Growth stimulation of rat colonic cells in organ culture with N-methyl-N'-nitro-N-nitrosoguanidine.

The effects of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) on rat colonic mucosa were investigated in organ culture. Distal colonic mucosa separated from the muscle layers was cultured on a substrate of human fibrin foam. Exposure of colonic organ cultures to 0.1, 1.0, and 10.0 micrograms MNNG/ml of medium on a multiple discontinuous basis, e.g., every third day for 3 hr, produced significant carcinogen effects. [3H]Thymidine was incorporated throughout crypts and in surface epithelium of carcinogen-treated explants. Outgrowth of epithelioid cells into the fibrin foam matrix was observed in all treated explants 9 days after initial MNNG exposure. Control untreated cultures showed limited outgrowth. After 15 and 21 days in culture, epithelioid outgrowth was still observed in 1.0 microgram MNNG/ml-treated cultures.