Nitric oxide-mediated vasodilation in tibial bone in young healthy individuals

Despite the critical importance of sufficient and well-regulated blood flow supply for bone health, regulation of bone blood flow in humans remains poorly understood. We have recently shown that sympathetic and myogenic control have active roles in regulating blood flow to tibial bone in humans. Responses are smaller and delayed in the tibia compared to the whole leg, underscoring the importance of directly interrogating mechanisms underlying bone blood flow control. Nitric oxide (NO) mediated vasodilation is another important regulatory mechanism and studies to date have been confined to assessment of whole limb blood flow responses that primarily reflect muscle. In young healthy individuals (N=8), we characterized NO-mediated vasodilation in tibial blood flow and contrasted it to whole leg blood flow. We employed sublingual nitroglycerin (0.4 mg) as an NO donor. We obtained a 5 min resting baseline, followed by the responses to sublingual nitroglycerin for 10 min in supine subjects. Tibial blood flow was measured continuously via near infrared spectroscopy as total hemoglobin (Hb) and whole leg blood flow as popliteal Doppler flow velocity in the same leg. NO-mediated vasodilation was characterized by peak response, time to peak response, and time to return to baseline over the 10 min response. Tibial blood flow (total Hb) increased rapidly in response to nitroglycerin reaching a maximum of 1.61 ± 0.69 μM after 3.5 min. Afterwards, total Hb steadily declined, returning to baseline values by 10 min. Whole leg blood flow increased at a slower rate reaching a maximum of 7.12 ± 2.72 cm/s after 4.5 min. However, whole leg blood flow remained elevated throughout the entire 10 min measurement. Our results indicate that similar to other vascular beds, bone vasculature has a robust NO-mediated vasodilation, but appears to be faster and shorter lasting compared to the whole leg vasculature. This is not dissimilar from our previous findings indicating different time characteristic time-courses of response to other vascular controllers in tibial bone compared with whole leg vasculature. Paralyzed Veterans of America Research Foundation (AED), NIH NIAMS R21 AR074054 (JAT) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.