Extraction of vanadium‐binding substance (vanadobin) from a subpopulation of signet ring cells newly identified as vanadocytes in ascidians

We have previously extracted vanadobin, a substance binding vanadium ions in ascidian blood cells. The present study examined which of several types of blood cell contains this substance, using a combination of cell fractionation, chromatographies, and neutron activation analysis. The vanadium‐containing blood cell type, so‐called vanadocyte, is the signet ring cell in Ascidia sydneiensis samea as well as A. ahodori, and vanadobin was extracted from a homogenate of signet ring cells, but not from morula cells, although the latter have previously been considered to be the vanadocytes.