thromboplastin and 3-deazaadenosine

Mouse trophoblast cells are constitutive producers of the thromboplastin apoprotein in vitro. The effects on thromboplastin activity of the three transmethylation inhibitors 3-deazaadenosine (DZA), 3-deazaaristeromycin (DZAri) and erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA), the four calcium antagonists TMB-8, verapamil, nifedipine and felodipine, the prostaglandin E2 (PGE2), the phosphodiesterase inhibitor 1-methyl 3-isobutylxanthine (MIX) and monensin have been studied. No cytotoxic effects were detected when trypan blue exclusion, release of lactic dehydrogenase, incorporation of 14C-leucine into protein and cell morphology were monitored. TMB-8, felodipine, nifedipine and verapamil all abolished the increase in thromboplastin when added after 68 hr or 90-96 hr in culture. EHNA and DZAri had the same effect (but were only added at 90-96 hr). DZA had a similar effect when added at 68 hr and an even more marked inhibitory effect when added at 90-96 hr. Monensin prevented the increase in thromboplastin activity at 68 hr as well as at 90-96 hr. The combination of DZA and 1-homocysteine thiolactone (Hcy) further increased the inhibition, indicating that in these cases synthesis as well as degradation of thromboplastin were altered. The combination of DZA/Hcy and one of the four calcium antagonists gave no additional inhibitory effect. PGE2 had a biphasic dose-dependent effect. The increased thromboplastin activity at low concentrations of PGE2 (10 ng/ml) was inhibited by addition of one of the compounds verapamil, felodipine, nifedipine or DZA/Hcy. PGE2 at higher levels (10 micrograms/ml) significantly inhibited thromboplastin synthesis. Combination of PGE2 (10 micrograms/ml) and one of the calcium antagonists, DZA/Hcy or MIX gave no significant additive inhibitory effect.

Topics: 1-Methyl-3-isobutylxanthine; Adenine; Adenosine; Animals; Calcium Channel Blockers; Dinoprostone; Felodipine; Female; Gallic Acid; Methylation; Mice; Monensin; Nifedipine; Nitrendipine; Pregnancy; Prostaglandins E; Thromboplastin; Trophoblasts; Tubercidin; Verapamil

Immune complexes (IC), 12-O-tetradecanoylphorbol-13-acetate (TPA), endotoxin (LPS) and phytohaemagglutinin (PHA) induce thromboplastin activity in human peripheral blood monocytes. In the presence of transmethylation inhibitors 3-deazaadenosine (DZA) and homocysteine a dose-dependent inhibition of the thromboplastin response reaching about 60 per cent was observed, when IC, LPS or PHA was used as the stimulant. TPA-induced thromboplastin synthesis was more resistant (maximum 20 per cent inhibition).

Topics: Dose-Response Relationship, Drug; Homocysteine; Humans; In Vitro Techniques; Methylation; Monocytes; Phytohemagglutinins; Ribonucleosides; Thromboplastin; Tubercidin

Confluent monolayers of human umbilical vein endothelial cells in culture responded with a 5-fold increase in thromboplastin (tissue factor) synthesis when exposed to 12-O-tetradecanoyl-phorbol-13-acetate (TPA) (50 ng/ml) or endotoxin (ETX) (25 micrograms/ml) for 16 hr. This induced thromboplastin synthesis was markedly inhibited by exposure of the cells to two different phosphodiesterase inhibitors, methylisobutylxanthine (MIX) and rac-4(3-butoxy-4-methoxybenzyl)-2-imidazole idinone (RO-20-1724) and to the transmethylation inhibitors 3-deazaadenosine (DZA) and 1-homocysteine thiolactone (Hcy) in combination. It was slightly (TPA) or not at all (ETX) inhibited upon exposure of the cells to the intracellular calcium antagonist 8-(N,N-diethylamino)-octyl 3,4, 5-trimethoxybenzoate hydrochloride (TMB-8). However, in the presence of MIX TMB-8 had a moderate additional inhibitory effect on TPA-induced thromboplastin response. The thromboplastin response of endothelial cells in vitro thus probably depends on transmethylation events for its full expression. It is also strongly modulated by the intracellular level of cAMP.

Topics: 1-Methyl-3-isobutylxanthine; Cells, Cultured; Dose-Response Relationship, Drug; Endothelium; Endotoxins; Gallic Acid; Homocysteine; Humans; In Vitro Techniques; Tetradecanoylphorbol Acetate; Thromboplastin; Tubercidin