A Convenient Procedure for the Detection of Inhibitors of Macromolecule Biosynthesis Using Oocytes and Embryos of Echinoderms Inhibition of Protein Synthesis by Pentopyra nine C

Abstract

In early sea urchin embryos, maternal messenger RNA synthesized during oogenesis plays a central role in translation. Protein synthesis occurs in the presence of inhibitors of RNA synthesis such as actinomycin D. The cleavage divisions require protein and DNA synthesis. On the other hand, starfish oocytes undergo meiotic maturational divisions in the presence of inhibitors of RNA and DNA synthesis. The maturational process is prevented by inhibitors of protein synthesis. Therefore, one can distinguish between inhibitors of RNA synthesis and those of protein synthesis by using sea urchin embryos and starfish oocytes.
Effects of pentopyranine C, i. e.1α-(3'-deoxy-L-arabinopyranosyl) cytosine were examined on mitotic divisions of sea urchin embryos and on meiotic maturational divisions of starfish oocytes. The only known action of pentopyranine C is to suppress the uridine incorporation into RNA in Ehrlich ascites cells. It was revealed that both cell divisions were susceptible to the drug application. Biochemical analyses using labeled nucleosideshave shown that pento- pyranine C dose not inhibit the biosynthesis of nucleic acids in sea urchin embryos although incorporation of the nucleosides into the cells is suppressed. Pentopyranine C inhibited protein synthesis in fertilized sea urchin eggs that had been preloaded with a labeled amino acid. Thus, the bioassay method as proposed in this study has been shown to be efficient in disting- uishing between inhibitors of RNA synthesis and those of protein synthesis.