COLLAGEN CONTENT IN RAT-LIVER AFTER EXPERIMENTALLY-INDUCED CHOLESTASIS FOLLOWED BY CHOLEDOCHOJEJUNOSTOMY AND X-IRRADIATION

The right part of the median lobe of the liver of female Wistar rats w as irradiated, 12.5 or 25 Gy, at a field size of 15x20 mm. The central part of the irradiated liver lobe was fixed and used for the estimati on of the collagen protein ratio by means of the Sirius Red-Fast Green extraction method, immediately, 8, 16 or 32 weeks after irradiation. No significant increase in collagen content could be demonstrated in t his time range, both after irradiation at 12.5 Gy and at 25 Gy. Partia l hepatectomy according to Higgins led to rapid regrowth of the remain ing liver lobes. The right lobe grew out rapidly to replace the median lobe. Two days after partial hepatectomy the right lobe was irradiate d at the same field size. Measurement of the collagen protein ratio in this experiment did not show a significant increase 8, 16 or 32 weeks after irradiation. However, the 25 Gy group did not survive long enou gh to obtain data at 16 or 32 weeks. The animals in this latter experi ment suffered from ascites before dying. Experimentally induced choles tasis was obtained by ligation and partial resection of the common bil e duct. After two weeks of cholestasis the bile flow was restored by R oux-en-Y choledochojejunostomy. The effect of irradiation 2 days after repair surgery was studied. Without irradiation the collagen protein ratio is increased. Irradiation of the right part of the median lobe l ed to a relatively enhanced collagen content in this lobe. Our results indicate that radiation itself does not lead to a significantly enhan ced degree of fibrosis in the liver, However when an increase in colla gen content was induced by cholestasis, the partial ''dilution'' of en hanced fibrosis as a result of proliferation of liver parenchyma cells following repair surgery was inhibited by irradiation.