Gap junctional coupling between the JGA and the glomerular tuft

Abstract

The juxtaglomerular apparatus (JGA) in the rabbit kidney was examined by transmission electron microscopy and by freeze fracturing. It was found, that the Goormaghtigh cells of the JGA are extensively coupled with the mesangial cells within the glomerular tuft by gap junctions. A broad band of gap junctions starting within the Goormaghtigh cells, traversing the transitional area at the root of the glomerular tuft and continuing along the mesangial cells has been revealed by freeze fracturing. No gap junctional connections to the macula densa cells have been found. In accordance with data from literature it may be stated that all smooth muscle derived cell groups at the vascular pole of the glomerulus (smooth muscle cells of the vas afferens and efferens, granular cells, Goormaghtigh cells, mesangial cells) are extensively coupled by gap junctions with each other. It is supposed that this cell system may act as a synchronized functional unit.

Connexin 40 Mediates the Tubuloglomerular Feedback Contribution to Renal Blood Flow Autoregulation

“…32 Alternatively or in addition, ATP may contract afferent arterioles by activating purinergic P2X receptors. 18,31 Given the high prevalence of gap junctions in the JGA, 9 the signal transduction of TGF might also follow a transcellular route from the macula densa through extraglomerular mesangial cells to the afferent arteriole. 9,17,33 Recent studies showed mesangial propagation of TGF-induced calcium waves from the macula densa to glomerular and arteriolar sites.…”

“…18,31 Given the high prevalence of gap junctions in the JGA, 9 the signal transduction of TGF might also follow a transcellular route from the macula densa through extraglomerular mesangial cells to the afferent arteriole. 9,17,33 Recent studies showed mesangial propagation of TGF-induced calcium waves from the macula densa to glomerular and arteriolar sites. 18 Because mesangial cells express several P2 receptors, 31 they may be activated by ATP released from the macula densa.…”

“…8 Within the kidney, gap junctions are prevalent in the juxtaglomerular apparatus (JGA). 9 The JGA is a unique structure coordinating tubular function to the regulation of preglomerular vasomotor tone and renin release. Cx40 is the predominant connexin in the JGA, with expression in endothelial and renin-producing cells of afferent arterioles and glomerular mesangial cells.…”

From tubular sublimate nephropathy via urinary concentrating mechanism to glomerular disease—Wilhelm Kriz’s contribution to modern nephrology

“…Stimulated by the particular interest of nephrologists in the mesangium, its physiological functions, and its assumed central role in glomerular disease at that time, Kriz focused his research interest on the general mesangial tissue structure, mostly of the intraglomerular mesangium, but also, with respect to juxtaglomerular function, of the then still enigmatic BPolkissen^(lacis cells of Goormaghtigh) or extraglomerular mesangium. On the one hand, the relation of mechanical forces transmitted between mesangium and glomerular basement membrane was clarified, and on the other, the Polkissen was meticulously described with respect to its intimate neighborhood [74,89,94,96], although better clarification of its role still had to wait a number of years until Jürgen Schnermann was able to identify a major signaling pathway involving adenosine and adenosine receptors. Since at that time, the structure and function of the renin-containing granular cells of the afferent arteriole were subject to lively discussions [72], Kriz described a periarterial space thought to be relevant for intrarenal renin distribution upon cellular release [38].…”

The Goldblatt memorial lecture. Part I: Experimental renovascular hyptertension.

“…Recently Taugner and co-workers, 49 using freeze fracture techniques, have demonstrated gap junctions between most of the cellular elements of the juxtaglomerular apparatus, hydrophillic channels which allow the passage of ions and small molecules from cell to cell without significant leak into the extracellular space. Their observation that is particularly surprising is the absence of gap junctions between the macula densa cells and the other cells of the region, a finding to which I shall return in a moment.…”