Mechanisms Implicated in the Response of System A to Hypertonic Stress and Amino Acid Deprivation Still Can Be Different

Alfieri et al. (2004) analyzed the response of system A to hypertonic stress by determining changes in SNAT2 mRNA levels in a panel of cell lines, including the same cell type, CHO-K1, that we routinely used in the past for this kind of studies. It is evident that a discrepancy between their results and ours regarding the effect of hypertonicity on SAT2/SNAT2 mRNA levels exists. Our CHO-K1 clone was originally obtained from E. Englesberg (University of California, Santa Barbara, CA), who developed a panel of somatic mutant cell lines with altered system A activity and regulatory properties (Moffett and Englesberg, 1984, 1986; Englesberg and Moffett, 1986; Moffett et al., 1987; Qian et al., 1991; among others). In our experiments, the SAT2/SNAT2 cDNA probe used for Northern blot analysis was a fragment cloned from that particular cell line (this is...