Enzymatic hydrolysis of luminal coronary glycosidic structures uncovers their role in sensing coronary flow

Endothelial luminal glycocalyx (ELG) is a multifunctional complex structure made off of a diversity of glycosilated proteins, and glycosaminoglycans (GAG). Coronary ELG may participate as a sensor of coronary flow (CF) to induce inotropic and dromotropic effects. In isolated perfused guinea pig heart we tested the role of glycosidic groups of glycans bound to proteins and GAG of the ELG on CF-induced inotropic and dromotropic effects. To study the role of saccharide related groups of certain glycans, they were removed by selective enzyme hydrolysis or bound to a selective plant lectin. CF-induced positive inotropic and positive dromotropic control curves were obtained and the effects of intracoronary infusion of enzyme or lectin determined. The analyzed groups were as follow: 1) Fucosidase enzyme and Ulex europeasus lectin; hydrolysis and binding respectively (H&Br) to alpha-linked fucosyl related groups. 2). Endoglycanase-H and Lycopersicon esculentum (H&Br to N-linked beta-1,3GlcNAc related groups). 3) O-glycanase and Arachis hypogea (H&Br to O-linked beta-Gal1, 3GalNac related groups). 4) Sialidase and Maackia amurensis (H&Br to neuraminic acid related groups). In treatments 1-3 both. lectin and corresponding enzyme, equally depressed CF-positive dromotropic effects without affecting positive inotropic effects. In treatment 4 both lectin and enzyme equally depressed CF-positive inotropic effects without dromotropic effects. The differential role of GAG hyaluran or heparan groups on CF-positive inotropism and positive dromotropism respectively was shown. Infusing hyaluranidase removed hyaluran that solely inhibited CF- inotropism while removal of heparan with heparinase solely inhibited CF-dromotropism. Only the effects of hyaluronidase were reversed infusing hyaluronidate. Our results indicate glycans of ELG are elements of complex multimolecular sensors of coronary flow.