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The effects of inhibitors of RNA synthesis (α‐amanitin and actinomycin D) on preimplantation mouse embryogenesis

1973; Wiley; Volume: 186; Issue: 2 Linguagem: Inglês

10.1002/jez.1401860211

1097-010X

Mitchell S. Golbus, Patricia G. Calarco, Charles J. Epstein,

Reproductive Biology and Fertility

Abstract Actinomycin D and α‐amanitin (an inhibitor of RNA polymerase II) were used to determine the effect of inhibiting RNA synthesis during pre‐implantation mouse embryogenesis. Actinomycin D (0.01 μg/ml) was an effective inhibitor of blastulation and of cleavage from the 1 cell stage on. The first cleavage of day 0 (1 cell) embryos cultured for 24 hours in α‐amanitin (10 −7 to 10 −5 M) was reduced to 35‐42% from a control value of 60%. Cleavage of day 1 (2 cell) embryos and day 2 (8–12 cell) embryos was only modestly inhibited during the first 24 hours of culture in α‐amanitin, but development beyond that point was seriously impaired. Day 3 morulae were inhibited from blastu‐lating although the degree of inhibition was not dose related. Electron microscopy of embryos cultured in α‐amanitin revealed predominantly nucleolar changes. No difference in the activities of hypoxanthine‐guanine phosphoribosyltrans‐ferase (HGPRT) and guanine deaminase were found in morulae developed from the 4 cell or later stages in control medium or medium containing 10 −5 M α‐amanitin, despite an 87% inhibition of leucine incorporation into protein. Neither the normal rise in HGPRT activity nor the normal fall in guanine deaminase activity occurred in the morulae developed from the 2 cell stage in the presence of α‐amanitin, even though both α‐amanitin treated and control embryos had the same number of blastomeres. It is suggested that RNA synthesis is necessary throughout the mouse pre‐implantation period, including the 1 cell stage.