Effects of beta-carotene and vitamin A on oval cell proliferation and connexin 43 expression during hepatic differentiation in the rat(1)

The effects of β-carotene and vitamin A administrations were evaluated in an in vivo model of hepatic cell differentiation. For this purpose, male Wistar rats received β-carotene (70 mg/kg of body weight), vitamin A (10 mg/kg of body weight) or corn oil (control group), by gavage and at every other day during the entire experimental period. After 4 consecutive weeks of treatment, the animals were submitted to the AAF/PH model of hepatic cell differentiation (6 × 20 mg of AAF 2-acetylaminofluorene]/kg of body weight and partial hepatectomy) and killed on different days following the surgery (until day 16 after hepatectomy). Liver samples were collected for determination of β-carotene, retinol and retinyl palmitate concentrations, for histopathological (hematoxilin-eosin) examination, for immunohistochemical detection of glutathione S-transferase, as well as for the evaluation of connexin 43 (a structural protein of gap junctions of oval cells) expression by northern blot analysis. Compared to controls, the oval cell proliferation peaks (observed by histopathological examination and immunohistochemistry) and connexin 43 expression peaks, were postponed to later days after hepatectomy, in a similar way in β-carotene and vitamin A treated animals. Compared to the other experimental groups, the vitamin A treated group showed an increase in connexin 43 expression. It was concluded that β-carotene and vitamin A modulated oval cell proliferation and connexin 43 expression, delaying both events. These findings suggest that β-carotene and vitamin A can modulate the hepatic differentiation process in vivo.