PS-B02-12: EFFECTS OF ULTRAVIOLET LIGHT ON BLOOD PRESSURE AND LEFT VENTRICULAR FUNCTION

Abstract

Ultraviolet light (UV), induces the activation of constitutive nitric oxide synthases, which produces nitric oxide (NO) of vascular relaxation factor. We hypothesize that UV-induced production of NO could have beneficial effect on hypertension. Twelve 6-week-old salt-sensitive hypertensive rats (Dahl-Iwai salt-sensitive DIS/Eis, Japan Society for the Study of Hypertension, Shizuoka, Japan) were used in this study. These rats were fed a high-salt diet containing 8%NaCl until 10 weeks of age and were then randomly divided into three groups i.e. baseline group (group non-UV), 0 h post UV (group UV 0 h), and 6 h post UV (group UV 6 h). The rats were irradiated with UVA and UVB lamps at an intensity of 100 mJ/cm2. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured by using tail-cuff method (BP-98A; Softron Co., Ltd., Tokyo, Japan). We evaluated left ventricular (LV) systolic and diastolic function using echocardiography with a 12 MHz transducer connected to a Xario ultrasound system (Toshiba Medical Systems Co., Tochigi, Japan). Interventricular septal thickness, LV posterior wall thickness, and LV end-diastolic and end-systolic diameters (LVDd and LVDs) were obtained from a short-axis view. Percent LV fractional shortening (%LVFS) was calculated as an index of LV systolic function. Peak flow velocities at the mitral level during rapid filling (E) and deceleration time (Dct), and peak early diastolic mitral annular velocity which indicate LV diastolic function, were measured using pulsed and tissue Doppler echocardiography. Histological skin tissue sections were fixed with 4% paraformaldehyde phosphate buffer solution for 24 h at room temperature, embedded in paraffin, sectioned transversely (thickness, 3 μm), and stained with hematoxylin-eosin to evaluate the impairments of skin. The SBP and DBP were lower in group UV 6 h than group non-UV and group UV 0 h. In contrast, there were no significant differences in heart rate and body weight among the three groups. The peak early diastolic mitral annular velocity was greater in group UV 6 h than group non-UV and group UV 0 h. LVDd, LVDs, and %LVFS were not significantly different among the three groups. We did not find the impairments in skin after UV irradiation. UVA and UVB may play an important role in regulating not only blood pressure but also LV function.