Characteristics of the isolated apical plasmalemma and intracellular tubulovesicles of the gastric acid secreting cells: demonstration of secretagogue-induced membrane mobilization.
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.
Ray
T K
TK
Department of Surgery, SUNY Health Science Center, Syracuse 13210.
Das
P K
PK
Nandi
J
J
Banerjee
A
A
Bandopadhyay
S
S
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000502:physiology; D002458:Cell Fractionation; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure*; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D005744:Gastric Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000502:physiology / Q000648:ultrastructure*; D005768:Gastrointestinal Hormones / Q000502:physiology; D017506:H(+)-K(+)-Exchanging ATPase; D006632:Histamine / Q000494:pharmacology; D008563:Membrane Lipids / Q000032:analysis; D008861:Microsomes / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure*; D011817:Rabbits; D013552:Swine
D005768:Gastrointestinal Hormones; D008563:Membrane Lipids; C052257:hydrogen potassium ATPase, gastric endogenous activator protein, mammal; D006632:Histamine; D000251:Adenosine Triphosphatases; D017506:H(+)-K(+)-Exchanging ATPase; D002118:Calcium