Physiological Changes During Ischemia-Reperfusion Indicating Myocardial Damage Induced by Chronic and Excessive...

Ingestion of Hibiscus sabdariffa L. (HSL) provides antioxidants with beneficial effects for several pathologies with underlying oxidative stress. However, excessive, chronic consumption of the antioxidant-rich diet with HSL in healthy rats may possibly induce reductive stress (RS) with damaging effects. The aim of this study was to evaluate if the consumption of an infusion of 6% HSL for two months alters the function and structure of the myocardium. A total of 24 male Wistar rats were divided into three groups: Control (C), HSL infusion at 6% for two months (HSL 6%), and a washout group that received HSL 6% for two months followed by two months of natural water (HSL ± 6%). Myocardial performance during ischemia-reperfusion (I/R) was evaluated by using the isolated Langendorff heart model, accompanied by surface electrocardiography and histopathological analyses. Chronic 6% HSL intake increased systolic pressure (p ≤ 0.03), NrF2 expression, and elevated coronary vascular resistance, while it depressed mechanical performance and led to bradycardia and critical, extended asystolic/sinus pauses. Histopathology showed dense, permanent networks of interstitial and perivascular collagen encapsulating the hypertrophied cardiomyocytes. Chronic 6% HSL infusion was associated with myocardial structural, mechanical, and hemodynamic alterations, and with electrical changes during I/R. The washout group showed possible partial functional differences associated with withdrawal, although interpretation is limited by the longer study period.