Activity of different CrAT promoter constructs after supplementation with L-carnitine. TIB-73 cells cultured in medium containing 10% FCS to cause artificial L-carnitine deficiency were cotransfected either with mCrAT-1, mCrAT-2 or mCrAT-3 together with pCMV-ßgal and supplemented with increasing concentrations of L-carnitine for 4 hours. Luciferase activity was normalized for ß-gal activity. Data represent the mean ± SD, n = 4; the mean value for non-supplemented cultures is designated as 1. Comparison of mCrAT-2 and mCrAT-3 constructs at all 3 supplementation levels for 10, 40 and 80 μM L-Carnitine revealed ***p-values (p < 0.001) indicated with parentheses. A Kruskal-Wallis test for all three constructs resulted in slightly less significant p-values (p = 0.094 for 10 μM L-carnitine, p = 0.0002 for 40 and 80 μM L-carnitine).