Use of Intrauterine Microdialysis to Investigate Methanol-Induced Alterations in Uteroplacental Blood Flow

Methanol is teratogenic in rodents; it has been postulated that this teratogenicity may be mediated in part by conceptal hypoxia. To construct a model to predict conceptal risk following maternal methanol exposure, conceptal disposition of methanol must be determined and any effects of such exposure on blood flow must be quantitated. In the present study, these toxicokinetic and toxicodynamic parameters were evaluated byin vivointrauterine microdialysis. Microdialysis probes were inserted into the uteri of Gestational Day (gd) 20 rats; methanol was administered as either an iv bolus (100 or 500 mg/kg) or infusion (100 or 1000 mg/kg/hr). In separate experiments, methanol (100 or 500 mg/kg) and³H₂O (20 μCi/kg) were administered iv to gd 20 and 14 rats and gd 18 mice. In both experiments, maternal blood and uterine microdialysate were collected and analyzed for methanol or³H₂O content. The methanol concentration–time data were consistent with saturable maternal elimination and apparent first-order transfer between maternal and conceptal compartments; at distribution equilibrium, conceptal methanol concentrations exceeded those in the dam by approximately 25%. The initial rate of conceptal permeation of methanol was proportional to the reciprocal of maternal blood methanol concentration (r²= 0.910). Methanol also reduced significantly the rate of³H₂O uptake into the conceptus in a concentration-dependent fashion in gd 14 and 20 rats and gd 18 mice. These data indicate that methanol may decrease uteroplacental blood flow, decreasing methanol presentation to the conceptus and possibly producing conceptal hypoxia.