Improvement in liver fibrosis, functionality and hemodynamics in CCI4-cirrhotic rats after injection of the Liver Growth Factor.

BACKGROUND/AIMS: Most substances used in experimental models of cirrhosis are chosen either as protectors of lipid peroxidation, as antifibrogenic agents or as vitamins, among others. In this report, we analyze the improvement produced, in established cirrhosis (CCl4 plus phenobarbital) in rats, by intraperitoneal injection of Liver Growth Factor, a hepatic mitogen with activity both in vivo and in vitro. METHODS: Following confirmation of CCl4-induced cirrhosis, Liver Growth Factor (4.5 microg per ratx2 injections/week for 3 weeks) was administered to one group of rats (Cirr+LGF). The remaining rats (Cirr) received saline. The groups were compared in terms of serum enzymes, tissue damage, total liver collagen, collagenase activity, microsomal enzyme activities, splanchnic and systemic hemodynamics and portosystemic shunting. RESULTS: Treatment of rats presenting CCl4-induced cirrhosis with Liver Growth Factor decreased serum aminotransferase levels and increased levels of serum albumin and total protein. The Liver collagen content was lower in rats treated with Liver Growth Factor (2.96 vs. 4.32 mg/g liver, p<0.01). Microscopic studies revealed that the livers of rats receiving Liver Growth Factor showed decreases in fibrosis, necrosis and inflammatory infiltration, as well as a recovery of architectural integrity. Liver function was improved after treatment with Liver Growth Factor, as indicated by the rate constant for elimination of aminopyrine, which increased from 0.0063 to 0.0170 (p<0.05). This increase was accompanied by a higher total amount of cytochrome P-450 as well as of certain P-450 isoenzymes, especially those that are hormone-dependent, such as P-450 3A. The improved liver histology and function observed in Cirr+LGF rats was associated with decreases in portal pressure (14.4 vs. 9.4 mm Hg, p<0.01) and portosystemic shunting (55.8 vs. 11.5%, p<0.01), as well as increases in mean arterial pressure and systemic vascular resistance, and a reduction in ascites. CONCLUSIONS: Administration of the hepatic mitogen, Liver Growth Factor, to CCl4-cirrhotic rats decreased liver collagen and reorganized the hepatic extracellular matrix, resulting in an improvement in liver function, reduced portal pressure and amelioration of ascites.

Hepatic growth induced by injection of the liver growth factor into normal rats.

Normal Wistar rats injected with the liver growth factor (LGF), a mitogen specific for liver cells, experienced hepatic growth. LGF shows two peaks of activity in vivo, both of them mitogenic. Rats injected either with 6.8 ng or 3.9 micrograms LGF/rat every 3-4 days experienced liver growth showing a see-saw profile. Dry liver weight usually peaked at day 2 (microgram doses) or at day 3 (ng doses) after each injection, with increases of about 30% over controls. Liver DNA synthesis, measured by [3H]-thymidine incorporation, peaked 24 h after LGF injection at both doses. Liver protein synthesis, measured by [14]C-leucine incorporation, usually peaked 24 h after DNA synthesis maximums. Mitogen-stimulated cells were also assessed by immunohistochemical staining for proliferating cell nuclear antigen in livers of LGF-injected rats. Rats injected with rat serum albumin purified from normal rats to serve as controls showed a 6% increase in dry liver weight, but when serum albumin from 3-day fasted rats was injected instead, the increase was not statistically significant. The mild effect of rat serum albumin could be due to the lipid content of the solutions injected, but the level of lipids/mg protein in LGF solutions was half that determined with serum albumin from 3-day fasted rats. From the microscopic and ultramicroscopic studies carried out in rat livers injected with LGF at each dose, we observed: (1) an increase in the number of hepatocytes undergoing mitosis; (2) transient increases in lipid and glycogen contents, as occur after liver resection; (3) no signs of degeneration, such as the appearance of amyloids or fibrosis; (4) no increase in lysosome number, as in hepatotoxicity; (5) no alterations in endothelial or Kupffer cells; and (6) no ultrastructural signs of degeneration either in cytoplasmic organelles (rough endoplasmic reticulum, mitochondria) or in nuclei. One year after LGF injection, rat liver, pancreas, kidneys and spleen were normal, with no signs of degeneration or onset of fibrosis.