On the maturation-inducing substance produced in starfish gonad by neural substance

Abstract

Maturation-inducing substance (MIS), an inducer of oocyte maturation and spawning in starfish, which is produced in the ovary under the influence of hormonal peptide (GSS) released from nervous tissue, is 1-methyladenine. Synthetic 1-ethyladenine also can induce oocyte maturation and spawning. 1-Methyladenosine, which induces oocyte maturation and spawning when applied to isolated ovarian fragments, seems to be hydrolyzed into 1-methyladenine and ribose by 1-methyladenosine ribohydrolase present in the ovarian tissue; its activity is ascribed to the resulting 1-methyladenine. The maturation-inducing activity found in 1-methyl AMP also seems to be due to its breakdown product, 1-methyladenine. Isolated follicular tissue can produce 1-methyladenine under the influence of GSS. Methionine enhances the production of MIS, whereas ethionine inhibits it, suggesting that the action of GSS in producing MIS is due to its activation of an enzyme which catalyzes methylation of the N1 site of the purine nucleus of the precursor of 1-methyladenine. 1-Methyladenine acts on the oocyte from the outside to bring about some morphological change in the oocyte surface, and also cytoplasmic maturation as revealed by fertilizability; germinal vesicle material does not contribute to these phenomena. Breakdown of the germinal vesicle does not seem to be induced by the direct action of 1-methyladenine but by a third hypothetical substance produced in the egg cortex under the influence of 1-methyladenine. Besides inducing oocyte maturation and spawning in vitro, 1-methyladenine also induces spawning behavior and, in some brooding starfish, brooding behavior when injected in vivo.