Effect of some drugs on thromboplastin activity in mouse trophoblast cells in vitro and in vivo

Abstract

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 E 2 (PGE 2), 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. PGE 2 had a biphasic dose-dependent effect. The increased thromboplastin activity at low concentrations of PGE 2 (10 ng/ml) was inhibited by addition of one of the compounds verapamil, felodipine, nifedipine or DZA/Hcy. PGE 2 at higher levels (10 μg/ml) significantly inhibited thromboplastin synthesis. Combination of PGE 2 (10 μg/ml) and one of the calcium antagonists, DZA/Hcy or MIX gave no significant additive inhibitory effect.