Ultraviolet irradiation benefits left ventricular hypertrophy and mitochondrial morphology of cardiomyocytes in hypertensive rats.

Insufficient exposure to sunlight increases the risk of cardiovascular diseases. Hypertensive left ventricular (LV) hypertrophy exacerbates the risks of myocardial ischemia, ventricular arrhythmias, sudden cardiac death, and heart failure. This study aimed to determine the effects of ultraviolet (UV) irradiation on LV hypertrophy and mitochondrial morphology. Eighteen 7-week-old Dahl salt-sensitive (Dahl S) rats were categorized into three groups (n = 6 each) and fed sodium chloride (NaCl) diets, as follows: UV-irradiated [UVB+A (+), 8% NaCl], non-UV-irradiated [UV (-), 8% NaCl], and control [UV (-), 0.3% NaCl]. UV irradiation was administered at a low intensity of 100 mJ/cm² for 6 days per week. Echocardiography and mitochondrial analyses were performed to evaluate LV hypertrophy and cardiomyocytes, and skin tissues were stained with hematoxylin and eosin to assess the pathological abnormalities at 12 weeks of age. LV mass was significantly reduced in the UVB+A (+) and control groups compared to that in the UV (-) group. Mitochondrial structural abnormalities in cardiomyocytes were observed only in the UV (-) group, but not in the UVB+A (+) or control group. Pathological skin abnormalities were not observed in any of the three groups. These findings suggest the potential benefits of UV irradiation in hypertensive models.