On the mechanism of action of a new pregnancy-terminating agent. Part I: Effects on prostaglandin F2α 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 nonhormonal post-implantation anti-fertility agent, on metabolism of prostaglandin F2α (PGF2α 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 PGF2α MET, whereas after multiple (2.5 mg/kg/ day for 3–5 days), equally effective doses, no effect was observed. In addition, PGF2α levels in both plasma and the UPU were not changed. In rat lung, PGF2α 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 PGF2α MET. The effects of DL 111-IT seem therefore to be dose and species dependent, but not to be related to its pregnancyterminating activity, thus excluding the involvement of this effect as a part of its mechanism of action.