Influences Of Tetrahydrobiopterin On Endothelial Function In Rabbits With Hypercholesterolaemia

Objective To examine the effect of tetrahydrobiopterin , anessential cofactor for nitric oxide synthase, on endothelial dysfunction in hypercholesterolaemic rabbits.Methods Twenty-four rabbits were divided into four groupsrandomly, received normal diet( A group, n=8) or cholesterol diet ( B group, n=8) or cholesterol diet plus folic acid( C group, n=8) or cholesterol diet plus tetrahydropterin( D group, n=8) for 30 days, respectively. After plasma TC and NO concentration were measured, thoracic aortas were removed and cut into ring segments about 3mm long, then the endothelium-dependent maximal relaxiation to Ach or ATP or SNG by accumulated concentration were obtained .Results Compared with A group, the TC concentration in B and Cand D groups were markedly increased (4. 06 + 0. 55mmol/l vs 21. 13 + 6. 67, 17. 95 + 6. 18, 28. 70 6. 55mmol/l, P<0. 01) ; there were no diffence between C or D and B groups (P>. 05) . Compared with A group, the NO concentration in B and C and D group was markedly decreased (45. 42 + 10. 56, 66. 30+12. 84, 78.33+19.03 umol/L vs 122.95 + 13.03 umol/L, P<0. 01) ;Compared with B group, the NO concentration in C group were markedly increased (P<0. 05) ; Compared with B group, the NO concentration in D group were markedly increased (P<0. 01) . Compared with A group, the maximal relaxations of arterioles induced by Ach were markedly decreased in B group(40. 37 + 12. 56 vs 143. 85 + 27. 61um,P<0. 01); Compared with B group, the maximal relaxations of arterioles induced by Ach were markedly increased in C and D group (62.03 + 13.27, 94.75+19.16 vs 40.37 +12. 56um, P<0.01) . Compared with A group, the maximal relaxations of arterioles induced by ATP were markedly decreased in B group(42. 78 10. 24 vs 120. 30 26. 32um,P<0. 01), Compared with B group, the maximal relaxations of arterioles induced by ATP were markedly increased in C and D group (72. 07 20. 68, 108. 70 19. 81 vs 42. 78 10. 24 um, P<0. 01) . There were no diffence among all groups with the maximal relaxations of arterioles induced by SNG (72. 09 23. 02 vs 62. 32 21. 37 vs 68.32 21.86 vs 67. 79 18. 63um, P>0. 05) .Conclusion Hypercholesterolemia results in the endothelialdysfunction , tetrahydrobiopterin and folic acid restore endothelial function in rabbits with hypercholesterolaemia .