膀胱腫瘍の発生機構にかんする実験的研究 -- とくにtryptophanおよび肝機能の役割について--

Abstract

Young male rats of Wistar strain were divided into several experimental groups, each consisting of 30 animals, and fed on different diet as follows: Group A: vitamin Be deficient basal diet with 0.04 % 2-acetylaminofiuorene (2-AAF) Group B: same as group A plus 1.4 % d, L-tryptophan Group C: same as group B plus sufficient quantity of vitamin Be (pyridoxal phosphate). The animals of each group were sacrificed at 9, 15 and 30 weeks. Various organs including the bladder and liver were histologically examined. Calculation of labeling index of 3H-TdR(6-nT) uptake by the urinary bladder mucosa as well as measurement of liver function by indocyanine green test (I. C. G. test) was accomplished. Orally given 2-AAF gave typical damages to the liver within 9 weeks, causing cystic formation, hyperplastic nodule and proliferation of tubular duct with fibrosis. Some significant relationships were observed among relative weight of the liver, I. C. G. test and labeling index of the bladder mucosa. On the other hand, the bladder epithelium turned its nature as time goes on and the epithelial hyperplasia was observed 15 weeks after initiation, then some of them altered to papillary tumor of the bladder. There must be more complicated factors between hyperplasia and cancer formation which is an irreversible process. There was apparently negative correlation between serum retention rates of I. C. G. and labeling indices of the bladder mucosa at 15 and 30 weeks in each group. This suggests presence of some activation mechanism in the rat which will metabolite carcinogens to more proximate substances by passing through liver cells. The mechanism may be consistent with so-called "liver-bladder axis" which Melicow and others advocated previously. Although tryptophan-annexed diet in group Band C gave a protecting effect to the liver against 2-AAF, vitamin Be seemed not to ensure a role of liver defense.