The action of various agents was investigated on 6-day-old rabbit blastocysts in vivo and in vitro. The blastocysts were examined by the flat-mount technique. The substances studied included antimetabolites (2-deoxyglucose, 2-deoxyglucose-6-phosphate, 2-deoxygalactose, 6-mercaptopurine and 6-mercaptopurine riboside, ethionine, isoniazid, analogues of vitamin B12), enzyme inhibitors (dl-glyceraldehyde, salicylate, bromoacetylcarnitine, p-chloromercuribenzoate, fluoride), antimitotic agents (colcemid, aminopterin), cytostatic agents (actinomycin D, cytochalasin B), metabolites (DNA, glucose-6-phosphate, 2-deoxyribose, galactose), and hormones (polyoestriol phosphate, growth hormone). The influence of anoxia was also investigated, with special reference to temperature.
Agents which, under the experimental conditions laid down in this study, exerted clearly recognizable effects in vivo and in vitro, were 2-deoxyglucose, 6-mercaptopurine riboside, colcemid, isoniazid, aminopterin and DNA. Agents that were found to act in vitro only, were 2-deoxygalactose, glyceraldehyde, salicylate, bromoacetylcarnitine, 2-deoxyglucose-6-phosphate, actinomycin D, cytochalasin B, p-chloromercuribenzoate, and anoxia. An agent inert in vitro, but conducive (with longer exposure) to embryonic death in vivo, was polyoestriol phosphate. Growth hormone too, was inactive in vitro, but produced a slight effect in vivo. No effect was demonstrable in rabbit blastocysts following treatment with ethionine, analogues of vitamin B12, fluoride, glucose-6-phosphate, 2-deoxyribose, galactose.
Blastocysts, obtained from rabbits that had been subjected to embryotoxic agents (2-deoxyglucose, colcemid), were capable of recovery and further growth in vitro when the damage incurred in vivo was of a minor to moderate degree. Blastocysts moderately damaged by maternal 6-mercaptopurine or 6-mercaptopurine riboside treatment did not recover significantly; however, blastocysts more severely affected by these two compounds in vivo deteriorated further after incubation in vitro. Pretreatment of rabbits with polyoestriol phosphate yielded blastocysts which developed subsequently in vitro particularly well.
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