Cutaneous Microvascular Responses to Local Heating on Ventral and Dorsal Aspects of the Forearm

• Published in: The FASEB journal 2022-05, Vol.36 (S1), p.n/a
• Main Authors: Patik, Jordan C., Shoemaker, Leena N., Wenner, Megan M., Edwards, David G.
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.2022.36.S1.R6155

The cutaneous microvasculature is considered a representative vascular bed and is regularly used to interrogate the mechanisms of microvascular function in healthy and diseased humans. For instance, cutaneous dilation in response to local heating can provide an index of nitric oxide (NO) bioavailability. While the skin of the forearm is typically used for local heating studies, some studies have used the ventral forearm while others have used the dorsal forearm skin for this assessment. Since the dorsal aspect of the forearm typically has more hair and receives greater sun exposure than the ventral side, there is speculation that cutaneous dilation may differ from one side of the forearm to the other, in magnitude and/or mechanism. As such, studies utilizing different sides of the forearm may not be comparable. Therefore, we aimed to test the hypothesis that cutaneous local heating responses differ between the ventral and dorsal aspects of the forearm in response to the two most common temperature stimuli, 39°C and 42°C. Methods Ten young, normotensive individuals (6 men/4 women, age: 26 ± 2 years) were studied on two separate occasions separated by 2‐7 days. At each visit, 4 intradermal microdialysis fibers were placed in either the ventral or dorsal forearm, in a random order. Two fibers were perfused with Ringer’s solution to serve as control sites and the other 2 fibers were perfused with 10 mM N(G)‐Nitro‐L‐arginine methyl ester (L‐NAME) to inhibit NO synthase. Red blood cell flux (RBCF) was assessed at all sites via laser Doppler flowmetry. Each pair of sites (control and L‐NAME) was heated to either 39°C or 42°C for ~40‐45 min until RBCF plateaued. All sites were then infused with 28 mM sodium nitroprusside and heated to 43°C to establish maximal RBCF. Cutaneous vascular conductance (CVC) was calculated as RBCF / mean arterial pressure measured during the plateau and maximal phases. Plateau results are reported as a percentage of maximal CVC at each respective site. The relative NO contribution is reported as: [(control plateau – L‐NAME plateau)/control plateau] x 100. Results No differences were observed at the control site between ventral and dorsal aspects of the forearm when heated to 39°C (62 ± 13 vs. 62 ± 16 % CVCmax, P=0.99). Likewise, the heating response to 42°C was similar across the forearm (ventral: 90 ± 9 vs. dorsal: 86 ± 12% CVCmax, P=0.21). The relative contribution of NO to the plateau was comparable across the forearm at 39°C (ventra