This article is more than 5 years old. Information may no longer be current.

UVA irradiation decreased blood pressure in healthy participants

Healthy volunteers experienced blood pressure decreases during ultraviolet A irradiation that may be driven in part by mobilizing cutaneous nitric oxide stores, according to recent study results.

“We have identified a vitamin D-independent mechanism by which sunlight can lower blood pressure,” researcher Richard B. Weller, MD, FRCP(Ed), senior lecturer in dermatology, University of Edinburgh, told Healio.com.

 

Richard B. Weller

Weller and colleagues studied 24 healthy volunteers (aged 22 years; 18 men) who were randomly assigned to a low nitrite/nitrate diet (n=12) or an unrestricted diet (n=12) 2 days before ultraviolet A (UVA) irradiation.

The low-nitrite/nitrate group participated in a follow-up study 1 week later in which 500 mg potassium nitrate was ingested. They then were sham irradiated for 22 minutes after being covered in a metal foil “space blanket” that allowed lamp-induced temperature rise but prevented UVA from reaching the skin. After a 60-minute observation, the participants underwent active UVA irradiation of 20 J/cm2 for 22 minutes and observed for another 60 minutes. Blood pressure (BP), heart rate, core temperature and surface temperature were measured. Blood was drawn and stored to later determine nitric oxide (NO) metabolites.

Also conducted was a study of 12 healthy men (aged 22 years) who received cannulation of the nondominant brachial artery. At separate times, they received sham or active UVA irradiation of the cannulated forearm.

Irradiation with two standard erythermal doses of UVA lowered diastolic blood pressure (DBP) in the 24 participants by 4.9 ± 0.7 mm Hg for 30 minutes, with greater changes during active vs. sham irradiation (P=.0071). No significant changes were noted in systolic BP. This was accompanied by concomitant decreases in circulating nitrate and rises in nitrate concentrations.

Dietary intervention “had no effect on UV-induced hemodynamic changes, indicating that cardiovascular effects were not mediated via direct utilization of circulating nitrate,” the investigators said.

In the cannulation forearm study, UVA irradiation caused increased blood flow independently of NO-synthase activity, suggesting involvement from preformed cutaneous NO stores.

“Collectively, our data provide mechanistic insights into an important function of the skin in modulating systemic NO bioavailability which may account for the latitudinal and seasonal variations of BP and cardiovascular disease,” the researchers concluded.

Disclosure: The researchers report no relevant financial disclosures.