FIG. 5.

Determination of plasma ATX activity, LPA, and S1P levels. (A) Half-normal plasma LPA levels in heterozygous ATX mice (86 ± 14 nmol/liter versus 181 ± 17 nmol/liter in the wild types). LPA levels were determined by the generation of phosphatidic acid, produced by the transfer of a ¹⁴C fatty acyl chain onto LPA (38). Values correspond to means ± standard errors of the means (n = 4). (B) ATX activity in serum as determined by CPF4, the FRET-based ATX sensor (2 μM) (52). Relative ATX activity was calculated as the decrease in the FRET ratio (+/+, n = 7; +/−, n = 5). a.u., arbitrary units. (C) Normal plasma S1P levels in heterozygous mice, as determined by liquid chromatography-mass spectrometry (heterozygote, n = 10; wild type, n = 13).