Original Articles

Inhibitory effect of silybin on the activity of 5-lipoxygenase of the porcine cerebral basilar artery

Ai-you Lin, Yao-cheng Rui


The chopped porcine cerebral basilar arteries (PCBA) were incubated in the modified Tyrode solution with calcium ionophore calcimycin (A-23187, Cal) 10 mumol/L in the presence of arachidonic acid 30.6 mumol/L and indomethacin, a cyclooxygenase inhibitor 2.8 mumol/L. The culture was extracted and purified with a SEP-PAK column (SEP-PAK C18 Cartridge, Waters). The bioassay of the extract was then made on the isolated guinea pig ileum with the standard leukotriene D4 (LTD4) 200 pg/ml as a reference. The acetylcholine, histamine and 5-HT released by the ileum was preblocked by atropine 1 mumol/L, diphenhydramine 1 mumol/L and cyproheptadine 3 nmol/L. The contraction produced by the extract on the ileum showed the same characteristic as LTD4, and was blocked by the specific LTs antagonist FPL 55712 100 ng/ml. Reversed phase high performance liquid chromatography analysis indicated the presence of peaks co-chromatographing with standard LTB4, C4 and D4. The retention times of LTB4, C4 and D4 in our system were 2.2, 3.2, 5.5 min respectively. The eluates of peaks co-chromatographing with LTB4, C4 and D4 were collected and tested for contractile activity on the guinea pig ileum. Only the substances which had the similar LTC4 and LTD4 retention times exhibited contractile activities. Hence we concluded that the substances of LTs which had biological activities were mainly LTC4 and D4. The amount of LTs released from PCBA was 70 +/- 15 pg/100 mg tissue. When PCBA was preincubated with silybin 100 and 500 mumol/L, the amounts of LTs released were 27 +/- 12 and 14 +/- 6 pg/100 mg tissue, respectively (P less than 0.01).

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