engleski

Absence of vacuolar H+-ATPase from rat small intestine brush-border membranes

Experiments were performed to establish whether rat small intestinal brush-border membranes (BBM) contain a vacuolar (V)-type, bafilomycin-sensitive H+-ATPase involved in the maintenance of the acid microclimate. This ATPase should be localized at the inside of BBM vesicles and be accessible for ATP only in the presence of a detergent. Increasing concentrations of Triton X-100 did not disclose a bafilomycin-sensitive H+-ATPase activity in the intestinal BBM vesicles. Likewise, a number of other detergents that in renal BBM vesicles revealed the H+-ATPase failed to expose a similar ATPase activity in vesicles from the small intestine. In western blot and immunohistochemical studies, specific antibodies against the 31 kDa and 70 kDa H+-ATPase subunits clearly labeled respective antigens in BBM of the kidney whereas in BBM of the small intestinal eneterocytes these subunits were not detected. The results demonstrate that a V-type H+-ATPase is not present in the BBM of enterocytes and, hence, cannot contribute to the maintenance of the acid microclimate.

vacuolar H+-ATPase; brush-border membrane; small intestine; rat

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