Phosphatidylinositol liposomes increase calcium uptake and tissue plasminogen activator secretion by fetal human lung fibroblasts.
PtdIns liposomes, at a concentration of 40 microM, induced in FLF the synthesis of t-PA-Ag, and enhanced 45Ca2+ uptake. The induction of t-PA-Ag biosynthesis by PtdIns liposomes in FLF was inhibited by 5-15 microM verapamil, an inhibitor of Ca2+ uptake via the so-called "slow channels" by 0.5-10 microM TFP, an inhibitor of Ca2+ transport ATPase, and by 10-90 microM TMB-8, an inhibitor of intracellular Ca2+ mobilization. t-PA-Ag secretion was inhibited by decreasing the Ca2+ concentration less than 1.2 mM. On the other hand, addition of 0.08 microM of calcium ionophore A23187 increased t-PA-Ag biosynthesis after 72 hr of incubation by 247% (P less than 0.01). These data support previous results and indicate that the synthesis of t-PA in FLF is Ca2+ dependent. Thus, it is suggested that PtdIns liposomes increase t-PA biosynthesis by affecting calcium metabolism.
Maran
R
R
Department of Biophysics, Weizmann Institute of Science, Rehovot, Israel.
Kadouri
A
A
Floru
S
S
Gelvan
A
A
Cohen
A M
AM
D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002478:Cells, Cultured; D005333:Fetus; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008081:Liposomes / Q000494:pharmacology*; D008168:Lung; D010716:Phosphatidylinositols / Q000494:pharmacology*; D010959:Tissue Plasminogen Activator / Q000096:biosynthesis*
D002121:Calcium Channel Blockers; D008081:Liposomes; D010716:Phosphatidylinositols; D000001:Calcimycin; D010959:Tissue Plasminogen Activator; D002118:Calcium