Effect of guanosine triphosphate on the release of Ca2+ from intracellular store sites of saponin-treated human peripheral lymphocytes.
The effects of guanosine triphosphate (GTP) on the release and uptake of Ca2+ in nonmitochondrial intracellular store sites of human peripheral lymphocytes were examined. GTP in the presence of 3% polyethylene glycol released Ca2+ from the intracellular store sites of lymphocytes in a dose-dependent manner, and the maximal release was obtained at 10 microM GTP. GDP and 5'-GMP also enhanced the release of Ca2+. On the other hand, Ca2+ uptake in the presence of oxalate by saponin-treated lymphocytes was stimulated by GTP and this stimulation was abolished when polyethylene glycol was concomitantly present. The dose dependence of the stimulated Ca2+ uptake by GTP was much the same as that of the Ca2+ released by GTP. These results indicate that GTP has an inherent activity to release Ca2+ as well as to stimulate the uptake of Ca2+ in nonmitochondrial intracellular store sites of saponin-treated lymphocytes. The stimulatory effect of polyethylene glycol on GTP-mediated Ca2+ release may occur by inhibiting functions of the Ca2+ pump.
Suematsu
E
E
Third Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Hirata
M
M
Nishimura
J
J
Koga
T
T
Ibayashi
H
H
D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D012503:Saponins / Q000494:pharmacology*
D002132:Calcium Radioisotopes; D012503:Saponins; D006160:Guanosine Triphosphate; D002118:Calcium