DIFFERENCES IN TYROSINE PHOSPHORYLATION OF OOCYTE KEY PROTEINS DURING5HT-INDUCED MEIOSIS REINITIATION IN 2 BIVALVE SPECIES

The neurohormone serotonin (5HT) triggers meiosis reinitiation in oocy tes of the pelecypod molluscs Spisula solidissima and Ruditapes philip pinarum. However, while Spisula oocytes complete maturation, Ruditapes oocytes arrest in metaphase I. Anti-phosphotyrosine antibody revealed that serotonin triggered an early tyrosine phosphorylation of p42(map k) which was transient in Spisula, but persisted in Ruditapes. Moreove r, dephosphorylation of tyrosine residues of p34(cdc2) was only observ ed in Spisula oocytes, simultaneously with germinal vesicle breakdown. The possibility is discussed that such differences may account for ma intenance of the metaphase I block. (C) 1994 Academic Press, Inc.