Tubulocisternal endoplasmic reticulum in human eccrine sweat glands

Human eccrine sweat glands, including those expressing the gene for cystic fibrosis, were stained sequentially en bloc with uranyl acetate, lead citrate and copper sulfate, and osmium tetroxide for the ultrastructural demonstration of tubulocisternal endoplasmic reticulum (TER). This organelle has been associated with water and electrolyte transport in other epithelia. TER was present in the apical cytoplasm and basolateral cytoplasm circumscribing intercellular canaliculi of clear cells in the secretory coil and in the apical cuticular cytoplasm of luminal cells in the coiled duct. In both the secretory coil and duct, TER was situated strategically around the tight junctions. Together, the TER and tight junctions may regulate the secretory and absorptive permeability of the eccrine sweat gland to NaCl and water. The dark cell of the coil which is exocrine, and the deep cell of the duct which lacked tight junctions, did not contain TER. In sweat glands obtained from three cases of cystic fibrosis, elements of TER were more prevalent and complex in luminal cells of the secretory duct than was the TER in normal sweat glands. This difference may be a consequence of the basic electrolyte abnormality of cystic fibrosis.