Cytokeratin localization in toe pads of the anuran amphibian Philautus annandalii (Boulenger, 1906).

We have examined cytokeratin distribution and their nature in toe pads of the Himalayan tree-frog Philautus annandalii. Toe pads are expanded tips of digits and show modifications of their ventral epidermis for adhesion. The toe pad epidermal cells, being organized into 3-4 rows, possess keratin bundles, especially in surface nanostructures that are involved in adhesion. Immunohistochemical localization using a pan-cytokeratin antibody revealed that cytokeratin immunoreactivity is the strongest in the mid- to basal cell rows of the epidermis, which parallels our previous ultrastructural observation of dense keratin bundles present in this part of the epidermis. The remainder of the epidermis (i.e., the superficial cell layer) showed little immunoreactivity. Immunoblot analysis revealed that toe-pads possessed keratins prominently in the molecular mass of 50 kDa. Possible presence of keratin 5 in toe pad epidermis has been correlated with its usual distribution pattern in mammalian epidermis.