Mahmoud, Said Abdel Fattah (1979)
Carbohydrate metabolising enzymes in male and female rats.
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It has been reported that the increase in the concentration of triglyceride in fasting serum is more likely to be induced by carbohydrates than by fats in the diet. This fact has focussed the attention of researchers on the possible role of dietary carbohydrates in the aetiology of ischaemic heart disease. Epidemiological studies have also shown that there is a positive correlation between the incidence of atherosclerosis and (1), the amount of sucrose in diet and (2), the level of triglyceride in the fasting serum. Moreover, some epidemiological studies suggest that the increase in the death rate from ischaemic heart disease coincides with the increased consumption of sucrose in western countries. Feeding sucrose has been reported to produce hypertriglyceri-daemia in man and experimental animals and this carbohydrate has a greater hypertriglyceridaemic effect than glucose or starch. Sucrose-or fructose-induced hypertriglyceridaemia is more marked in male animals than females. These facts when considered together, suggested that an examination of sex differences in the metabolism of sucrose might throw some light on the different incidence of ischaemic heart disease in men and women. Hence the activities of a number of liver enzymes involved in fructose metabolism have been examined using male and female rats on normal and carbohydrate-supplemented diets. Sex differences were observed in three cases: glycerol kinase, glycerol 3-phosphate dehydrogenase and sorbitol dehydrogenase but dietary factors modified or nullified these differences. The conclusion was reached that glycerol 3-phosphate might be produced more readily in female rats than males because aldolase and glycerol 3-phosphate dehydrogenase activities were higher in the females. The effect of sex hormones on the activity of glycerol kinase was examined using hepatocyte preparations. A rapid activation of this enzyme in cells from both male and female livers was observed when relatively high concentrations of dihydrotestosterone were used. Estradiol-17B had no effect. The activation was most marked with hepatocytes from castrated male rats and the phenomenon could only be demonstrated with intact cells. There was no evidence that the dihydrotestosterone effect was mediated through protein synthesis.
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Institution: University of London, Royal Holloway College (United Kingdom).