Immunohistochemical localization of renin in luteinizing hormone-producing cells of rat pituitary.

Abstract

The location of renin (EC 3.4.99.19) in rat pituitary was determined by the peroxidase-antiperoxidase immunohistochemical technique. By using antisera prepared with purified rat renal renin, an immunoreactive substance was localized within ovoid cells scattered throughout the anterior pituitary. These cells were shown to be luteinizing hormone-producing cells by staining with anti-luteinizing hormone antisera in adjacent sections. By using the double staining method, the renin-containing cells were differentiated from cells containing corticotropin, thyrotropin, growth hormone (somatotropin), and prolactin (mammotropin). These results suggest a possible local role for renin in the anterior pituitary.Renin (EC 3.4.99.19) (5), while a large amount ofprotease with nonspecific renin-like activity is found in both the anterior and the posterior lobes (unpublished data). Furthermore, in our immunohistochemical studies of the pituitary of the mouse (7) and rat (8), renin-specific staining was observed only in the anterior lobes.A similar lack of agreement is apparent among previous reports with respect to the intrahypophysial localization of angiotensin (9, 10). The consideration of the physiological function of a renin-angiotensin system in the pituitary has been largely focused on the posterior pituitary, presumably in association with the well-known effect of angiotensin II on vasopressin release (11), though the effect may not be exerted in the pituitary. The effect ofangiotensin II on the release ofadrenocorticotropic hormone (ACTH; corticotropin) from the anterior pituitary is also known (12), but the physiological role ofpituitary renin has remained unclear.With the objectives of resolving the existing controversies concerning the location of renin and obtaining clues for the physiological significance of renin in the pituitary, we have applied an immunohistochemical staining technique for the identification of the renin-containing cells in the pituitary.MATERIALS AND METHODS Antisera. Specific antibodies to rat renin were produced in Dutch Belted rabbits by using pure rat renin as antigen. The pure renin was prepared by a published method (13). The enzyme preparation satisfied multiple criteria ofpurity, which included single bands upon polyacrylamide gel electrophoresis, sodium dodecyl sulfate gel electrophoresis, isoelectric focusing, and double immunodiffusion and symmetric chromatographic elution patterns. This preparation (1.0 mg) was conjugated to 0.5 mg of tetanus toxoid with 25 ,ug of water-soluble carbodiimide and exhaustively dialyzed, and then an aliquot containing 80 ug of renin was mixed with an equal volume of complete Freund's adjuvant and injected intradermally at multiple sites in the back ofeach rabbit. After six biweekly boosters, each with the conjugate equivalent of 10 ,.g of renin, antisera were collected. Tested at dilutions greater than 1:500, these antibodies did not crossreact with human renin or rat cathepsin. Used at 1:2000 dilution for immunohistochemical staining of ra...

Immunocytochemical Localization of Angiotensinogen and Angiotensin II in the Rat Pituitary

“…However, by increasing the sensitivity of our immunocytochemistry we have been able to establish its presence in anterior pituitary glandular cells, including AII-containing gonadotrophs. These results, in addition to the reported presence of renin (17) and converting enzyme (22) in these cells, show that the strong AII-immunoreactivity of gonadotrophs is due to the intracellular generation of this peptide and not from the uptake of extracellular AII. The light immunostaining for angiotensinogen does not glial origin due t o their positive immunoreactivity, in a number of species, for glial cell markers such as glial fibrillary acidic protein, vimentin, and S-100 protein (38)(39)(40).…”

“…Several observations support the idea of a functioning RAS in the pituitary: 1) the demonstration of renin (16)(17)(18)(19) and converting enzyme in the pituitary (20)(21)(22)(23); 2) the detection of renin mRNA in pituitary extracts (24); 3) the identification and HPLC characterization of A11 from the hypophysis (25, 26); 4) the colocalization, by immunocytochemistry, of both renin and A11 in the rat gonadotroph (19,27) or human lactotroph (28); and 5) the demonstration of specific A11 receptors in the pituitary (9-1 1). However, the existence of angiotensinogen, the only known precursor of the angiotensin peptides, in pituitary cells has yet to be definitively established.…”

“…(17,19,27), converting enzyme (22) and A11 (19,26,27) have been found in gonadotrophs, Saint-Andre et al (28) observed angiotensinogen, renin and converting enzyme in lactotrophs. In the present study, angiotensinogen and A11 colocalized within gonadotrophs, but not lactotrophs, in agreement with the above studies in the rat.…”

Autoradiographic localization of angiotensin II receptors in rat brain.

“…All components of the renin-angiotensin system (3), including renin (7,8), angiotensin-converting enzyme (9)(10)(11)(12)(13), and the polypeptide precursor angiotensinogen (14), have been identified in the brain. Renin has been localized in neurones of the medulla oblongata, cerebellar nuclei, and hypothalamus (15) and in cells of the anterior pituitary (16). All-containing nerve terminals and neurones have been localized in brain by immunohistochemistry (17)(18)(19)(20)(21)(22).…”

Localization of Components of the Renin-Angiotensin System within the Kidney and Sustained Release of Angiotensins from Isolated and Perfused Kidney.

“…Under normal conditions, Ang I could not be detected in rat JG cells with immunohistochemical staining by using the unlabeled antibody peroxidase-antiperoxidase (PAP) method (Sternberger 1979;Naruse et al 1981). However, when rats were treated with angiotensin-onverting enzyme (ACE) inhibitors (captopril or MK 421) for 2 weeks, Ang I was clearly observed in JG cells in which Ang I and renin were localized, as shown in Figs.…”