Comparative subcellular distribution of benzaldehyde and acetaldehyde dehydrogenase activities in two hepatoma cell lines and in normal hepatocytes

Abstract

The NAD- and NADP-dependent aldehyde dehydrogenase (ALDH) activities were evaluated in two rat hepatoma cell lines, namely the well-differentiated MH1C1 line and the less differentiated HTC line. Each activity was determined in parallel in isolated rat hepatocytes, for comparison. The aliphatic aldehyde acetaldehyde (ACA) and the aromatic aldehyde benzaldehyde (BA) were used as substrates. With the first substrate the ALDH activities found in the crude cytoplasmic extracts were lower in hepatoma cells than in normal hepatocytes, especially when measured with NADP as coenzyme (ACA/NADP). Otherwise, with benzaldehyde as substrate the NAD-dependent enzyme activity (BA/NAD) was increased about 9-fold in HTC cells over hepatocytes and decreased in MH1C1 cells, while the NADP-dependent (BA/NADP) activity was increased 38- and 2.5-fold in HTC and MH1C1 cell lines, respectively. Studies on the subcellular distribution of these enzyme activities showed that the activity measured with acetaldehyde and NAD (ACA/NAD) was almost equally distributed between the cytosol and the subcellular particles in the three cell populations, but the ACA/NADP activity was shifted towards the cytosolic compartment in hepatomas, especially in HTC cells. The BA/NAD and BA/NADP ALDH activities found in the organelles of hepatoma cells were markedly reduced in comparison with hepatocytes, in favour of the cytosol. The most striking difference between the normal and the transformed cells was the 94-fold increase over hepatocytes of the BA/NADP activity, found in the cytosolic fractions of HTC cells. MH1C1 cells showed a less pronounced (7.5-fold) enhancement of this tumour-associated specific activity.(ABSTRACT TRUNCATED AT 250 WORDS)

The ability of mineral dusts and fibres to initiate lipid peroxidation. Part II: relationship to different particle-induced pathological effects

“…40 Hence, cells with decreased ability to metabolise lipid peroxidation products were found to be more sensitive to the cytotoxic effects of these products. 41 The majority of the aforementioned metabolic investigations were conducted in various cell and tissue types: hepatocytes and hepatoma cells; 41,42 isolated perfused rat hearts; 43 enterocytes of rat small intestine; 44 Ehrlich ascites tumour cells; 40 and kidney. 45 It is worthwhile considering some of the enzymes in these cell and tissue types in more detail, primarily to compare the response for those enzymes studied in the lung following mineral dust and fibre exposure.…”