How oxygen (O2 ) supply to capillaries is regulated to match the tissue's demand is unknown. Erythrocytes have been proposed as sensors in this regulatory mechanism since they release ATP, a vasodilator, in an oxygen saturation (SO2 )-dependent manner. ATP causes hyperpolarization of endothelial cells resulting in conducted vasodilation to arterioles.
Objective: We propose individual capillary units can regulate their own O2 supply by direct communication to upstream arterioles via electrically coupled endothelium.
Methods: To test this hypothesis, we developed a transparent micro-exchange device for localized O2 exchange with surface capillaries of intact tissue. The device was fabricated with an O2 permeable micro-outlet 0.2 × 1.0 mm. Experiments were performed on rat extensor digitorum longus (EDL) muscle using dual wavelength video microscopy to measure capillary hemodynamics and erythrocyte SO2 . Responses to local O2 perturbations were measured with only capillaries positioned over the micro-outlet.
Results: Step changes in the gas mixture %O2 caused physiological changes in erythrocyte SO2 , and appropriate changes in flow to offset the O2 challenge if at least 3-4 capillaries were stimulated.
Conclusion: These results support our hypothesis that individual capillary units play a role in regulating their erythrocyte supply in response to a changing O2 environment.
Keywords: capillary; in vivo; microvascular oxygen supply regulation; skeletal muscle; video microscopy.
© 2021 John Wiley & Sons Ltd.