Cellular mechanisms within the juxtaglomerular apparatus.
The tubular-vascular connection via the juxtaglomerular apparatus appears to serve two functions, local control of renal vascular resistance and regulation of renin secretion. A fall in single nephron glomerular filtration rate (SNGFR) and an increase in resistance are produced by an increase in NaCl concentration at the macular densa. This change also results in inhibition of secretion of renin. The macula densa has a unique location near the terminal end of the thick ascending limb, where NaCl concentration is highly flow dependent. The cellular mechanisms by which changes in tubular fluid NaCl produce vasoconstriction and inhibition of renin secretion are unknown, but the anatomy of the juxtaglomerular apparatus strongly suggests that such responses may be mediated by the extraglomerular mesangial cells located in the polar cushion underlying the macula densa. Recent evidence suggests that interstitial chloride concentration in this compartment may be quite variable, and that increases in external chloride may enhance the activation of the mesangial cell.
Department of Internal Medicine, University of Michigan, Ann Arbor 48109-0364.
J P
JP
Briggs
O
O
Skøtt
J
J
Schnermann
D005246:Feedback; D005919:Glomerular Filtration Rate; D005920:Glomerular Mesangium / Q000166:cytology / Q000502:physiology; D006801:Humans; D007606:Juxtaglomerular Apparatus / Q000166:cytology / Q000502:physiology*; D007672:Kidney Cortex / Q000098:blood supply / Q000166:cytology; D007684:Kidney Tubules / Q000166:cytology / Q000502:physiology*; D012083:Renin / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism
D012965:Sodium Chloride; D012083:Renin