HORMONAL CONTROL OF OOCYTE MATURATION IN ARENICOLA MARINA L. (ANNELIDA, POLYCHAETA). III. INVOLVEMENT OF CA2+ AND -SH GROUPS IN MEIOSIS REINITIATION

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Abstract
In A. marina (Annelida, Polychaeta) the oocytes are arrested in the 1st prophase stage of meiosis until spawning. Oocyte maturation is under hormonal control; when incubated in vitro in a brain extract oocytes reach the 1st metaphase at which they remain arrested until fertilization. The importance of Ca in oocyte maturation was investigated by using different drugs known to act on membrane Ca permeability and to modify intracellular free Ca concentration. Tetracaine, procaine, D-600 [.alpha.-isopropyl-.alpha.[N-methyl-N-homoveratryl-.gamma.-aminopropyl]-3,4,5-trimethoxyphenyl-acetonitrile], verapamil (Isoptin), propranolol, oxprenolol and lanthanum chloride, Ca deprivation but not ionophore A23187, are all able to induce oocyte maturation. The brain hormone may act on the oocyte by regulating, probably increasing, the intracellular free Ca concentration. The importance of -SH/-SS- in meiosis reinitiation is suggested by the fact that dithiothreitol and 2,3-dimercaptopropanol, 2 disulfide reducing agents, both induce oocyte maturation.