Paraplegia differentially increases arterial blood pressure related cardiovascular disease risk factors in normotensive and hypertensive rats

Abstract

Older individuals (>50 years of age) are increasingly sustaining spinal cord injuries (SCI) and often have pre-existing medical conditions, including hypertension. Furthermore, the life expectancy of individuals with paraplegia has increased to near that of able-bodied individuals. Thus, chronic diseases associated with aging (e.g. hypertension) are increasing in this population. We tested the hypothesis that paraplegia differentially increases blood pressure related cardiovascular disease (BP-CVD) risk factors in normotensive (Wistar Kyoto rat, WKY) and spontaneously hypertensive rats (SHR). To test this hypothesis, intact and paraplegic SHR and WKY rats were chronically instrumented for recording BP-CVD risk factors over 7 weeks. Paraplegia in both the SHR and WKY rats increased heart rates (27 and 22% in SHR and WKY, respectively), heart rate loads (425 and 323% in SHR and WKY, respectively), the standard deviation of systolic (15 and 23% in SHR and WKY, respectively) and diastolic blood pressure (15 and 13% in SHR and WKY, respectively) and reduced activity (−70 and −57% in SHR and WKY, respectively). Paraplegia in the WKY rats reduced systolic (−4%) and diastolic (−5%) blood pressures while systolic and diastolic loads were not significantly different. In sharp contrast, paraplegia in the SHR increased systolic (6%) and diastolic (5%) blood pressures as well as systolic (41%) and diastolic loads (9%). These data demonstrate that paraplegia increased BP-CVD risk factors in normotensive and hypertensive rats. Importantly, the impact of paraplegia on BP-CVD risk factors was greater in the SHR.