Fructose metabolism in the liver

Abstract

An investigation of the metabolism of fructose by rat liver has been carried out with particular reference to control by sex hormones and the possible relationship in humans between dietary sucrose, blood triglycerides and heart disease.

The incorporation of label from 14C-fructose and 14C-glucose into liver triglycerides has been studied: the formersugar was observed to produce the greater incorporation.

Fructokinase activity in liver tissues from male andfemale animals at various stages of development has beenmeasured and sex and age differences were noted. Testosteroneinjections elevated the level of fructokinase activity in maleand female rats and produced similar effects with liver slices. Estrone, however, lowered the activity of the enzyme in maleanimals and increased it in females. The mode of action of testosterone has been investigated.

Fructose phosphate aldolase activity is higher in liverfrom male rats than from females and this may be related to the relatively rapid transfer of label from 14C-fructose to trioses when the ketose is incubated with male liver extracts. Testosterone injections produce no change in the levels of the aldolase.

Some related, preliminary work on the purification of liver fructokinase and the analysis of glyceride fatty acids from various rat tissues is also described.