On the mechanism of action of a new pregnancy-terminating agent. Part I: Effects of prostaglandin F2 alpha metabolism in the rat and the hamster.

Studies have been carried out to evaluate the effects of 3-(2-ethyl-phenyl)-5-(3-methoxyphenyl)-1H-1,2,4 triazole (DL 111-IT) a new non-hormonal post-implantation anti-fertility agent, on metabolism of prostaglandin F2 alpha (PGF2 alpha MET) by the utero-placental unit (UPU) and the lung. In rats treated with a single (100 mg/kg) subcutaneous minimal 100%-effective dose, DL 111-IT showed a slight and transient inhibitory effect on UPU PGF2 alpha MET, whereas after multiple (2.5 mg/kg/day for 3-5 days), equally effective doses, no effect was observed. In addition, PGF2 alpha levels in both plasma and the UPU were not changed. In rat lung, PGF2 alpha MET was markedly inhibited either after single or multiple injections and the inhibition was prolonged for at least 5-6 days after administration. In hamster, on the contrary, doses up to twenty times greater than 100%-effective ones caused only a slight inhibition of PGF2 alpha MET. The effects of DL 111-IT seem therefore to be dose and species dependent, but not to be related to its pregnancy-terminating activity, thus excluding the involvement of this effect as a part of its mechanism of action.