Retinol-binding proteins in human testis cytosol

Levels of vitamin A and cellular retinol binding protein in human hepatocellular carcinoma and adjacent normal tissue

The levels of vitamin A (retinol) and vitamin E were measured in the blood, in tissues of human hepatocellular carcinoma (HCC), and in adjacent liver parenchyma. The median values of vitamin A were 11.5 micrograms/g (ranging 0-82.5 micrograms/g) in HCC and 52.1 micrograms/g (ranging 0.4-895.2 micrograms/g) in normal liver tissues; the difference was statistically significant (p less than 0.05). By contrast, there was no significant difference in vitamin E levels between the two tissues. Although the levels of vitamin A were significantly lower in HCC in 10 patients, no significant difference was noted in the cellular retinol binding protein levels in the normal and malignant tissues. These results suggest that the decreased levels of vitamin A in HCC are not due to altered cellular retinol binding protein levels in tumors and the different vitamin A blood supply system. We conclude that either the decreased uptake of vitamin A, but not vitamin E, by HCC cells or the lack of vitamin A-storing cells in tumors might be responsible for the low levels of vitamin A in HCC.

Cellular vitamin A-binding proteins in liver tumors and adjacent tissues

The levels of cellular retinol-binding protein (CRBP) and retinoic acid-binding protein (CRABP) were assessed in surgically resected ten human liver tumors and their adjacent tissues by sucrose density gradient centrifugation and Scatchard analysis. The tissues adjacent to hepatocellular carcinomas usually showed portal cirrhosis or hepatitis. There was no significant difference in the dissociation constant (Kd) values of binding proteins of CRBP or CRABP between tumors and adjacent tissues. Five of the ten liver tumors showed similar levels of CRBP as in their adjacent tissues whereas three of the ten liver tumors showed about 40% or less contents of CRBP in comparison with their adjacent tissues and two others had no CRBP activity. By contrast, CRABP activities were found in five liver tumors and in adjacent tissues of one case, whereas there were no detectable CRABP activities in the adjacent tissues except in one case.