Glomerular Distensibility

How intraglomerular hypertension may induce hemodynamic strain and trigger a cascade of metabolic events has been clarified following the demonstration of the unique elastic properties of the glomerular structure and the response of mesangial cells when subjected to mechanical stretch in tissue culture. Conclusive evidence of glomerular elasticity has been provided by studies in isolated microperfused glomeruli ex vivo [20]. As the intraglomerular pressure is increased from zero to levels approximating those observed in the diabetic and in the remnant kidney, glomerular volume increases by about 30% [32]. In addition, due to the high elasticity of the glomerular structure, volume changes reach their maximum within 3-4 seconds following alteration in intraglomerular pressure [19]. This elasticity, therefore, allows the occurrence of significant volume changes even with the most transient variations in intraglomerular pressure. Further, for the same increase in internal pressure, the degree of distention of the hypertrophied diabetic glomeruli is significantly greater than that in normal sized ones [33].

Glomerular expansion is, obviously, associated with the stretching of its structural components, including the extracellular matrix and the cellular constituents. Because both capillary lumina and mesangial regions equally participate in the overall increase in glomerular volume [19], endothelial, mesangial and epithelial cells will all be subjected to stretch as intraglomerular pressure increases. Due to the central location of the mesangial regions within the glomerular lobule, mesangial cells (MC), in particular, experience substantial mechanical strain. Detailed morphological studies have demonstrated how numerous cytoplasmic projections emerging from the MC body extend between adjacent capillaries and firmly attach to the perimesangeal regions of the glomerular basement membrane [34]. Therefore, the centrifugal displacement of these regions during glomerular expansion is expected to result in marked tridimensional MC stretch.

In addition to MC, podocytes are also expected to be subjected to intense mechanical strain during glomerular distention. Since these cells are commonly attached to several capillaries via their extended foot processes, capillary dilation will result in their bi-dimensional stretch extending over a wide surface [35].

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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