ABSTRACT
The blood thinning properties of pentoxifylline have been attributed to its ability to increase the deformability of red blood cells and improve their rheological properties. To interpret and substantiate these observations a novel approach is taken by measuring the stiffness of individual red blood cells from healthy humans before and after subscription to pentoxifylline for nine days. Atomic force microscopy nanoindentation experiments reveal that the elastic modulus of the red blood cells decreased by 30%-40%, after pentoxifylline subscription. This decrease in elastic modulus is related to the ability of pentoxifylline to increase the production of ATP and lower Ca2+ concentrations in red blood cells. The present in vivo experiments provide a deeper understanding of the mode of action of pentoxifylline, and pave the way to using indentation in medicine. A further unique advantage of this study is that it was performed on healthy volunteers, rather than requiring in vitro incubation.
Subject(s)
Anticoagulants/pharmacology , Elastic Modulus/drug effects , Erythrocytes/drug effects , Pentoxifylline/pharmacology , Adenosine Triphosphate/metabolism , Animals , Calcium/metabolism , Erythrocytes/metabolism , Humans , RatsABSTRACT
The mechanical properties of collagenous tissues, such as tendon and ligaments, are of particular interest as they are found extensively in the human body. In the present study the transverse mechanical properties of collagen fibers are reported for the first time. The elastic modulus was found to be 63 ± 4 MPa, while the viscosity was estimated to be 14 GPa ≤ η ≤ 56 GPa s. Comparison with similar data in the literature, for bulk tendon and collagen fibrils, suggests that the apparent modulus of a network of interconnected building blocks is reduced as compared to the modulus of the individual building blocks; in particular E (tendon) < E (fiber) < E (fibril); this is due to the fact that as the scale of the microstructure increases (i) slippage and sliding between the respective building blocks (fibrils or fibers) increases, (ii) the volume fraction of the stiff collagen proteins decreases.
