Reticuloendothelial Clearance of Blood-borne Particulates

Abstract

The rapid increase in sheep lung vascular permeability observed during Pseudomonas aeruginosa bacteremia may be due to embolization of the pulmonary microvasculature by blood-borne particulates. Since alterations in lung microvascular permeability during mild septicemia in sheep may reflect inefficient RES phagocytic clearance of bacteria as well as products of bacterial induced intravascular coagulation, the opsonic and phagocytic aspects of RES function in sheep (30–50 kg) were compared to other species. RES function was evaluated by both the clearance and relative organ uptake of gelatinized I¹³¹ RE test lipid emulsion and gelatinized colloidal carbon. Immunoreactive opsonic ₂SB glycoprotein levels were determined by electroimmunoassay. The phagocytic index for RES clearance of the gelatinized (500 mg/kg) test lipid in sheep was 0.019 ± 0.002 corresponding to a half-time of 16.65 ± 1.74 minutes. With colloidal carbon (64 mg/kg), the phagocytic index in sheep was 0.080 ± 0.026, corresponding to a half-time of 6.16 ± 1.99 minutes. The per cent of injected lipid emulsion (%ID) in major RE organs, on a total organ basis (TO), was: liver = 15.69 ± 1.65%; spleen = 2.09 ± 0.78%. Localization in the lung = 31.39 ± 6.2%. The per cent of carbon localized in major RE organs (%ID/TO) was: liver = 21.37 ± 1.9%; spleen = 1.95 ± 0.55%. Localization in the lung = 32.70 ± 4.55%. In contrast, clearance and organ distribution of the blood-borne test microparticles in rats and dogs at the same relative challenging dose revealed a much more intense and rapid liver and spleen RES uptake with minimal lung localization (1–2%). Immunoreactive opsonic protein concentrations varied greatly with species and directly correlated with efficiency of RES function. Levels observed were: dog = 1285