Lysosomal hydrolases of the epidermis. 5. Variation with depth in the cow snout

The activity of twelve acid hydrolases has been measured in serial horizontal sections of cow snout epidermis. The majority of these enzymes showed a clear peak in the basal and lower spinous cell layers; acid phosphatase, however, was found mainly in the keratinizing zone. These findings suggest that two discrete populations of lysosomes may occur in epidermis. Those present in the lower layers possess a typical pattern of hydrolase activity and probably correspond to the 'orthodox' lysosomes observed by electron microscopy techniques, whereas those found in the keratinizing zone possess an unusual hydrolase profile and may correspond to the bodies identified morphologically as keratinosomes (Odland bodies, membrane-coating granules).