Localization of Renin in Juxtaglomerular Cells of Rabbit and Dog Through the Use of the Fluorescent-Antibody Technique

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Abstract
Canine antisera to rabbit and hog renin were coupled to several fluorescein dyes. The antiserum was immunologically adsorbed once each with rabbit-liver and with bone-marrow powder, thereby removing excess dye and eliminating nonspecific staining. Mounted frozen-dried sections of kidneys from sodium- deficient rabbits (in which hyperplasia and hypergranulation of juxtaglomerular [JG] cells were present), from control rabbits, from a sodium-deficient dog, and from sodium-deficient rats were treated with the adsorbed labeled antiserum. Ultraviolet microscopy (direct technique) revealed an intense yel low-green fluorescence sharply limited to the granules of the juxtagloinerular cells in all sections studied from kidneys of rabbit and dog. JG granules in rats did not fluoresce, an observation in accord with the species spe cificity of renin. The indirect ("sandwich") method was also employed (with adsorbed, labeled, rabbit antiserum to canine globulin), and although slight staining of gloinerular epithelium resulted, that in the JG granules was far more intense. In our hands, the faint glornerular staining was not blocked by prior treatment with unlabeled renin. Staining of JG granules in any kidney paralleled the intensity of JG granulation by light microscopy and the amount of extractable renin in the same kidney. JG-granule staining (direct and indirect techniques) was blocked by neutralization of the antirenin with renin. Heterogenous anti sera (to insulin; to human gamma globulin) failed to stain. Other rabbit tissues (heart, lung, liver) similarly treated with labeled antirenin never stained. If this work can be repeated with immunologically pure renin, the evidence presented here, together with previously published studies from this and other laboratories, will establish beyond any reasonable doubt that the source of renin in the kidney is the juxtaglomerular cell, as postulated first by Goormagh tigh nearly a quarter of a century ago.