RESUMO
Conditioned media of Kupffer cells from normal rat liver produce in culture two factors that inhibit fibroblast proliferation. The inhibitory factors have molecular masses of approximately 25 and 5 kDa. In contrasts to these results, the conditioned media of Kupffer and mononuclear macrophagic cells, obtained 48 hours after CC1(4) administration to rats, contains a 17 kDa factor that stimulates fibroblast proliferation (FSF). FSF also stimulates [3H]-thymidine incorporation into DNA of cultured rat liver fat-storing cells. Two peaks with FSF activity were demonstrated after isoelectrofocusing; one with a pI of 6.1 and a second with a pI of 7.5. The fraction containing FSF is devoid of interleukin-1 (IL-1) activity and no inhibitory activity is detected in this conditioned media. Production of FSF is inhibitable by colchicine but not by indomethacin, it is thermolabile and trypsin-sensitive. In animals treated chronically with CC1(4) to produce cirrhosis, FSF activity is demonstrable from the first to the 8th week of treatment. However, the activity is lower at 8 weeks post-CC1(4) as compared with 2 weeks. The results suggest that homeostasis of cells in the liver is controlled by factors produced locally, that act by autocrine and paracrine mechanisms. When homeostasis is altered, fibroblast proliferation occurs, and excess collagen deposition leads to fibrosis. We propose that the antifibrogenic activity of colchicine is associated, in part, with its capacity to inhibit the release of FSF by Kupffer cells and liver mononuclear macrophage cells.