[Animal experiment studies on parenteral utilization of maltose]

The utilisation of parenterally administered maltose was investigated in the anaesthetized rat, and in rats fixed in metabolic cages. Additionally, the metabolism of maltose was measured with the isolated perfused rat liver. During intravenous infusion of 0.3 g, 0.6 g or 1.2 g maltose (corresponding to 0.9 g, 1.8 g or 3.6 g/kg bodyweight) per hour a steady-state for maltose in blood was attained. Blood glucose concentration rose during the maltose infusions. The utilisation of parenterally administered maltose was established by a high rate of glycogen storage in the liver and by a decrease in concentration of free fatty acids in serum. During the 72 hour infusion of maltose at a rate of 0.23 g/hour (corresponding to 0.70 g/kg bodyweight) a constant blood maltose concentration of 60 mg/100 ml was measured. Simultaneously, the blood glucose concentration increased. The excretion of maltose and of glucose was approximately 5% of the total amount administered intravenously. The nitrogen sparing effect of maltose was equal to that of glucose (or glucose substitutes). In the streptozotocindiabetic rats, the renal excretion of maltose and glucose was 20-30% of the total amount. Moreover, blood glucose concentration was elevated significantly during maltose infusion. In the isolated perfused rat liver maltose hydrolysis was established. However, the glucose obtained by this hydrolysis was not metabolized by the isolated organ as was observed for glucose. On the other hand, the glucose substitutes (fructose, xylitol, sorbitol) are also partially transformed to glucose by the isolated liver. These substances, however, were additionally utilized by this organ in other ways. On the basis of these results it is concluded that maltose is metabolized following its intravenous application. Therefore, maltose should have advantages compared to glucose because of the lower osmotic pressure. The metabolism of maltose, however, is similar to that of glucose. The advantages of the glucose substitutes (fructose, sorbitol, xylitol) are not shared by maltose.