Micromechanical aspects of mesangial cells of the kidney

With video microscopy and whole-cell patch-clamp recording techniques, the response of mesangial cells (MCs) of the rat kidney to the exposure of hypoosmotic media was investigated in the authors´ study. It was observed that, decreasing extracellular tonicity by increments as large as 40 mosM, whole-cell patched mesangial cells can maintain their volumes without lysis. A model for cell volume regulation was proposed, whereby MCs are both sensors and effecters of water balance in the glomerulus. To investigate the membrane elasticity of mesangial cells, positive pressures were applied to pre-swollen cells through micropipette. Changes in cell dimension were measured, and area expansion modulus of mesangial cells was calculated based on Hooke´s Law. The maximum fractional area expansion observed was 25%, which was much greater than the elastic limit reported (2-3%) for the bilayer. The estimated area expansion modulus was 230 dynes/cm for mesangial cells