Quantitative Real Time PCR Confirmation of Species-Specific ER Regulation of Ca2. The temporal gene expression of carbonic anhydrase 2 (designated Car2 in the mouse and Ca2 in the rat and human, hereafter referred to as Ca2 to represent all orthologs) was further validated by species-conserved and -unique primer sets. The QRT-PCR results confirm the microarray results indicating that Ca2 is differentially regulated in the mouse when compared to the rat. This differential regulation was elicited by both EE and TAM. Mouse Ca2 expression is significantly (p < 0.05) induced while rat expression is significantly (p < 0.05) repressed (n = 5, Tukey's HSD post hoc test), at multiple time points as indicated by the asterisk (*).