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Acta Physiologica (Oxford, England) May 2012
Topics: Humans; Juxtaglomerular Apparatus
PubMed: 22463607
DOI: 10.1111/j.1748-1716.2012.02429.x -
The American Journal of Physiology Nov 1979The juxtaglomerular apparatus, located in the glomerular hilum, consists of a vascular component (afferent and efferent arterioles and extraglomerular mesangium) and a... (Review)
Review
The juxtaglomerular apparatus, located in the glomerular hilum, consists of a vascular component (afferent and efferent arterioles and extraglomerular mesangium) and a tubular component (macula densa). Two types of contact between vascular and tubular components are observed: a) a complex type, involving distal tubule, extraglomerular mesangium, and proximal efferent arteriole, and b) a simple type, consisting of apposition of the basement membranes of the vascular and tubular components. Juxtaglomerular granular cells, the source of renin, are present throughout the vascular component but are more numerous in the afferent arteriole. They can be considered as "myoendocrine" cells, since they contain myofibrils and attachment bodies, together with secretory granules and crystalline protogranules. Macula densa cells differ from those elsewhere in the distal tubule in that their nuclei are closer to each other, the Golgi apparatus is basally located, and their basal membrane infoldings are less prominent. Adrenergic nerves are demonstrable by fluorescence histochemistry in the juxtaglomerular region. Electron microscopy reveals unmyelinated nerve fibers containing small dense-cored vesicles and capable, as shown by ultrastructural autoradiography, of incorporating exogenous tritiated norepinephrine. Neuroeffector junctions occur between nerves and cells of the vascular and, less frequently, the tubular component. In addition, adrenergic axons are observed in a juxtaglomerular cell tumor. Nerve terminals are seen in direct contact with the tumor cells.
Topics: Acetylcholinesterase; Animals; Arterioles; Axons; Cytoplasmic Granules; Humans; Juxtaglomerular Apparatus; Kidney Neoplasms; Kidney Tubules; Myofibrils; Nerve Fibers; Norepinephrine
PubMed: 386808
DOI: 10.1152/ajprenal.1979.237.5.F333 -
Advances in Nephrology From the Necker... 2000
Review
Topics: Animals; Juxtaglomerular Apparatus; Nitric Oxide; Nitric Oxide Synthase; Signal Transduction
PubMed: 11068637
DOI: No ID Found -
Current Opinion in Nephrology and... Jan 2005Monitoring interactions between dissimilar cells is a key to understanding the function of the juxtaglomerular apparatus. This review will summarize new findings on... (Review)
Review
PURPOSE OF REVIEW
Monitoring interactions between dissimilar cells is a key to understanding the function of the juxtaglomerular apparatus. This review will summarize new findings on tubuloglomerular feedback-mediated reductions in the glomerular filtration rate and renin release signals to elucidate how current research can benefit from visual approaches.
RECENT FINDINGS
Macula densa cells are capable of producing significant changes in cell volume depending on the rate of entry of salt through their apical membrane. Tubuloglomerular feedback activation by increased tubular salt content is associated with macula densa cell swelling and the simultaneous contraction of the terminal, intraglomerular, renin-positive segment of the afferent arteriole and the intraglomerular mesangium. Macula densa cells release adenosine triphosphate, which causes tubuloglomerular feedback-mediated vasoconstriction either directly through purinergic signaling or indirectly through its hydrolysis to adenosine. During conditions of low extracellular fluid volume, reduced tubular salt delivery causes macula densa cells to synthesize and release prostaglandin E2, which in turn stimulates the proliferation of juxtaglomerular cells, the synthesis and release of renin, and activation of the renin-angiotensin system. Renin release from juxtaglomerular cells represents a unique form of exocytosis: even large granules can release their content very rapidly without any significant movement relative to the juxtaglomerular cell membrane.
SUMMARY
A trend in biomedical research is to re-visit earlier studies using state-of-the-art experimental techniques. Imaging methods including the newest innovations in confocal fluorescence microscopy provide direct, visual information on juxtaglomerular apparatus function, with exceptional time and spatial resolution at the level of individual cells and organelles.
Topics: Humans; Juxtaglomerular Apparatus; Microscopy, Confocal; Microscopy, Fluorescence
PubMed: 15586016
DOI: 10.1097/00041552-200501000-00009 -
American Journal of Physiology. Renal... May 2009The juxtaglomerular apparatus (JGA) is a specialized contact region between the glomerulus and the cortical thick ascending limb that plays an active role in the... (Review)
Review
The juxtaglomerular apparatus (JGA) is a specialized contact region between the glomerulus and the cortical thick ascending limb that plays an active role in the maintenance of ion homeostasis and control of blood pressure. The JGA accommodates several different cell types, including vascular smooth muscle cells, endothelial cells, mesangial cells, macula densa cells, and renin-secreting juxtaglomerular granular cells. These cells, with the exception of the macular densa cells, are tightly coupled by gap junctions. Gap junction-mediated intercellular communication in the JGA provides a pathway for signal transduction and coordination of multicellular functions. Disruption of cell-to-cell communication in the JGA results in altered preglomerular vascular tone and renin secretion. This review summarizes recent data about the roles of gap junctions in the JGA and illustrates how gap junction-mediated intercellular Ca(2+) signals determine physiological responses in the JGA.
Topics: Animals; Calcium Signaling; Cell Communication; Gap Junctions; Humans; Juxtaglomerular Apparatus
PubMed: 19073638
DOI: 10.1152/ajprenal.90612.2008 -
Medicina 1969
Review
Topics: Animals; Anura; Chymosin; Dogs; Haplorhini; Humans; Juxtaglomerular Apparatus; Kidney Glomerulus; Mice; Rabbits; Rats; Species Specificity
PubMed: 4978537
DOI: No ID Found -
Kidney International Jun 1996The juxtaglomerular apparatus is an anatomic structure which links the distal end of the thick ascending limb at the macula densa with the glomerular vascular pole.... (Review)
Review
The juxtaglomerular apparatus is an anatomic structure which links the distal end of the thick ascending limb at the macula densa with the glomerular vascular pole. Specialized interstital cells and renin containing granular cells are located in the vascular hilum at this site. Evidence has accumulated that this connection is critical for local regulation of renin secretion and glomerular vascular tone via the tubuloglomerular feedback mechanism. The tubuloglomerular feedback mechanism maintains a constant chloride concentration at the macula densa at a set point determined by the volume state of the animal, a effect probably important for adjustment of renin secretion to changing salt balance. Evidence supporting these two regulatory roles is reviewed here.
Topics: Animals; Electrolytes; Humans; Juxtaglomerular Apparatus
PubMed: 8743485
DOI: 10.1038/ki.1996.255 -
Hypertension (Dallas, Tex. : 1979) May 2015
Review
Topics: Glomerular Filtration Rate; Humans; In Vitro Techniques; Juxtaglomerular Apparatus; Kidney; Renal Insufficiency, Chronic; Renin-Angiotensin System
PubMed: 25646294
DOI: 10.1161/HYPERTENSIONAHA.114.04365 -
American Journal of Hypertension Jan 1990The tubular-vascular connection via the juxtaglomerular apparatus appears to serve two functions, local control of renal vascular resistance and regulation of renin... (Review)
Review
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.
Topics: Feedback; Glomerular Filtration Rate; Glomerular Mesangium; Humans; Juxtaglomerular Apparatus; Kidney Cortex; Kidney Tubules; Renin; Sodium Chloride
PubMed: 2405885
DOI: 10.1093/ajh/3.1.76 -
Clinical and Experimental Pharmacology... Jul 19971. The juxtaglomerular apparatus (JGA) consists of a tubular component, the macula densa (MD), attached to a vascular component consisting of the afferent and efferent... (Review)
Review
1. The juxtaglomerular apparatus (JGA) consists of a tubular component, the macula densa (MD), attached to a vascular component consisting of the afferent and efferent arterioles and the extraglomerular mesangium. The JGA is richly innervated by sympathetic fibres. 2. The MD is morphologically, histochemically and functionally different from the ascending thick portion of the loop of Henle where it is located. 3. The vascular component includes the vascular smooth muscle cells of the arteriole, the renin-producing cells or juxtaglomerular cells, extraglomerular mesangial cells (Goormaghtigh cells) and endothelial cells. They are coupled by gap junctions. 4. Physiological evidence indicates that the composition of tubular fluid at the MD regulates renin secretion and glomerular haemodynamics and that the JGA is important in the maintenance of body salt-water homeostasis. Evidence suggests that the MD exerts its action on the vascular component through a paracrine mechanism.
Topics: Animals; Gene Expression; Glomerular Mesangium; Immunohistochemistry; In Situ Hybridization; Juxtaglomerular Apparatus; Mice; Nitric Oxide Synthase; Proteins; Rats; Renin
PubMed: 9248671
DOI: 10.1111/j.1440-1681.1997.tb01239.x