Appearance of dense granules in the rough endoplasmic reticulum of the juxtaglomerular cells in mice administered with captopril

The development and fate of the secretory granules in murine, rat and human juxtaglomerular epithelioid cells were examined using ultrastructural and immunocytochemical methods. The formation of mature renin granules occurs by fusion of rhomboid protogranules followed by coalescence of their paracrystalline contents, and by the fusion of roundish juvenile granules having an amorphous internum. Protogranules with paracrystalline contents are prominent in animals with stimulated renin synthesis, indicating an overcharge in processing and/or packaging of the secretory product, renin, under these conditions. Various similarities between lysosomes/multivesicular bodies (MVBs) and juvenile renin granules have been observed. With the exception of small MVBs, no renin-negative organelles that could be regarded as lysosomes were found in epithelioid cells of mice and rats. Therefore, we suggest that renin granules are modified lysosomes. Immunocytochemical findings indicate that juvenile secretory granules of epithelioid cells represent the converting and activating compartment for prorenin. Endocytosed foreign tracers such as HRP or cationized ferritin are preferentially internalized by juvenile renin granules, which hence appear to be outstanding by their fusogeneity. Consequently, juvenile granules are probably responsible for the secretion of prorenin, and mature granules for that of active renin.

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Development and fate of the secretory granules of juxtaglomerular epithelioid cells

Taugner

Metz

1986

Cell Tissue Res.

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The juxtaglomerular apparatus in Bartter's syndrome and related tubulopathies

Taugner

Waldherr

Seyberth

et al. 1988

Vichows Archiv A Pathol Anat

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A comparative immunocytochemical and electron microscopic study was performed on renal biopsies from two children with classical Bartter's syndrome (BS) and three children with a recently described variant, the so-called hyperprostaglandin E-syndrome (HES). Compared to age-matched controls, kidney specimens from patients with BS and HES disclosed a marked hypertrophy and hyperplasia of the juxtaglomerular apparatus (JGA). In addition, in HES focal tubular and interstitial calcifications accompanied by interstitial fibrosis and tubular atrophy were noted. On immunocytochemistry, chronic stimulation of the JGA in BS and HES was characterized by an increase in the number of renin-positive cells, particularly in the media of afferent arterioles, but also in efferent arterioles and in the glomerular stalk. The length of the renin-positive portion of the preglomerular arterioles was significantly increased when compared to controls (100 +/- 32 vs. 49 +/- 17 microns; p less than 0.001). In addition, the immunoreactivity of individual renin-positive cells was markedly enhanced. On electron microscopy, "hypertrophy" of the RER and of Golgi complexes with paracrystalline deposits in dilated RER cisterns and protogranules indicated an increased renin synthesis. Renin could be identified in mature secretory granules as well as protogranules by immune electron microscopy. Angiotensinogen was present in hypertrophied epithelial cells of Bowman's capsule. Converting-enzyme reactivity was observed in controls as well as in BS and HES in the brush border of the proximal tubule. In contrast to previous reports, Angiotensin II was completely negative in control as well as in diseased kidneys. We conclude from our results that both BS and HES are characterized by a marked activation of the JGA and severe stimulation of the renin-angiotensin system. Since activation of this system, however, leads--independently of the primary stimulus--to qualitatively very similar morphological reactions, these results do not implicate a common pathogenetic mechanism to both conditions.

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Differential requirements for CTL generation by novel immunostimulants: APC tropism, use of the TAP-independent processing pathway, and dependency on CD80/CD86 costimulation

Sheikh

Attard

Rooijen

et al. 2003

Vaccine

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Appearance of dense granules in the rough endoplasmic reticulum of the juxtaglomerular cells in mice administered with captopril

Cited by 6 publications

References 11 publications

Development and fate of the secretory granules of juxtaglomerular epithelioid cells

Development and fate of the secretory granules of juxtaglomerular epithelioid cells

The juxtaglomerular apparatus in Bartter's syndrome and related tubulopathies

Differential requirements for CTL generation by novel immunostimulants: APC tropism, use of the TAP-independent processing pathway, and dependency on CD80/CD86 costimulation

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