constituents and for the 150 X 10(3) molecular weight glycoprotein is undiminished. It is possible, therefore, that slight differences exist between certain glycoproteins of epidermis and non-epidermal epithelia. The hearts of lower vertebrates (lizard, frog, axolotl and trout) stain only for individual desmosomal plaque antigens. The pillar cells of trout gill stain, adjacent to their collagenous columns, for one desmosomal plaque antigen. There is a fibrous cytoplasmic mat in this position but no desmosomes. Thus one of the desmosomal antigens may have a function outside the desmosome.

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