Expression of human glucose transporter type 1 and rat hexokinase type II complementary DNAs in rainbow trout embryos: Effects on glucose metabolism

Sugars are utilized poorly in fish mainly because of low rates of transport across plasma membrane and phosphorylation. To evaluate whether it is poss ible to augment carbohydrate metabolism in fish using heterologous genes, e xpression of human glucose transporter type 1 (hGLUT1) and rat hexokinase t ype II (rHKII) complementary DNAs cloned with cytomegalovirus promoter was followed in rainbow trout embryos. Both genes were transcribed. Hexokinase activity, undetectable in control, was found in transformed blastulas. Incr eased rates of C-14-methylglucose uptake and sensitivity to cytochalasin B indicated the presence of facilitative hexose transport due to hGLUT1 expre ssion. Effect of hGLUT1 on production of (CO2)-C-14 from glucose was greate r than that of rHKII. Coexpression of the genes did not increase the rate o f glucose oxidation compared with expression of hGLUT1 alone.