The effects of the Bowman-Birk protease inhibitor on c-myc expression and cell proliferation in the unirradiated and irradiated mouse colon.

The levels of c-myc RNA and crypt cell proliferation were monitored in the mouse colonic mucosa following X-irradiation with and without oral administration of the Bowman-Birk protease inhibitor (BBI). Mice were divided into 4 groups and treated as follows: (A) daily gavage with water; (B) daily gavage with BBI; (C) daily gavage with water and 12 Gy of abdominal irradiation 1 day after the first gavage; (D) daily gavage with BBI and 12 Gy of abdominal irradiation 1 day after the first gavage. Samples were collected at various times after X-irradiation and ascending colon samples were taken for crypt cell proliferation analysis. The mucosa was removed from the remaining sample and total cellular RNA was isolated. The levels of c-myc mRNA underwent a time-dependent change following X-irradiation. Expression of the c-myc gene was unchanged at 1 day and 3 weeks after irradiation, but was markedly elevated at 1 week after X-irradiation. BBI was found to suppress the radiation induced elevation of c-myc mRNA, while having no effect on the rate of crypt cell proliferation or body weight of the mice.