Effect of prior nutritional status of the animal on the activity of lipogenic enzymes and the fatty acid content of cultured hepatocytes was investigated. Hepatocytes were isolated from rats that were starved for 24 h ('starved') or continuously fed ('fed'), or starved for 48 h and then re-fed for 48 h ('re-fed') with a carbohydrate-rich fat-free diet, and maintained as monolayer cultures for 96 h in a serum-free glucose-rich medium (Waymouth's MB752/1) supplemented with insulin, dexamethasone and tri-iodothyronine. The fatty acid content and the activities of acetyl-CoA carboxylase, fatty acid synthase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were determined initially at 3 h after plating and then every 24 h. Initially the activities of all the four enzymes were highest in hepatocytes isolated from the re-fed rats and lowest in those from the starved rats. With time in culture, the activity of all these enzymes increased severalfold (2-5, depending on the enzyme under consideration) in hepatocytes isolated from fed and starved rats, whereas there was a severalfold (2-5) decrease in the activity of these enzymes in hepatocytes isolated from re-fed rats. The initial fatty acid content of the hepatocytes from re-fed rats was 2-3 times that in the other two groups of hepatocytes. The fatty acid content seemed to increase in all three groups of hepatocytes during the 96 h in culture, but these apparent increases were not statistically significant.
The lipid concentration and fatty acid composition of the whole liver and of cultured hepatocytes isolated from the livers of rats fed ad libitum (fed), fasted for 24 hr (fasted), or fasted for 48 hr and then refed a fat-free, high carbohydrate diet for 48 hr (refed) was studied. Hepatocytes were maintained as monolayer cultures in serum-free, lipid-free media and their fatty acid composition was analyzed at 3, 24, 48, 72 and 96 hr. The livers of fed animals, as well as their hepatocytes, contained less total lipid than those from animals on either of the other dietary regimes. Livers of fasted animals had three times the amount of lipid found in the livers of fed animals, and the livers of refed animals contained five times the amount of lipid as the livers of fed animals (all based on mg lipid/g wet weight of liver). The fatty acid composition of hepatocytes after 3 hr of culturing was very similar to that of fresh liver when compared in each of the dietary regimes. However, while the fatty acid compositions of livers and hepatocytes from fed and fasted animals were similar, the pattern in liver of refed animals was quite distinct from that of the fed animals. In the fed and fasted animals palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1[n-9]), linoleic acid (18:2[n-6]) and arachidonic acid (20:4[n-6]) were the major fatty acids of the liver; in refed animals 16:0, palmitoleic acid (16:1[n-7]), 18:0, 18:1(n-9) and cis-vaccenic acid (the n-7 isomer of oleic acid) were the major fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)
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