Heparan sulphate and hyaluronic acid components of the glycocalyx do not play a role in flow-mediated dilation of the iliac in the anaesthetized pig.

The shear-stress sensor function of vascular glycocalyx heparan sulphate and hyaluronic acid was investigated in vivo by assessing flow-mediated dilation before and after their removal. Heparinase III exposure (100 mU·mL ^-1 for 20 min; n = 6) did not significantly affect flow-mediated dilation of the iliac, from 0.42 ± 0.08 mm (mean ± SEM) to 0.34 ± 0.07 mm after ( P = 0.12; paired Student's t test) for a statistically similar increase in shear stress; 18.24 ± 4.2 N·m ^-2 for the control and 15.8 ± 3.6 N·m ^-2 for the heparinase III experiment ( P = 0.18). Hyaluronidase exposure (0.14-1.4 mg·mL ^-1 for 20 min; n = 8) also did not significantly reduce flow-mediated dilation of the iliac, which averaged 0.39 ± 0.08 mm before and 0.38 ± 0.09 mm after ( P = 0.11) for a statistically similar increase in shear stress; 11.90 ± 3.20 N·m ^-2 for the control and 9.8 ± 3.33 N·m ^-2 for the hyaluronidase experiment ( P = 0.88). Removal of both heparan sulphate and hyaluronic acid was confirmed using immunohistochemistry. Neither the heparan sulphate nor the hyaluronic acid components of the glycocalyx mediate shear-stress-induced vasodilation in conduit arteries in vivo.