Characteristics of the isolated apical plasmalemma and intracellular tubulovesicles of the gastric acid secreting cells: demonstration of secretagogue-induced membrane mobilization

• Published in: Biochemistry (Easton) 1988-12, Vol.27 (25), p.8958-8968
• Main Authors: Ray, Tushar K, Das, Pratap K, Nandi, Jyotirmoy, Banerjee, Atreyee, Bandopadhyay, Sandip
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - metabolism; Animals; Biological and medical sciences; Calcium - physiology; Cell Fractionation; Cell Membrane - drug effects; Cell Membrane - ultrastructure; Cell membranes. Ionic channels. Membrane pores; Cell structures and functions; Centrifugation, Density Gradient; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Gastric Acid - metabolism; Gastric Mucosa - physiology; Gastric Mucosa - ultrastructure; Gastrointestinal Hormones - physiology; H(+)-K(+)-Exchanging ATPase; Histamine - pharmacology; Membrane Lipids - analysis; Microsomes - drug effects; Microsomes - physiology; Microsomes - ultrastructure; Molecular and cellular biology; Rabbits; Swine
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00425a013

Separation of the gradient-purified gastric microsome into two membrane subfractions of distinct enzymatic and phospholipid composition has been achieved by mild SDS (0.033% w/v) treatment followed by sucrose gradient centrifugation of the pig and rabbit gastric microsomes. While the high-density membranes had all of the (H+,K+)-ATPase and K+-pNPPase activities and revealed a single major 100-kDa band on SDS-PAGE, the low-density membranes contained all of the 5'-nucleotidase and nearly all of the Mg2+-ATPase. In the present study, the low-density subfraction has been characterized to be derived from the apical membranes and the high-density one from the intracellular tubulovesicular membranes of the parietal cells. Such characterization was based primarily on sole dependency of the apical plasma membranes on the endogenous activator for (H+,K+)-ATPase activity, differential sensitivity of the activator (AF)-dependent and -independent (H+,K+)-ATPase on micromolar vanadate and Ca2+, specific vitamin B12 binding ability of the apical plasmalemma, phospholipid and protein profiles of the two membrane subfractions, and other parameters. The AF, mentioned previously, has recently been implicated as a cytosolic regulator of the gastric (H+,K+)-ATPase [Bandopadhyay et al. (1987) J. Biol. Chem. 262, 5664-5670]. Two different forms (i.e., AF-dependent and -independent forms) of the (H+,K+)-ATPase are suggested to be present in the tubulovesicles on the basis of differential vanadate sensitivity while the AF-dependent form alone is present in the apical membranes. The data have been discussed in terms of stimulation-induced membrane transformation characteristic of the H+-secreting epithelia including the acid-secreting cells of the stomach.