THE CONCENTRATIONS OF ACSDKP, A PHYSIOLOGICAL INHIBITOR OF CELL-PROLIFERATION, VARY DURING OOGENESIS AND EARLY DEVELOPMENT IN XENOPUS-LAEVIS

The endogenous tetrapeptide AcSer-Asp-Lys-Pro (AcSDKP) is present in t he circulation and cells of mammals. Extracellular AcSDKP is a negativ e regulator of cell proliferation inhibiting the S phase entry of nume rous cell types such as hematopoietic progenitors, hepatocytes, lympho cytes and several continuous cell lines. In contrast, the biological r ole of cellular AcSDKP remains unknown. We have recently reported a de crease of cellular AcSDKP concentrations by 50% accompanying the initi ation of DNA synthesis in mitogen-induced proliferation of human lymph ocytes. In the present study we measured the variations of cellular Ac SDKP concentrations during oogenesis and early development of Xenopus. Cellular AcSDKP concentrations peaked at stage IV of oogenesis and th en continuously decreased during the final oocyte maturation and durin g the initial 15-h period of exponential cell division of the embryo. Altogether, our present and previously published data suggest that cel lular AcSDKP may be involved in the regulation of cell proliferation i n eukaryotic species.