Abstract
Adenosine-mediated recruitment of microvascular volume in heart and muscle has been suggested to include, in addition to vasodilation of resistance vessels, an increased accessibility of the endothelial glycocalyx for flowing plasma as a result of an impairment of its barrier properties. The aim of the current study was to investigate the effect of systemic intravenous administration of adenosine on the glycocalyx-dependent exclusion of circulating blood at a whole-body level. In anesthetized goats (N = 6), systemic blood-excluded glycocalyx volume was measured by comparing the intravascular distribution volume of the suggested glycocalyx accessible tracer dextrans with a molecular weight of 40 kDa (Dex-40) to that of circulating plasma, derived from the dilution of labeled red blood cells and large vessel hematocrit. Systemic glycocalyx volume was determined at baseline and during intravenous infusion of adenosine (157 ± 11.6 μg/kg min(-1)). Blood-inaccessible glycocalyx volume decreased from 458.1 ± 95.5 to 18.1 ± 62.2 mL (P < 0.01) during adenosine administration. While circulating plasma volume did not change significantly (617.1 ± 48.5 vs. 759.2 ± 47.9 mL, NS), the decrease in blood-excluded glycocalyx volume was associated with a decrease in Dex-40 distribution volume (from 1075.2 ± 71.0 to 777.3 ± 60.0 mL, P < 0.01). Intravenous administration of adenosine is associated with a robust impairment of whole-body glycocalyx barrier properties, reflected by a greatly reduced exclusion of circulating blood compared to small dextrans. The observed decrease in Dex-40 distribution volume suggests that the reduction in glycocalyx volume coincides with a reduction in tracer-accessible vascular volume.