12-0-Tetradecanoyl-Phorbol-13-Acetate Release of

human blood by Ficoll-Hypaque centrifugation contained and released sialyltransferase, galactosyl-transferase, and fucosyltransferase. Granulocytes contained and released lesser amounts of glycosyltrans-ferases, whereas platelets released more fucosyltrans-ferase than sialyltransferase or galactosyltransferase. When mononuclear cells were incubated with 12-0-tetradecanoyl-phorbol-13-acetate (TPA), the release of these three glycosyltransferases increased two- to six-fold, and cell suspension glycosyltransferase activities decreased 10-50%. Mononuclear cells were frac-tionated into lymphocytes and monocytes using baby hamster kidney cells microexudate-coated flasks. TPA stimulated the release of glycosyltransferases from lymphocytes but not from monocytes. The release of glycosyltransferases by TPA-treated mononuclear cells was not further stimulated by reincubation with TPA and was not affected by puromycin, cAMP, or cGMP. Concanavalin A, a mitogenic stimulator of lympho-cytes, also stimulated the release of glycosyltrans-ferases from mononuclear cells, but to a lesser extent. TPA did not stimulate the release of 5'-nucleotidase or decrease its activity on the cell pellet. Triton X-100 (0.2%) stimulated the release of glycosyltransferases to the same extent as TPA, but also caused the release of 5'-nucleotidase. [3H]TPA bound specifically and re-versibly to mononuclear cells. The possible relation-ship between glycosyltransferase release and TPA ef-fect on the plasma membrane is discussed