AGE-DEPENDENT CHANGES IN CARDIOVASCULAR AND METABOLIC RESPONSES TO EXERCISE IN BEAGLE DOGS

There is little data available on age-dependent changes in cardiovascu lar and metabolic functional capacity in older dogs and their geriatri c importance, although the frequency of cardiovascular diseases increa ses with age in the dog, too. Thus we investigated major cardiovascula r and metabolic parameters during and after physical exercise by tread mill-running in 5-10-year-old Beagles. We analysed electrocardiograms, body temperature, haematology, blood chemistry and blood gases. There were hardly any significant differences in the baseline values at res t in the younger dogs as compared with the older ones. However, in man y of these parameters, significant differences became manifest after e xercise. In the younger animals we measured significantly higher value s of haematocrit, red blood cell count and haemoglobin concentration a fter exercise by treadmill running. Furthermore, we also found a signi ficantly lower venous oxygen tension and lower oxygen saturation in ve nous blood as well as a significant lower plasma glucose level in the older animals during the recovery period. Heart rate during and immedi ately after exercise, as well as body temperature after exercise, was significantly lower in the older animals. Almost all of our examined p arameters that change significantly with age during and after exercise (e.g. heart rate, plasma glucose, body temperature and red blood cell s) are modulated at least partly by catecholamines and the sympathetic system. We were able to demonstrate in our investigation that the age ing of the cardiovascular system also results in a progressive loss of organ reserve and adaptability, presumably due at least in pare to fu nctional changes in the catecholaminergic system. This age-related dec line in the functional capability of the cardiovascular system probabl y creates a basis for cardiovascular diseases in older age.