Subcellular distribution of [ 3H]serotonin binding sites in blastula, gastrula, prism and pluteus sea urchin embryos

Abstract

1. The presence and intracellular location of serotonin binding sites in embryos of the sea urchin, Arbacia punctulata, were investigated by the binding of radiolabelled serotonin to late blastulae, gastrulae, prism larvae, early pluteus larvae, and advanced pluteus larvae subcellular fractions. 2. Although [ 3H]serotonin binding activity was demonstrated in some cell fractions from each developmental stage examined, the subcellular distribution of binding sites was stage-specific. 3. In the older plutei, serotonin binding sites were tentatively determined to be located on cell surface membranes. 4. In younger embryos the localization of serotonin binding sites to other cell organelles is suggested. 5. [ 3H]serotonin bound to nuclei of late blastula, gastrula, and prism embryos, while no binding to nuclear fractions of early and more advanced plutei was detected. 6. Results of binding studies support developmental stage-specific regulatory roles of serotonin during sea urchin embryogenesis.