| Abstract: | A decreased rate of L-U-14C]serine incoroporation into phosphatidylserine of polymorphonuclear leukocytes exposed to starch granules was observed. L-U-14C]serine uptake was also depressed under identical conditions. The degree of reduction in specific radioactivity of phosphatidylserine was parallel to that of L-U-14C]serine uptake. Both uptake and efflux of 45Ca2+ were enhanced in cells with starch granules, but no significant change in cellular calcium levels was detected. These results suggest that the reduced L-U-14C]serine incorporation into phospholipids may be attributable to decreased availability of this amino acid. The involvement of Ca2+ fluxes in phosphatidylserine synthesis in intact leukocytes cannot, however, be excluded. |
