Abstract
Renin-producing cells have been the object of intense research efforts for the past fifty years within the field of hypertension. Two decades ago, research focused on the concept and characterization of the intrarenal renin-angiotensin system. Early morphological studies led to the concept of the juxtaglomerular apparatus, a minute organ that links tubulovascular structures and function at the single nephron level. The kidney, thus, appears as a highly “topological organ” in which anatomy and function are intimately linked. This point is reflected by a concurrent and constant development of functional and structural approaches. After summarizing our current knowledge about renin cells and their distribution along the renal vascular tree, particularly along glomerular afferent arterioles, we reviewed a variety of imaging techniques that permit a fine characterization of renin synthesis, storage, and release at the single-arteriolar, -cell, or -granule level. Powerful tools such as multiphoton microscopy and transgenesis bear the promises of future developments of the field.
Highlights
After summarizing our current knowledge about renin cells and their distribution along the renal vascular tree, along glomerular afferent arterioles, we reviewed a variety of imaging techniques that permit a fine characterization of renin synthesis, storage, and release at the single-arteriolar, -cell, or -granule level
Too, an estimated renin release affecting 40% of cell granules disappearing in 10 minutes [81] is substantially higher than 1-2% release rates obtained in dissected afferent arterioles in rats [96, 114] or rabbits [93] based respectively on renin ultramicro-radioimmunoassay or radioimmunoassay
They have the potential to provide insights into the processing and exocytosis of single renin granules, and may help to approach the “calcium paradox” and the role played by myofilaments in “intermediate” renin cells [95, 137]
Summary
Several recent studies [88, 89] took advantage of previously developped techniques [90] to obtain primary cell cultures of mouse juxtaglomerular renincell cultures, a radioimmunoassay of renin synthesis and renin secretion from these cultures, and combined it with the optical power of fluorescence confocal microscopy These authors [88, 89] demonstrated colocalization of adenylyl cyclase isoform V and renin within granules and provided important clues on signaling mechanisms and proteins involved in renin release. Further studies seem warranted to settle these issues linked to “classic” fluorescence, mono-, or multiphoton imaging in live tissues
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