Immunelectron microscopic localization of cathepsin B in human exocrine glands.

The distribution of the lysosomal enzymes cathepsin B, lysozyme, chymotrypsin, and neutrophil elastase was examined in eccrine, apocrine, and sebaceous glands using a postembedding immunogold labeling procedure. Various amounts of cathepsin B were detected in all glands. Lysozyme, however, was detected in apocrine glands only. The other two lysosomal enzymes were not detectable immunologically. In apocrine and eccrine glands, anti-cathepsin B antibody labeled all secretory granules. In sebaceous glands, only the peripheral layer of cells showed immunological activity for cathepsin B. In apocrine glands, granules containing remnants of cristae were more intensively labeled than those lacking cristae which supports the assumption that both granules are derived from mitochondria by acquiring lysosomal enzymes. The enzymes convert mitochondria to granules with cristae and finally to granules without cristae. Thus the difference in morphology is part of a spectrum of the degradation of mitochondria to granules.