The effects of aerobic conditioning on the development of atherosclerotic plaque in miniature swine

Abstract

Purpose. The purpose of this study was to investigate the effects of aerobic conditioning on the extent of atherosclerotic plaque formation in aortas of miniature swine fed a high fat/high cholesterol diet. Procedure. Twenty male miniature swine, ranging in age from 6 to 10 weeks were stratified by litter to a group fed an atherosclerotic diet and one group fed a standard commercial pig ration. During the first eight weeks of the study, the animals were fed an isocaloric diet in addition to being familiarized with treadmill running. Bi-weekly blood samples were collected and analyzed for total cholesterol, low density lipoproteins (LDL), high density lipoproteins (HDL), and triglycerides. At week nine all animals underwent a maximum graded exercise test (IGXT) using a protocol that was developed during preliminary studies. Following the IGXT each group was subdivided into an exercising and sedentary subgroup (atherosclerotic exercise (AE), atherosclerotic sedentary (AS) and a control exercise (CE) and control sedentary (CS) group). The two exercising groups (AE and CE) were submitted to a training regimen, consisting of four 30-minute training sessions per week at 75-85 percent of their maximum heart rate. This criterion had been established at the IGXT. During this period, the sedentary groups underwent "sham exercise" to ensure that handling and the accompanying stress was equal among all groups. The training heart rate was evaluated and adjusted once a week. At the end of the eight week training period all subjects underwent a second maximal graded exercise test (PGXT). Work was calculated as force X distance. Following the PGXT, all animals were anesthetized and then sacrificed by infusing 10% Buffered Formalin into the arterial system by means of a left ventricular stab at a pressure slightly exceeding the mean aortic pressure. The aorta was excised, cleaned and mounted on a solid background and consequently stained for plaque formation with Sudan IV stain. Quantitative measurements were made of the extent of atherosclerotic lesions from black and white photographic negatives and life-size colour prints of the stained specimen. Density as well as the area involved were considered in the quantitation. . . . (Author's abstract discontinued here because it exceeds stipulated maximum length.) UMI