Biology of Reproduction, Vol 11, 654-662, Copyright © 1974 by Society for the Study of Reproduction

Rabbit Blastocoele Bicarbonate: Accumulation Rate

¹ Laboratory of Reproductive Physiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104

The blastocoele cavity of rabbit blastocysts was filled with the same solution (Eagle's with 24 mM HCO₃^- and 20% calf serum) used to bathe the embryos. After 4 h of incubation at 37°C in 5% CO₂ in air, the concentrations of bicarbonate and free CO₂ (microgasometry) in the blastocoele fluid increased, respectively, by an average of 30 and 26% over the values in the bathing solution, while the pH of blastocoele fluid (antimony microelectrode) remained constant. Acetazolamide (1 mM), added to the solutions on both sides of the blastocoele wall, did not inhibit bicarbonate and CO₂ concentration increases and did not significantly decrease water transport. The average rate of bicarbonate transport was 32 nmoles/blastocyst/h and is in good agreement with the nonsodium and nonchloride component of the short-circuit current. These data, together with our electrical data, are consistent with the hypothesis holding that bicarbonate accumulation in the rabbit blastocoele is due to active bicarbonate transport.