Antitumor promoting effect of an active component of polyporus, ergosteroland related compounds on rat urinary bladder carcinogenesis in a short-term test with concanavalin A

The effect of fractions from a water extract of Polyporus on bladder tumor promotion was examined using 5% sodium saccharin (SS) in a short-term test with concanavalin; A (Con A) in Wistar rats. Rats were given N-butyl-N-(4-h ydroxybutyl) nitrosamine (BHBN) in drinking water for one week, and then pr omoter alone ol test samples (given orally) plus promoter was administered for 3 weeks. Treatment with the BuOH fraction isolated from the water extra ct showed a strong inhibitory effect against the promoter. It was found tha t the inhibitory effect of the BuOH fraction is due to the effect of ergost erol contained in the fraction. Treatment with ergosterol showed a strong i nhibitory effect against 5% SS, 0.01% BHBN, 3% DL-tryptophan (Trp) or 2% bu tylated hydroxyanisole (BHA); ID50 was 1.4 mug/kg/d, 2.9 mug/kg/d, 11.6 mug /kg/d, and 11.7 mug/kg/d against SS, BHBN, Trp and BHA. respectively, We al so examined the effect of steroids and related compounds. Squalene and vita min D-2 showed strong inhibitory effect against 5% SS-induced bladder tumor promotion, These results strongly suggest that ergosterol could provide si gnificant protection against the promotion of bladder tumor induced by many types of promoters in the environment.