The primary aim of this proposal is to increase our understanding of the role and importance of acute and chronic exercise in the management of hypertension, a health risk that affects the lives of millions of Americans each year.
The specific aims are to evaluate the influences of moderate and heavy isometric and isotonic exercies on the life-span, incidence of strokes, and resting pressures in stroke-prone hypertensive rats; to develop a primate model to study the effects of isometric exercise on resting blood pressure; to determine whether the Oscai rat model for obesity will exhibit evidence for hypertension; to perfect a water treadmill for exercising rats; and to evaluate the hypothesis that either heavy isontonic or isometric exercise by genetic hypertensive and stroke-prone rats will cause a """"""""central disruption"""""""" that results in higher resting pressures. Associated with these aims are the concepts that moderate isotonic exercise by hypertensive rat populations 40-60% VO2max) will not have a """"""""cental disruptive effect""""""""; fore-limb hanging by rats is an effective isometric procedure; and the addition of weights to animals in a water tank is not physiologically desirable for swimming studies because of its submergence effects. Studies with the stroke-prone animals will include methods that allow us to quantify the exercise prescribed (VO2 while running, force when hanging) and its effects. Included within the latter category are resting blood pressure (tail cuff), resting cardiac output (thermal dilution), cerebral vessels wall/lumen ratios (perfusion), cerebral blood flows (microspheres), baroreceptor reflex responses (lower body negative pressure and Doppler flow probes), and myocardial capillarization (perfusion). Chemical sympathectomy and central injections of """"""""putative transmitters"""""""" will be used to determine changes in the functioning of the autonomic nervous system. The work previously conducted by Gisolfi with exercising primates will be expanded to include only isometric exercises (20% and 60% MVC) and their effects on resting blood pressure. The influences of increases and decreases in body weight on resting blood pressure will be followed in obese rats. Finally we intend to develop a unit that allows investigators to study the anatomical and physiological effects of swimming on rats without the trauma of repeated submergences and the consequences of the diving reflex.
