TABLE 1

Inhibition of COX-1 and COX-2 by positional isomer of aspirin before and after dialysis

Ovine COX-1 or COX-2 was incubated in the presence of o-ASA, m-ASA, or p-ASA together with arachidonic acid and enzyme activity determined before and after microdialysis as detailed in Materials and Methods. Results are mean ± S.E.M. for five to seven different determinations with enzymes assays being done in triplicates.

Agent	COX-1 Inhibition (%)		COX-2 Inhibition (%)
	Before	After	Before	After
	Dialysis	Dialysis	Dialysis	Dialysis
o-ASA 1 mM	72 ± 3	72 ± 4	ND	ND
3 mM	87 ± 3	86 ± 3	83 ± 2	81 ± 2
5 mM	93 ± 4	95 ± 3	95 ± 2	95 ± 3
m-ASA 1 mM	54 ± 2^†	38 ± 2^{^*,^¶}	ND	ND
3 mM	63 ± 3^{^†}	45 ± 3^{^*,^¶}	80 ± 2	56 ± 3^{^*,^¶}
5 mM	88 ± 2	70 ± 2^{^*,^¶}	99 ± 3	76 ± 4^{^*,^¶}
p-ASA 1 mM	48 ± 2^{^†}	29 ± 1^{^*,^¶}	ND	ND
3 mM	71 ± 3^{^†}	54 ± 3^{^*,^¶}	80 ± 3	38 ± 2^{^*,^¶}
5 mM	94 ± 3	73 ± 3^{^*,^¶}	94 ± 4	67 ± 4^{^*,^¶}
Indomethacin
1 µM	69 ± 2	24 ± 1^*	67 ± 2	32 ± 2^*

ASA, acetyl salicylic acid (aspirin); COX, cyclooxygenase; ND, not done.
↵* P < 0.05 compared with before dialysis.
↵† P < 0.05 compared with o-ASA at same concentration before dialysis.
↵¶ P < 0.05 compared with o-ASA at same concentration after dialysis.