Hepatic regeneration in vitamin A-deficient rats: changes in the expression of transforming growth factor alpha/epidermal growth factor receptor and retinoic acid receptors alpha and beta.

We have studied the effect of vitamin A deficiency on the expression of transforming growth factor alpha (TGF-alpha), hepatocyte growth factor, acidic fibroblast growth factor, and TGF-beta 1 after partial hepatectomy of vitamin A-supplemented and vitamin A-deficient rats. In addition, the expressions of epidermal growth factor receptor and retinoic acid receptors alpha (RAR alpha) and beta (RAR beta) were studied. Partial hepatectomy was performed on the animals from the vitamin A-supplemented and -deficient groups at the age of 10 weeks when the weights of the animals on the deficient diet had reached a plateau. Two animals from each group were sacrificed before the operation and also 12, 24, 48, and 72 h and 5 days after the operation. Partial hepatectomy of the vitamin A-deficient rats leads to a focal necrosis of liver followed by a rapid restoration of liver mass. Expression of the TGF-alpha and epidermal growth factor receptor was highly elevated in the livers of deficient animals after partial hepatectomy. In the vitamin A-supplemented animals, the level of epidermal growth factor receptor was down-regulated following partial hepatectomy. Proliferation of oval cells in vitamin A-deficient livers following partial hepatectomy and subsequent increase in 2.1-kilobase alpha-fetoprotein mRNA was observed, suggesting an activation of the stem cell compartment. Another unexpected result was an inverse relationship between RAR beta and RAR alpha expression, the latter becoming the major species after partial hepatectomy in animals on the vitamin A-deficient regimen.(ABSTRACT TRUNCATED AT 250 WORDS)