Modulation of amino acid transport in preimplantation mouse embryos by low concentrations of non-ionic and zwitterionic detergents

Abstract

In 4-cell embryos (but not in blastocysts), Triton X-100, a non-ionic detergent, stimulated leucine, phenylalanine, methionine and glutamic acid transport from 1.6 to 3.2-fold. All of these amino acids were transported exclusively by a sodium-independent mechanism. Triton X-100, however, did not stimulate the transport of other amino acids tested in 4-cell embryos. Furthermore, phenylalanine transport rates were stimulated about 2-fold at the 4-cell stage by all of the non-ionic and zwitterionic detergents tested at concentrations which were approximately one-tenth of the critical micellar concentration for each detergent. These concentrations did not block development, disrupt the cells, or make the cell membranes freely permeable. At the blastocyst stage, Z312, a zwitterionic detergent, inhibited the transport of phenylalanine and alanine and stimulated the transport of lysine, a pattern previously found to be linked to the sodium-dependent amino acid transport mechanism. We suggest that Z312 may be acting upon some component of sodium-dependent amino acid transport in blastocysts. The non-ionic and zwitterionic detergents seemed to have a common effect on amino acid transport in 4-cell embryos but elicited varied transport responses from blastocysts. These differential responses to detergents by blastocysts may reflect intrinsic changes in membrane composition and/or organization which occur during the normal course of preimplantation development.

Glutamine uptake and utilization by preimplantation mouse embryos in CZB medium

“…Glutamine uptake was constant at the unfertilized egg and 1-cell stages and increased rapidly at the 8-cell, morula and blastocyst stages. These results are consistent with observations on the uptake of several other amino acids, in particular, methionine, lysine, alanine, phenylalanine, glutamic acid and leucine, by preimplantation stage mouse embryos (Monesi & Salfi, 1967;Epstein & Smith, 1973;Borland & Tasca, 1974Kaye et ai, 1982;Keefer & Tasca, 1984;Van Winkle, 1988). The present observation of a decline in glutamine uptake at the 2-cell stage before a rapid increase in accumulation at the 8-cell stage is consistent with the pattern of leucine uptake described by Monesi & Salfi (1967) and Epstein & Smith (1973).…”

Analysis of stimulatory and inhibitory amino acids for development of hamster one‐cell embryos in vitro

“…This switch in the nitrogen requirements occurs at a time when the developing embryo is making a transition from cleavage stages to differentiation of inner cell mass cells and trophectoderm cells. An increase in protein metabolism (Schultz et al, 19811, changes in endogenous pools of amino acids (Schultz et al, 1981;Sellens et al, 1981;Chatot et al, 1990) and changes in amino acid transport mechanisms (Borland and Tasca, 1974;Kaye et al, 1982;Keefer and Tasca, 1984;Hobbs and Kaye, 1985) are concomitant events during this transition in mouse embryo development. The amino acid (and energy substrate) requirements for hamster embryo development and differentiation in vitro presumably change over time since embryos in vivo encounter different secretory regions of the reproductive tract as they develop (Leese, 1988;Bavister, 1995).…”

Recipient of the 2022 IETS Pioneer Award: Dr Carol Keefer

“…That initial experience with reproductive biology led Dr Keefer to pursue graduate studies in developmental biology with the distinguished Dr Dick Tasca at the University of Delaware, where she earned a PhD in Biological Sciences in 1981. Dr Keefer revealed that her alternate plan was to study evolutionary genetics, but she was listed as only an alternate for a stipend at Stanford and so chose to study amino acid transport in preimplantation mouse embryos for her PhD dissertation work (Keefer and Tasca 1984). We owe Stanford a debt of gratitude for unknowingly steering Dr Keefer along her path of exemplary contributions to the field of Reproductive Biology!…”