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Regular Article |
a Loeb Research Institute, Ottawa Hospital, and
b Departments of Obstetrics and Gynecology,
c Division of Reproductive Medicine, and Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada K1Y 4E9
d Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison, Wisconsin 53706
ABSTRACT
Regulation of intracellular pH (pHi) by two-cell-stage embryos derived from female mice of three different strains (CF-1, Balb/c, and BDF) was investigated. Embryos recovered at a slow rate from intracellular acidosis produced by a pulse of NH4Cl; the rate did not differ significantly among strains. Recovery was reversibly inhibited by amiloride or the absence of Na+, implicating Na+/H+ antiporter activity. The threshold pHi (setpoint) below which Na+/H+ antiporter activity was elicited was approximately 7.15 for each strain. No recovery from induced acidosis occurred in the absence of external Na+ in any strain, and thus embryos could be maintained in acidosis for an extended period. Upon reintroduction of Na+, embryos derived from either CF-1 or BDF females recovered at a slow rate comparable to that measured in embryos not maintained for a period in Na+-free medium, but embryos derived from Balb/c females consistently recovered at a highly accelerated rate. This accelerated recovery appeared to be due, in part, to an activation of the Na+/H+ antiporter in Balb/c-derived embryos, which did not occur in CF-1- or BDF-derived embryos. Thus, embryos derived from different strains of female mice differ in their control of mechanisms for pHi regulation.
First decision: 26 December 2000.
1 This work was supported by an operating grant (MOP 12040) from the Canadian Institutes of Health Research (CIHR, formerly the Medical Research Council of Canada) and as part of the U.S. National Institutes of Health NICHD National Cooperative Program on Non-Human In Vitro Fertilization and Preimplantation Embryo Development (HD 22023). C.L.S. was supported by a CIHR studentship award.
2 Correspondence: Jay M. Baltz, Loeb Research Institute, Ottawa Hospital Civic Campus, 725 Parkdale Ave., Ottawa, ON, Canada K1Y 4E9. FAX: 613 761 5327 or 5365; jbaltz{at}lri.ca
3 Current address: Colorado Center for Reproductive Medicine, Englewood, CO 80110.
4 Current address: Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148.
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