The "coat" of kidney intercalated cell tubulovesicles does not contain clathrin.

Intercalated cells of kidney collecting ducts contain a population of tubulovesicles in their apical cytoplasm, whose limiting membranes are decorated by arrays of dense, club-shaped projections oriented toward the cytoplasm. These tubulovesicles have been implicated in endo-exocytotic events in these cells. To determine a possible relationship between this "coating" material and clathrin, the coat protein associated with endocytotic coated pits and coated vesicles in other cell types, we applied a monospecific, affinity-purified anti-clathrin antibody to thin sections of rat kidney embedded at low temperature in Lowicryl K4M. We found that no specific labeling was associated with the studlike material of intercalated cell tubulovesicles.