The major yolk glycoprotein precursor in echinoids is secreted by coelomocytes into the coelomic plasma

The echinoid perivisceral coelomic plasma contains a prominent glycoprotein particle which has a sedimentation coefficient of 22S in Dendraster excentricus and 24S in Strongylocentrotus purpuratus. The major constituent of the plasma particles is a 200 kDa glycopeptide which is also an abundant constituent of the major yolk glycoprotein precursor particles stored in the ovarian accessory cells prior to vitellogenesis [Ozaki, H. et al.: Wilhelm Roux' Arch. Dev. Biol. 195, 74-79 (1986)]. Through in vitro culture analysis we have found that the high molecular weight plasma glycoprotein is secreted by coelomocytes of the perivisceral coelom. Moreover, the results of radioisotope labeling experiments in D. excentricus have shown that the synthesis of the high molecular weight glycoprotein took place predominantly in the coelom, and that its synthesis was not detectable in the ovary or digestive tract. It appears, therefore, that the yolk glycoprotein precursor when secreted by the coelomocytes reaches the ovary through the circulatory system.