Abstract: We studied the absorption of nattokinase NK-01 in the intestine of rats.The absorption of NK-01 was verified by the everted gut sacs method in vitro.Based on this,NK-01 was labelled with FITC,and injected into duodenum of rats.Then,enzyme activity and fluorescence intensity of FITC-NK-01 were measured in rat plasma,which could reflect the absorption of NK-01 in vivo.After treated with FITC-NK-01,the enzyme activity and fluorescence intensity were detected in plasma of rats at 2 h.At 4 h,the enzyme activity and fluorescence intensity in the rat plasma reached a maximum,and then began to decline.Meantime,the change of fluorescence intensity is consistent with the enzyme activity of the FITC-labeled NK-01 in the rat.Therefore,the metabolism of NK-01 can be characterized by the change of fluorescence intensity in vivo,which provides a new method for the metabolic and quantitative studies of it in vivo.

Key words: Nattokinase, duodenum, absorption, fluorescence labeling