Effects of the coadministration of thiamine on the incidence of urinary bladder carcinomas in rats fed bracken fern.

Abstract

Summary Bracken fern ( Pteris aquilina ), mixed with a grain mixture (1:3 by weight), was fed to two groups of male and female albino rats. In Group 1, which was fed bracken fern but received no thiamine supplements, all rats surviving more than 6 months developed various combinations of multiple intestinal adenomatous polyps or adenocarcinomas. However, only 1 of 9 males (11%) and 1 of 13 females (8%) in Group 1 developed urinary bladder carcinomas. The rats of Group 2, fed bracken fern and given additionally 2 mg of thiamine hydrochloride s.c. once each week, also developed a 100% incidence of multiple intestinal tumors. Moreover, 19 of 36 males (53%) and 35 of 51 females (69%) in Group 2 had urinary bladder carcinomas. The incidence of the bladder carcinomas in either males or females in Group 2 was significantly greater ( p