Evidence exists for the presence of a discrete tissue renin-angiotensin system (RAS) in mouse and rat pancreas that is thought largely to be associated with the vasculature. To investigate this in the human pancreas, and to establish whether the cellular sites of RAS components include the islets of Langerhans, we used immunocytochemistry to localise the expression of angiotensin II (AT1) receptors and (pro)renin, and non-isotopic in situ hybridisation to localise transcription of the (pro)renin gene. Identification of cell types in the islets of Langerhans was achieved using antibodies to glucagon and insulin.The results show the presence of the AT1 receptor and (pro)renin both in the beta cells of the islets of Langerhans, and in endothelial cells of the pancreatic vasculature. Transcription of (pro)renin mRNA, however, was confined to connective tissue surrounding the blood vessels and in reticular fibres within the islets. These findings are similar to those obtained in other tissues, and suggest that renin may be released from its sites of synthesis and taken up by possible cellular sites of action.The results presented here suggest that a tissue RAS may be present in human pancreas and that it may directly affect beta cell function as well as pancreatic blood flow.

Summary We demonstrate the expression of angiotensin 11 type 1 (AT1) receptors in normal and diseased human breast tissues. Using monoclonal antibody 6313/G2, directed against a specific sequence in the extracellular domain of the AT1 receptor, immunocytochemical analysis revealed positive immunoreactivity in membrane and cytoplasm of specific cell types. Immunoblotting of solubilized proteins separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) from benign and malignant tumours identified a single immunoreactive species with a molecular mass of approximately 60 kDa, consistent with that of the mature glycosylated receptor. In studies of [1251]angiotensin 11 binding using breast membrane preparations, concentrations of specific angiotensin 11 binding sites were found to range from 1.8 to 100 fmol mg-' protein, with a Kd of approximately 60 nm. Most of the specifically bound [1251]angiotensin II was displaced by losartan, a specific angiotensin 11 type 1 receptor antagonist, while less was displaced by the AT2 receptor type antagonist, CGP42112A, thus confirming the prevalence of AT1 receptors in this tissue type. These data suggest that the renin-angiotensin system may be involved in normal and abnormal breast tissue function.Keywords: breast cancer; renin-angiotensin system; losartan; immunocytochemistry; monoclonal antibody G313/G2 Angiotensin II plays a central role in mammalian electrolyte homeostasis and blood pressure control (Peach, 1977;Vinson et al, 1992). Two main subtypes of angiotensin II receptors, designated types 1 and 2 (ATl and AT2), have been recognized, but the majority of the well-known actions of angiotensin II occur via the ATI subtype (Herblin et al, 1991;Ouali et al, 1992). Local tissue renin-angiotensin systems have been demonstrated in several tissues, and in some cases it has been suggested that local production of angiotensin II may be particularly concerned in trophic actions (Vinson et al, 1995a).The availability of our recently developed monoclonal antibody (6313/G2) to the ATI receptor subtype (Barker et al, 1993a) has facilitated the further study of its distribution (Vinson et al, 1995a). We describe here studies investigating the presence of the ATl receptor in normal and diseased breast. Sections were then immersed in endogenous peroxidase blocking solution (3 ml of 100 volume hydrogen peroxide and 97 ml of methanol; 15 min), washed in tap water (10 min) and distilled water (5 min). Sections were immersed in 10 mm citrate buffer, pH 6.0, covered loosely with 'Saranwrap' (Dow Chemical Co.) and boiled in a microwave oven for 10 min at 630 w (H2500 BioRad, Watford, Herts., UK). After standing for 10 min in hot buffer, sections were washed in tap water (5 min) and transferred to 0.05 M Tris-buffered saline, pH 7.6 (TBS). MATERIAL AND METHODSTissue sections were then incubated with normal rabbit serum (Dako, High Wycombe, Bucks., UK) diluted 1:5 in Tris-buffered saline (20 min) and incubated (60 min) with mouse primary antibody 6313/G2 (Barker et al, 1...

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