The catalase activity of Apis mellifera L. upon summer feeding with varying carbohydrate diet

In summer, honey bees often do not obtain sufficient amounts of food in nature and require additional feeding. However, the physiological and biochemical consequences of the additional feeding still remain poorly understood. Especially little is known about the possible effects of feeding on the activity of antioxidative enzymes, e.g., catalase (CAT), which is responsible for the scavenging of hydrogen peroxide and, therefore, is involved in the cell protection against different kinds of stress. The aim of our study was to evaluate the effect of summer feeding with solutions of different carbohydrates on the activity of CAT in foraging bees. The experimental colonies received additional feeding with a 30% sugar solution during two months. Afterwards, these colonies were fed for 4 days with different carbohydrate solutions: the first group was fed with a 30% glucose solution, the second group with a 30% fructose solution, the third group received no feeding, while the fourth group (control) received a 30% sugar solution. After this, all experimental colonies received 30% sugar solution again. The activity of CAT was measured (i) before the beginning of different carbohydrate diets, (ii) after the end of different carbohydrate diets, and (iii) at the 8th day after the colonies were returned on the 30% sugar solution. The highest CAT activity was found in abdomen, and the lowest one was found in thorax demonstrating organ-specificity of CAT activity of foraging bees. Ceasing feeding with sugar reduced catalase activity in all experimental groups. Herein, the highest decrease of CAT activity was observed for the bees of the experimental group, which received additional fructose feeding, whereas the least decrease was found for the bees of group without supplemental feeding, which were eating their own honey. The strongest decrease of CAT activity was detected in the abdominal tissues in all experimental groups. The CAT activity returned to its previous level within a week after termination of the monocarbohydrate diet and return to the feeding with 30% sugar solution. Thus, the lowest values of catalase activity were found for the feeding with 30% fructose solution, and the highest ones for 30 % sugar solution. Our data indicate that the consumption of different carbohydrates and the subsequent metabolic changes may affect the redox balance in different body parts of honey bees.