SPHK activity in tissues and blood from Sphk2-null mice. SPHK enzymatic activity in homogenates of tissues and in whole blood from Sphk2-null and WT mice. The assays were performed in buffers favoring SPHK1 activity (A) or SPHK2 activity (B). Values represent mean ± SD, with n = 3. Statistical significance was calculated using Student t test (^**P < .01); no statistical significance was reached in panel A.