Dexamethasone‐Induced Effects on Autonomic Balance, Arterial Stiffness and Cardiac Remodeling in Sedentary and Trained Spontaneously Hypertensive Rats

Abstract

Dexamethasone (DEX)‐induced hypertension (HT) is associated with autonomic unbalance, increased arterial stiffness, reduced baroreflex gain and cardiac remodeling. Since hypertensive individuals may undergo DEX clinical treatment, it is reasonable to think that DEX treatment would exacerbate their arterial pressure, which, in turn, could culminate in a drastic increase on morbi‐mortality risk. Inversely, aerobic (AT) or combined (CT) training have been recommended for HT treatment and we have previously shown the preventive role of exercise training in counteracting DEX‐induced HT. Since nothing is known about the effects of DEX treatment in hypertensive rats, the aim of this study was to investigate if aerobic or combined training, performed before DEX treatment, would modulate autonomic balance, arterial stiffness and cardiac remodeling in spontaneously hypertensive rats (SHR) treated with DEX. Two groups of SHR (200g) underwent aerobic (AT) or combined (CT) training (60% of maximal capacity) for 8 weeks or were kept sedentary and then were treated with DEX (50μg /kg per day, s.c.) or saline (14 days). Wistar rats were used as normotensive control. Transthoracic echocardiogram and pulse wave velocity (PWV) were performed at the end of the protocol. Then, all rats underwent carotid artery catheterization for arterial pressure (AP) measurement and spectral analysis. Left ventricule (LV) was collected, weighed, and used for morphometric analysis. SHR had higher AP, PWV, LV weight, LV mass index (LVMI) and reduced systolic and diastolic function compared with wistar rats. DEX treatment (SD) did not aggravate mean AP (176±11 vs 184±8 mmHg) vs sed SHR (SC), but increased PWV (+17%). In addition, DEX did not alter the ratio between low frequency and high frequency bands of spectral analysis. DEX treatment increased LV diastolic diameter (LVDD/bw,+14%) compared with SC, but significantly decreased isovolumetric relaxation time IVRT (ms, −11%) and collagen density (−21%). Trained groups presented lower values of MAP (−18% and −13%, for AT and CT, respectively, vs SD). PWV was attenuated only by CT (−17%). Autonomic balance was not improved by training in SHR. Improved diastolic function and % of collagen (p<0.06) were observed in TD group only after AT. In conclusion, DEX treatment did not aggravate hypertension and its mechanisms in SHR, which suggests that hypertensive individuals may undergo DEX clinical treatment. Also, exercise training is a good strategy to decrease AP and improve cardiac remodeling in DEX‐treated SHR.Support or Funding InformationFunding: FAPESPThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.