title: Effects on mouse blastocysts of in vitro exposure to methylnitrosourea and 3-methylcholanthrene.
abstract: Mouse blastocysts were exposed in vitro to various concentrations of N-methyl-N-nitrosourea and 3-methylcholanthrene. The incorporation of [3H]thymidine, [3H]uridine, and [3H]leucine into the exposed blastocysts was determined either immediately following exposure or after 18 hr of culture. The concentrations of N-methyl-N-nitrosourea or 3-methylcholanthrene used had no effect on blastocyst viability in either situation. There was a concentration-dependent decrease in the incorporation of the precursors into blastocysts exposed to N-methyl-N-nitrosourea which appears to be more pronounced after 18 hr in culture. This effect was not demonstrated for 3-methylcholanthrene, which requires metabolic activation for reactivity. Blastocysts exposed to N-methyl-N-nitrosourea were injected into the uterine horns of surrogate mothers; a significant increase in the resorption rate of these blastocysts was seen when compared with controls. Similar experiments were performed to determine birth rate. A dose-dependent decrease in birth rate was observed which correlated well with the effects on incorporation of thymidine, uridine, and leucine but not with the effect of implantation rate.
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000187:drug effects* / Q000378:metabolism; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D008748:Methylcholanthrene / Q000494:pharmacology*; D008770:Methylnitrosourea / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009607:Nitrosourea Compounds / Q000494:pharmacology*; D014176:Protein Biosynthesis; D012313:RNA / Q000096:biosynthesis; D013997:Time Factors
chemical_list: D009607:Nitrosourea Compounds; D008748:Methylcholanthrene; D012313:RNA; D008770:Methylnitrosourea; D004247:DNA