The specificity of angiotensin-antisera. A cautionary note

Subcellular localization of angiotensin II immunoreactivity in the rat cerebellar cortex

We localized angiotensin II (Ang II) immunoreactivity in the rat cerebellar cortex with immunogold staining methods. Perfusion fixation with high amounts of glutaraldehyde and the use of cryoultramicrotomy caused remarkable changes in immunostaining versus formaldehyde/picric acid fixation. With the use of monoclonal and polyclonal anti-Ang II, Ang II immunoreactivity was prominent in cerebellar neurons such as Purkinje, granule, basket, and stellate cells. At the subcellular level, the peptide was clearly localized in nuclei, and in some cell types, such as endothelial and granule cells, it was nearly exclusively present in the transcriptionally active euchromatin. Intracellular Ang II immunoreactivity was also detected in vesicle-like structures in cytoplasm and mitochondria and at cell-cell contacts. Additional experiments with liver and adrenal tissue confirmed the nuclear localization of Ang II immunoreactivity, suggesting a role of Ang II in the regulation of gene transcription.

Coexistence of renin and angiotensin II in epitheloid cell secretory granules of rat kidney

The distribution of renin and angiotensin II (ANG II) in juxtaglomerular epitheloid cells of control and adrenalectomized rats was studied, using specific antisera and the protein A-gold technique in Lowicryl- and glycol methacrylate-embedded tissue. The matrix of virtually all mature secretory granules of epitheloid cells contains not only renin, but also ANG II. On adrenalectomy, the concentration of both renin and On adrenalectomy, the concentration of both renin and ANG II in the granule internum increases markedly, as indicated by the density of the immunolabel. Given the coexistence of renin and ANG II in the granule matrix, it is quite probable that, with each secretory event, a certain amount of ANG II is released together with renin. Further experiments will have to show if this amount of ANG II cosecreted with renin is sufficient to elicit immediate local intrarenal actions. ANG I, as well as angiotensinogen and converting enzyme, were not found in epitheloid cells. It is therefore inferred that ANG II is not generated intracellularly, but within the extracellular space and subsequently taken up by pinocytosis and incorporated into the secretory granules of epitheloid cells.

Immunohistochemistry of the renin-angiotensin-system in the kidney

Changes of the intrarenal localization and concentration of renin in comparison to those of angiotensin II (ANG II) are shown under various conditions of stimulation and inhibition of the renin-angiotensin-system. Evidence is presented that ANG II which is detectable by immunocytochemical methods in epitheloid cells is formed locally within the kidney either intra- or extracellularly. ANG II-like activity was found not only in the epitheloid cells of the JGA, but also further upstream in non specialized, "plain" smooth muscle cells of the renal arterial tree and in the medial muscle cells of resistance vessels in other organs and tissues. This ANG II-like activity of resistance vessels is increased in spontaneously hypertensive rats suggesting a possible role in the long-term regulation of blood pressure.