Journal of Cell Science, Vol 3, 17-32, Copyright © 1968 by Company of Biologists

Submitted on July 20, 1967

Fine-Structural Localization of Adenosine Triphosphatase in the Rectum of Calliphora

¹ Department of Biology, University of Virginia Charlottesville, Virginia, U.S.A.; Department of Biology, Western Reserve University, Cleveland, Ohio 44106, U.S.A.
² Department of Biology, University of Virginia Charlottesville, Virginia, U.S.A.; Zoological Laboratory, Downing Street, Cambridge, England

Adenosine triphosphatase (ATPase) activity in the rectal papillae of Calliphora has been studied by biochemical and histochemical techniques. The microsomal fraction contained a Mg²⁺-activated ATPase with a pH optimum of 8.0. The enzyme was not stimulated by the addition of Na⁺ plus K⁺ and was insensitive to ouabain. Histochemical studies using modifications of the Wachstein-Meisel method showed that at pH 7.2 this Mg²⁺-activated ATPase was specifically localized on the intracellular surface of the lateral plasma membranes. A similar though less intense reaction was obtained with adenosine diphosphate and inosine triphosphate, but not with guanosine triphosphate, uridine triphosphate or -glycerophosphate as substrates. At an acid pH (6.6-6.8), very little reaction occurred on the lateral plasma membrane but some reaction product was present in mitochondria and nuclei. Very little enzyme activity was found in the flattened rectal epithelium. These results are discussed in relation to the available data on transport ATPases and on the structural basis of fluid transport by rectal papillae. It is proposed that the ATPase localized on the stacks of lateral plasma membrane may be involved with ion secretion into the intercellular spaces to create the osmotic gradient necessary to extract water from the lumen.