ULTRACYTOCHEMICAL LOCALIZATION OF CA²⁺-ATPase ACTIVITY ON THE EPITHELIAL CELLS OF RAT TRACHEA

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A new one-step method for light and electron microscopic localization of Ca²⁺-ATPase activity was applied to the rat trachea.
Under light microscopic examination, Ca²⁺-ATPase reaction was found on the luminal side of the tracheal epithelium and on the nerve fibers of the submucosa. On electron microscopic examination, the most intense Ca²⁺-ATPase reaction was observed on the ciliated cells in the tracheal epithelium. Cytochemical reaction products were observed in the axoneme, probably corresponding to the bridge-like structures between the axoneme and ciliary membrane, the outer and inner arms of doublets, the radial spoke heads, the central sheath, the central core bridge, and the outer surface of the ciliary membrane. Enzyme activities were also found on the peripheral structures of triplets, which may correspond to connectors, and fibrous elements of the rootlet bundle. The reaction completely disappeared when Ca²⁺ or ATP was removed from the incubation medium. Substrate specificity was observed by substituting NPP or GP for ATP in the incubation medium. Lead and phosphate were identified in the reaction product by X-ray microanalysis with an analytical electron microscope, suggesting that the reaction products were lead phosphate. Ca²⁺-ATPase reaction was also observed on the microvilli, lateral plasma membrane, and cytoplasmic projections in both ciliated and non-ciliated cells such as brush cells, secretory cells, intermediate cells, and basal cells.
From these results, it was concluded that Ca²⁺-ATPase activities, considered to be related to ciliary movement and Ca²⁺-transport, have been clearly localized in the rat trachea.