Bicarbonate requirements for culture of one-cell rabbit ova to blastocysts.

Abstract

Information on the role of bicarbonate and carbon dioxide in the development of preimplantation embryos is limited. High concentrations of HCO3 have been reported in rabbit oviducal and uterine fluids (Vishwakarma 1962; Hamner and Williams, 1964; David et a!., 1969). One function of HCO3 is as part of a buffer system and the effects of pH in bicarbonate buffered media have been studied for mouse ova (Brinster, 1965) and rabbit ova (Kane, 1974a). However culture studies on mouse ova indicate that HCO3 must possess functions other than merely acting as a buffer. Quinn and Wales (1973) reported that growth of two-cell, eight-cell and morula stages of the mouse was very limited in phosphate buffered medium and Brinster (1973, personal communication) found that in a variety of buffers one-cell or two-cell mouse ova did not develop beyond one or two divisions without HCOS and CO2. The present studies were undertaken to investigate whether this need for HCO3 applied to the rabbit ovum and, if so, at what stages of growth and what levels of HCOS were necessary. A preliminary study indicated that single-cell rabbit ova develop in N-2-hydroxyethylpiperazine-N ‘-2-ethanesulfonic acid (Hepes) buffered medium without HCOS (Kane, l974b). Hepes was chosen because of its very suitable pKa (7.55 at 20#{176}C)and other good qualities as a biological buffer (Good et a!., 1966). MATERIALS AND METHODS