Evaluation of Glucose Absorption Level in the Small Intestine of Different Rat Strains under Natural Conditions

Abstract

The peculiarities of carbohydrate metabolism were studied in seven rat strains under conditions maximally approximating natural ones. The glucose absorption level in the small intestine was evaluated using a method based on ad libitum drinking of concentrated glucose solutions by prefasted (18–20 h) rats. It was shown that in the steady-state regime the volume-normalized uptake rate of glucose solution (mL/min) was constant and inversely proportional to the glucose concentration in the solution, while the uptake rate of glucose itself (μmol/min) was independent of the substrate concentration in quite a wide range, being mainly determined by the absorptive capacity of the small intestine. A significant difference was revealed between the tested rat strains in terms of the rate of glucose absorption from its solution (200 g/L). In the daytime (10 AM–4 PM), the highest rates were observed in Sprague Dawley rats (116.7 ± 3.1 μmol/min) while the lowest—in Wistar Kyoto rats (35.6 ± 1.1 μmol/min). In the evening (4–10 PM), rates of glucose absorption in different rat strains were 1.3–2.2 times higher than in the daytime. Apparently, the increased absorptive capacity of the small intestine in the evening is due to enhanced SGLT1-mediated active glucose transport and reflects the peculiarities of carbohydrate metabolism regulation in different rat strains.