The effect of Kupffer cell stimulation or depression on the development of liver metastases in the rat.

Tumour cells from a squamous carcinoma (approximately 2.5 X 10(5)) were injected intraportally into a syngeneic strain of rats to produce liver metastases 14 days later. Kupffer cells were stimulated by Corynebacterium parvum (7 mg or 1 mg i.v.) and zymosan (10 mg intraportally). Kupffer cell activity was depressed by the administration of silica, gadolinium chloride or human red cells. The animals in each group were sacrificed at 14 days, the livers removed and the number of visible surface metastases counted and compared. (Mann-Whitney U-test). Kupffer cell stimulation significantly reduced the number of surface liver metastases in all animals (P 0.0048). In contrast depression of Kupffer cell activity significantly increased the number of metastases in all animals (P 0.0045), suggesting that the activity of these cells has an important effect on the development of liver metastases.