title: Role of mesangial cell contraction in adaptation of the glomerular tuft to changes in extracellular volume.
abstract: Different chronic states of mesangial cell contraction were induced by variation of extracellular volume in Munich-Wistar rats for 6 days to study the influence of mesangial cells on the geometry of the glomerular tuft. Stereological analysis of superficial glomeruli in volume-expanded rats (VE, treated with enalapril) and volume-reduced rats (VR, treated with indomethacin) revealed a glomerular tuft volume 28.7% smaller, and a capillary luminal volume 32% smaller in VR than in VE rats. The filtration area [defined as glomerular basement membrane (GBM) area facing fenestrated endothelium] was greatly reduced in VR rats (97 +/- 16 X 10(3) micron 2 vs 137 +/- 13 x 10(3) micron 2). The surface density (Sv) of the GBM was higher by approximately 10% in VR rats primarily due to the considerable increase in Sv of the perimesangial GBM subdivision (0.189 +/- 0.01 micron 2/micron 3 vs 0.153 +/- 0.01 micron 2/micron 3), indicating a higher degree of mesangial cell contraction in these animals. Our results suggest (1) that mesangial cell contraction plays a major role in the adaptation of the glomerular tuft to variations in extracellular volume; (2) that the relevance of mesangial cell contraction for the regulation of glomerular haemodynamics appears to be small; and (3) that the reduction in filtration area, although prominent, cannot fully account for the considerable decreases in the ultrafiltration coefficient observed by others in acute and chronic studies.
authors.affiliation: Institut für Anatomie und Zellbiologie, Universität Heidelberg, Federal Republic of Germany.
authors.forename: M
authors.initials: M
authors.lastname: Elger
authors.forename: T
authors.initials: T
authors.lastname: Sakai
authors.forename: W
authors.initials: W
authors.lastname: Kriz
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001485:Basement Membrane / Q000648:ultrastructure; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D005920:Glomerular Mesangium / Q000166:cytology* / Q000502:physiology; D007678:Kidney Glomerulus / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D010952:Plasma Substitutes / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D010952:Plasma Substitutes