METABOLIC ENZYMES IN CELOMIC CELLS (ELEOCYTES) OF THE POLYCHAETE NEREIS-VIRENS - SEX-SPECIFIC CHANGES DURING SEXUAL-MATURATION

The activities of some enzymes of the intermediary metabolism and the content of soluble protein and carbohydrate (glycogen plus free glucos e) were measured in one type of coelomic cells (eleocytes) of the poly chaete Nereis virens. Specimens used in this study were collected betw een 1989 and 1991 in Oosterscheldt Bay, The Netherlands, and divided i nto six different stages of sexual maturation as determined by the mea n oocyte volume. In both sexes, the soluble protein content in eleocyt es of immature individuals (11 mg ml-1 cell vol) increased three-fold. In prespawning N. virens the soluble protein content decreased to les s than 2 mg protein ml cell vol in females but not in males. In both s exes, the carbohydrate content decreased continuously from immature [3 00 mumol glucose equivalent (equiv) ml-1 cell vol] to prespawning indi viduals (<40 mumol glucose equiv ml-1 cell vol). During the time cours e of maturation, the specific activities (expressed as units mg-1 prot ein) of pyruvate kinase, phosphoenolpyruvate carboxykinase, malate deh ydrogenase, alanine aminotransferase and glutamate dehydrogenase decre ased in both sexes. A transient increase in the specific activities wa s found for glycogen phosphorylase and aspartate aminotransferase. No major changes were found for hexokinase, lactate dehydrogenase, glucos e-6-phosphate dehydrogenase and malic enzyme. Sex specific differences were found for the activities of citrate synthase and isocitrate dehy drogenase, which were higher in males. The specific activities of the latter enzyme increased more than ten-fold in males, but only four-fol d in female eleocytes during maturation. In eleocytes of prespawning f emales, the activities of most enzymes showed extremely high variation s not found in prespawning males. For two enzymes of fatty acid catabo lism, beta-hydroxyacyl-CoA dehydrogenase and beta-hydroxybutyrate dehy drogenase, only traces of activities were detected, suggesting the abs ence of significant fatty acid catabolism in the eleocytes. Compared t o the eleocytes, the body wall tissue showed ten-fold higher activitie s of phosphofructokinase, whereas the eleocytes displayed higher activ ities of the amino acid interconverting enzymes glutamate dehydrogenas e and alanine aminotransferase and the glyconeogenic enzyme phosphoeno lpyruvate carboxykinase. Citrate synthase activities were similar for both tissues. In the coelomic fluid of N. virens, glucose (< 0.1 to 3. 5 mM) and D-lactate (0.1 to 4 mM) were present and represent exogenous substrates for the eleocyte metabolism.