Calcium transport and calcium activated ATPase activity in microsomal vesicles of rat gastric mucosa.
1. Microsomal and plasma membrane vesicles, isolated from rat gastric mucosa, were found to exhibit Ca(2+)-dependent ATPase activities of 14.1 +/- 1.4 and 7.8 +/- 1.1 mumol/mg/hr, respectively. The optimum conditions for the microsomal Ca(2+)-ATPase was pH 6-7, and required Mg2+, while divalent cation such as Cu2+, Zn2+, Fe2+, Ba2+ and Cd2+ had no significant effect. 2. As in the case of Ca2+, Mg(2+)-ATPase, the Ca2+ uptake activity of the microsomal membrane required Mg2+. Both processes were stimulated by submicro molar concentrations of Ca2+ and the apparent Km for Ca2+, Mg2+ ATPase and Ca2+ uptake activities were 0.06 microM and 0.02 microM, respectively. 3. Divalent cations Ba2+ and Fe2+, inhibited both microsomal activities, while Zn2+ and Cd2+ showed no effect on them. However, the monovalent cation K+ did not stimulate Ca2+, Mg(2+)-ATPase and Ca2+ uptake activities. 4. The Ca2+ pumping ATPase of rat gastric mucosal microsome cross-reacted with a monoclonal antibody (mAb-5F10) against the human erythrocyte Ca2+ pump. The apparent molecular weight of mucosal Ca2+ pump was 98 kDa. 5. Close relationship between the kinetic parameters of Ca2+, Mg(2+)-ATPase and Ca2+ uptake activities, and the cross reaction of 98 kDa protein of mucosal microsome with erythrocyte Ca2+ pump antibody, strongly suggest the expression of Ca2+ pump in rat gastric mucosa.
Kasinathan
C
C
Research Center, University of Medicine and Dentistry of New Jersey, Newark 07103-2400.
Sundaram
P
P
Slomiany
B L
BL
Murty
V L
VL
Slomiany
A
A
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002413:Cations, Divalent; D004789:Enzyme Activation / Q000187:drug effects; D005753:Gastric Mucosa / Q000201:enzymology* / Q000648:ultrastructure; D008081:Liposomes; D008297:Male; D008861:Microsomes / Q000201:enzymology* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley
D002413:Cations, Divalent; D008081:Liposomes; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium