| 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. |
