The evidence that phospholipase A activity may serve as a metabolic site for modulation of palate formation includes the findings that (1) palate mesenchyme cells synthesize prostaglandins which will elevate intracellular levels of cAMP in such cells and stimulate them to synthesize extracellular matrix macromolecules, (2) cAMP will regulate phospholipase activity and prostaglandin synthesis by palate mesenchyme cells, (3) concentrations of glucocorticoids which induce cleft palate in glucocorticoid-sensitive strains of mice also inhibit specific phospholipase activities in cells from such strains, and (4) glucocorticoids disrupt programmed cell death as it normally occurs in the medial edge epithelium of the palate; phospholipase activity has been implicated as regulating some forms of cell death. Therefore, these studies aim to test the hypothesis that mobilization and metabolism of arachidonic acid by specific metabolic pathways is a regulatory event in development of the secondary palate. Thin layer chromatography, scintillating spectrometry, subcellular fractionation, biosynthesis of radiolabeled substrates will be used to assess the specific phospholipases altered by glucocorticoid-treatment of primary cultures of cells from glucocorticoid-sensitive and less sensitive strains of mouse embryos. Relations between mobilization and metabolism of arachidonic acid and programmed cell death in palatal epithelium will be determined by column chromatography, gas liquid chromatography, and scintillation spectrometry. The metabolites of arachidonic acid present during normal and abnormal ontogenesis of the palate will be determined by column chromatography and gas liquid chromatography. The objectives of the proposed research are: (1) to determine cellular location of the specific phospholipid hydrolase activity which is altered by a teratogenic dose of glucocorticoid, (2) to determine whether there is a pattern of snythesis of eicosanoids which may be correlated with normal and abnormal development of the palate, and (3) to explore the possibility that phospholipase activity is causally related to programmed cell death in the palate.
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