Improving Rana pipiens health status maintains capillary hydraulic conductivity (Lp) response to a change in shear stress (ΔSS)

Abstract

Infection may be a confounding factor in studies of individual capillaries in situ. Recently, we tested an anti-parasitic in combination with the standard antibiotic to improve frog health status. Since the relationship between ΔSS and Lp appears to be a sensitive index of healthy capillary function, the purpose of the present study was to test capillary responses to ΔSS in frogs treated with our standard care, gentamicin (G, 1.3mg·L−1; n=16) versus G plus levamisole HCl (L, 12mg.L−1; n=18). We hypothesized that capillaries would retain their ability to adjust Lp after a ΔSS with G/L treatment. Frog mesenteric true capillaries, without rolling or sticking WBC, were cannulated individually. Lp was assessed on the first occlusion using the modified Landis technique. Mean Lp was 6.7±1.5 x 10−7 for G and 3.5±0.4 x 10−7 cm.s−1.cmH2O−1for G/L (P=0.05). Regression analysis revealed more outlier values for Lp in G- (38%) versus G/L-treated (22%) frogs. A significant relationship between ΔSS and Lp existed for both groups with the slopes indistinguishable (G, 0.04±0.02, R2=0.49 vs G/L, 0.07±0.02, R2=0.44; P<0.04). Fewer outliers suggest that treatment with G/L improves the success rate of experiments by decreasing parasites as well as bacteria in the frog. The ability of individual capillaries to adjust to a range of changes in shear stress may be one characteristic of healthy barrier function. Improving the health status of Rana pipiens with G/L did not diminish capillary functional adjustment to ΔSS stimuli. Supported by NIH RO1 HL63125.