kinematic viscosity of lung surfactant with added Amyloid- β peptide

Lung surfactant, is a highly surface-active lipo-protein complex found in the fluid lining the air-liquid interface of the alveolar surfaces that essential for normal breathing, alveolar stability and host defense system in the lungs. The viscosity of lung surfactant is dependent on its molecular composition, its microstructure, the interactions between components and the environmental conditions. Viscosity is believed to influence the rate, extent and uniformity of distribution of surfactant in the lungs. The addition of various polymers and polysaccharide to lung surfactants improves surface activity and kinematic viscosity. In this study, we have measured the viscosities of calf lung surfactant extract (CLSE) with and without the addition of amyloid-β 25-35 (Aβ) peptide. A lower value of viscosity allows a more uniform and rapid distribution of the instilled surfactant with less initial loss due to coating of the upper airways. Our results indicate that at specific surfactant concentrations, the addition of Aβ peptide decreased the viscosity. At a concentration of 5mg/mL and 37°C, the addition of Aβ peptide (1% w/v) lowered the viscosity of CLSE. Addition of Aβ peptide to CLSE caused effects on viscosity that depended on the concentration of surfactant. Aβ peptide decreased the viscosity of dilute CLSE at 37°C from around 1.3 to about 0.8 cSt.