Phosphate induced developmental arrest of hamster two-cell embryos is associated with disrupted ionic homeostasis

Culture of hamster embryos with 0.35 mM inorganic phosphate results in deve lopmental arrest at the 2-cell stage. These arrested 2-cell embryos were fo und to have significantly elevated levels of both intracellular pH and intr acellular free calcium. Culture of 2-cell embryos with both glucose and pho sphate did not further alter intracellular ionic homeostasis. Developmental arrest of 2-cell embryos was dependent on the concentration of phosphate u sed. Culture with 1.25 mu M phosphate did not alter development, while conc entrations of 2.5 mu M and 5.0 mu M resulted in a percentage of embryos arr esting development at the 2-cell stage. Analysis of intracellular levels of pH and calcium after culture with different phosphate concentrations revea led a significant negative correlation between intracellular calcium levels and development beyond the 2-cell stage. There was no correlation between the increase in intracellular pH and embryo development in the presence of phosphate. The increase in intracellular calcium levels after culture with phosphate appears to be derived from intracellular pools, as preventing the influx of extracellular calcium did not alter development beyond the 2-cel l stage. Therefore, it is apparent that a disruption in ionic homeostasis i s associated with developmental arrest of hamster embryos cultured with pho sphate; (C) 1999 Wiley-Liss, Inc.