Hepatic lipase activity in fasted mice measured in pre and postheparin plasma. Activity units are mU/ul. HL−/− = mice lacking endogenous HL; HL+/− = F1 (C57BL6/J X HL−/− mice); HL+/+ = C57BL6/J mice; HL−/−,+S = mice lacking endogenous HL and positive for the SPRET-HL transgene; HL+/+,+S = C57BL6/J mice positive for the SPRET-HL transgene. Ns are as follows for preheparin plasma: females HL−/− 14; HL+/− 9; HL+/+ 15; HL−/−,+S 12; HL+/+,+S 10; and males HL−/− 13; HL+/− 7; HL+/+ 10; HL−/−,+S 9; HL+/+,+S 9. For postheparin plasma, N = 3 for HL+/+ and N = 4 for HL−/−,+S mice. Data shown are means ± SEM. Sexes were analyzed separately. **P < 0.0001 compared with all other HL genotypes and *P ≤ 0.008 compared with HL+/+; HL−/−,+S; and HL+/+,+S for females; and HL−/−,+S and HL+/+,+S for males by Sidak's t-test for multiple comparisons.