Sodium and chloride co-transport by preimplantation rabbit blastocysts.

Influxes of Na+ and Cl- across the trophectodermal epithelium of 6 day post coitum (p.c.) rabbit blastocysts are partially interrelated. This relationship was investigated under conditions in which either the external [Na+] or [Cl-] concentration was varied. Our results indicate that an ouabain-insensitive, furosemide-sensitive, Na+:Cl- co-transport system exists in the 6 and 6.5 day p.c. rabbit embryo, but not in the 5 day p.c. blastocyst. There was no dependence of NaCl uptake on the presence of K+ in the bathing medium. No evidence of Na+/H+ or Cl-/HCO3- exchange systems in the rabbit blastocyst was found. The effects of furosemide, exogenous cyclic AMP, and various exogenous prostaglandins on Na+ and Cl- movements were studied. Cyclic AMP and/or prostaglandin E1 may regulate the operation of this Na+:Cl- co-transport system.