Abstract
The effect of a low-sulfur-containing medium on lysosomal arylsulfatase activities (total combined activities of A and B) was studied using primary cultured hepatocytes from rats. Liver parenchymal cells isolated from rats fed on a 10% soybean protein isalate (SPI) diet for 3 or 5 weeks showed about a 2.0-fold increase of enzyme activity in comparison with rats fed on a laboratory chow diet or a 10% casein diet. The enzyme activities were measured in cells incubated for 48 h in MEM complete medium, serum-free MEM containing 1/10 the normal level of methionine and cysteine, or serum-free MEM lacking methionine, cystine and cysteine. No increase of enzyme activity was observed in any medium containing two sets of cells prepared from rats fed on the laboratory chow, or on the casein diet, corresponding to results obtaind in vivo. The enzyme activity in cells prepared from rats fed on the SPI diet remained higher for 48 h in serumfree MEM containing 1/10 the normal level of methionine and cysteine, or in serum-free MEM lacking both amino acids, whereas a rapid decrease of enzyme activity was observed in complete MEM medium. Thus, enzyme activities in hepatocytes might change in response to the concentration of sulfur-containing amino acids in the medium.
