Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dual localization of acid phosphatase in lysosomal and extralysosomal sites of the tubule epithelial cells of normal mouse kidney was observed at the light and electron microscope level using a modified Gomori lead-salt method with p-nitrophenylphosphate (pNPP) as substrate. Based on previous biochemical and cytochemical findings, we developed optimal conditions for the enzyme activity in extralysosomal sites. The conditions used for the light microscopic level consisted of 1.5 mM PNPP, 2.0 MM Pb(NO3)2 and 0.05 M acetate buffer (pH 5.8). Those for the electron microscopic study required 3.0 mM PNPP, 3.6 MM Pb(NO3)2 and 0.1 M acetate buffer (pH 5.8). This modified lead-salt technique was highly specific and provided a suitable method for the demonstration of nonlysosomal as well as lysosomal sites of acid phosphatase activity in the tubule epithelial cells of normal mouse kidney. As expected, the enzyme activity appeared in the lysosomes, but the prominent reaction in the brush border, the rough endoplasmic reticulum and basal infolding plasma membranes was not anticipated. We were able to demonstrate in situ organelle precursors of microsomal acid phosphatase such as endoplasmic reticulum, plasma membrane and basal infolding membranes showing the same substrate preference, which had been observed previously in biochemical studies in our laboratory. Since the possible participation of alkaline phosphatases, K+-pNPPase or Na+-K+-adenosine triphosphatase was ruled out by use of appropriate inhibitors, the enzyme-reactive sites can be interpreted as reflecting nonspecific acid phosphatase.
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PMID:Demonstration of lysosomal and extralysosomal sites for acid phosphatase in mouse kidney tubule cells with p-nitrophenylphosphate lead-salt technique. 23 53

Nervous or hormonal stimulation of salivary secretion in vivo is associated with a pronounced efflux of K+ from the secretory, acinar cells into the blood. This K+ efflux is followed in the post-stimulus period by a reuptake of K+ into the glandular tissue. In the present study we monitor the changes in [K+] of physiological solutions perfusing a flow chamber containing isolated segments of mouse submandibular glands. Nervous stimulation or the application of exogenous acetylcholine (ACh, 10(-5) M) to the isolated glandular tissue results in characteristic changes in the [K+] of the superfusate, indicating net K+ release followed by K+ reuptake. The post-stimulus reuptake of K+ is shown to be susceptible to blockade by either ouabain (10(-3) M) or piretanide (10(-4) M). The reuptake was markedly attenuated if Cl- in the superfusate was replaced by either NO3- or SO4(2-). The K+ uptake was, however, unaffected when Br- replaced Cl- in the superfusate. Similar effects were observed in the unstimulated glandular tissues. The introduction of Cl-(-)free media containing either NO3- or SO4(2-) resulted in a loss of K+ from the tissue which was followed, upon reintroduction of Cl-, by a pronounced uptake of K+. When Br- was substituted for Cl- there was very little change in [K+] upon removal or reintroduction of Cl-. The uptake of K+ induced by reintroduction of Cl- after a period of NO3- or SO4(2-) superfusion was blocked by both ouabain and piretanide. This uptake of K+ was also dependent on the presence of extracellular Na+. Both Cl- and Na+ had to be present in the superfusing medium for K+ uptake to be fully manifest. These findings indicate that the K+ uptake observed in both the resting and stimulated submandibular gland cannot be explained as solely due to the activity of the Na+-K+-adenosine triphosphatase (Na+-K+-ATPase). The demonstrated anionic selectivity, dependence on extracellular Na+ and susceptibility to blockade by the diuretic piretanide would strongly suggest that a coupled Na+-K+-Cl- co-transport system operates in submandibular glands as it does in other transporting epithelia to achieve K+ uptake.
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PMID:Potassium uptake in the mouse submandibular gland is dependent on chloride and sodium and abolished by piretanide. 379 14

The responses of the cytosolic pH of hepatocytes in suspension to agents affecting the activity of vacuolar adenosine triphosphatase (V-ATPase) and Na/H exchange have been studied. Changes of cytosolic pH were determined both with dual-wavelength excitation (500/440 nm) of the fluorescence of 2',7'-bis-(2-carboxyethyl)-5(and 6)-carboxyfluorescein and from the distribution of 14C-dimethyloxazolidinedione; both methods gave very similar results. Changes of vesicular pH were determined by comparing the fluorescence of fluorescein isothiocyanate-dextran and rhodamine B isothiocyanate-dextran taken up by endocytosis. Nitrate, which inhibits V-ATPase in isolated organelles, induced a concentration-dependent acidification of the cytosol and alkalinization of vesicles, with maximal effects at 25-37.5 mM in each case, indicating that V-ATPase contributes to removal of cytosolic protons. On continued exposure to nitrate, the acidification underwent an amiloride-inhibitable reversal. At the higher concentrations of NO3-, both cytosolic acidification and vesicular alkalinization were reduced or absent. Bafilomycin A1 caused alkalinization of vesicular pH; cytosolic acidification was not observed, possibly because of other ionic exchanges. Recovery of cytosolic pH from an acid load (2 min exposure to 5% CO2) was sensitive to both 25 mM NO3- and to ouabain. The pH dependence of the nitrate effect was tested with media of different pH; the activity was negligible at cytosolic pH 6.2 and rose to a maximum at cytosolic pH 7.3. Treatment of hepatocytes with 0.5-1.0 mM ouabain resulted in an initial alkalinization (0.5-2 min duration) of the cytosol, followed by a spontaneous reversal and, on occasion, further acidification. The alkalinization was blocked by 25 mM NO3-, but not by 25 mM gluconate. The results suggest that the cytosolic alkalinization is caused by a stimulation of H+ uptake by V-ATPase activity. We conclude that V-ATPase make an important contribution to the regulation of the cytosolic pH of hepatocytes.
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PMID:Role of vacuolar adenosine triphosphatase in the regulation of cytosolic pH in hepatocytes. 770 51