Reducing inositol lipid hydrolysis, Ins(1,4,5)P3 receptor availability, or Ca2+ gradients lengthens the duration of the cell cycle in Xenopus laevis blastomeres.

摘要: We have microinjected a mAb specifically directed to phosphatidylinositol 4,5-bisphosphate (PIP2) into one blastomere of two-cell stage Xenopus laevis embryos. This antibody binds endogenous PIP2 and reduces its rate hydrolysis by phospholipase C. Antibody-injected blastomeres undergo partial or complete arrest the cell cycle whereas uninjected sister divided normally. Since normally produces diacylglycerol (DG) inositol 1,4,5-triphosphate (Ins[1,4,5]P3), we attempted measure changes in levels DG following stimulation antibody-injected oocytes. The total amount oocytes was significantly reduced compared that water-injected ones either acetylcholine progesterone indicating does indeed suppress hydrolysis. also found antibodies greatly intracellular Ca2+ released egg cortex during activation. As an indirect test for Ins(1,4,5)P3 involvement injected heparin which competes with binding receptor, thus inhibits Ins(1,4,5)P3-induced release. Microinjection embryo caused depending upon concentration injected. further investigated effect reducing any [Ca2+]i gradients microinjecting dibromo-BAPTA blastomere. Dibromo-BAPTA injection completely blocked mitotic division when final 1.5 mM used. These results suggest turnover as well second messenger activity influence duration embryonic frogs.