Regulation of glomerular volume in normal and partially nephrectomized rats

Glomerular extracellular matrix accumulation may derive from the stretching of mesangial cells caused by excessive glomerular dilatation. The relationship of glomerular volume (V-G) to intraglomerular pressure, expressed as compliance or as mean V-G in the isolated, perfused rat glomerulus, was used to analyze factors that regulate V-G. Glomeruli were highly distensible over the normal and relevant abnormal range of pressure. Compliance increased directly with basal V-G (P < 0.001), i.e., larger glomeruli dilated more than smaller ones at any given pressure. Perfusion with atrial natriuretic peptide did not alter compliance, and inhibitors of nitric oxide synthesis exerted only a trivial effect. V-G expansion was consistently reduced by angiotensin II, but this effect was small (3.8%, P < 0.001). After subtotal nephrectomy, compliance increased by 59% in the remnant glomeruli (P < 0.001); 22% of this increase was attributable to structural changes, and the remainder was attributable to the large basal V-G of the hypertrophied glomeruli. Thus the major determinants of V-G expansion include capillary wall tension, basal V-G, and intrinsic distensibility, which is markedly influenced by the character of the extracellular matrix and only slightly altered by an angiotensin II-modified mesangial cell tone.