Low NA + concentration: A factor contributing to diminished uptake and incorporation of amino acids by diapausing mouse blastocysts? This study was supported by The University of Michigan-Dearborn Faculty Research Grant 238592.

Uptake and incorporation of 14 C amino acids by normal and diapausing blastocysts was found to be Na + dependent with one exception. Delayed embryos preincubated 25 h in medium containing 124 mM Na + had labeling characteristics independent of the Na + concentration present during labeling. Since diapausing embryos preincubated 25 h in low Na + medium (55 mM) retained their Na + dependent labeling characteristics, delayed blastocysts may be in a low Na + environment in situ. Low Na + may explain why delayed blastocysts are unable to utilize radioactive methionine in vivo (Weitlauf and Greenwald, '68).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38083/1/1402020218_ftp.pd