Active and inactive kallikrein in rabbit connecting tubules and urine during low and normal sodium intake

Abstract Active and inactive kallikrein in rabbit connecting tubules and urine during low and normal sodium intake. Active and total (trypsin-activated) kallikrein were measured in urine and the discrete segments of the nephron of rabbits fed low and normal sodium diets. Kallikrein was measured by its kininogenase activity, and kinins generated were measured by radioimmunoassay. The amount of inactive kallikrein was calculated as the difference between total and active kallikrein. The nephrons were microdissected and divided into eight segments: (1) glomerulus; (2) proximal convoluted tubule; (3) cortical thick ascending limb; (4) bright portion of distal convoluted tubule; (5) granular portion of distal convoluted tubule; (6) granular portion of cortical collecting tubule; (7) light portion of cortical collecting tubule; and (8) medullary collecting tubule. As we have previously described, active and inactive kallikrein were localized mainly in the granular portion of the distal convoluted and cortical collecting tubules (connecting tubule). Both active and inactive kallikrein in the granular portion of the distal convoluted and cortical collecting tubule increased markedly during low sodium intake without altering the distribution profile. Urinary excretion of active and inactive kallikrein also increased significantly in the low sodium diet. More than 50% of total kallikrein was found in the inactive form in the nephron and urine. The ratio of active to total kallikrein in the nephron and urine was not changed by sodium restriction. These results suggest that sodium restriction stimulates the biosynthesis and excretion of both active and inactive kallikrein. Kallikreine active et inactive dans les tubes connecteurs et les urines de lapin pendant un apport sodique faible ou normal. Les kallikreines active et totale (activee par la trypsine) ont ete mesurees dans les urines et sur des segments isoles de nephrons de lapins recevant des regimes pauvre ou normal en sodium. La kallikreine a ete mesuree par son activite kininogenase et les kinines generees ont ete mesurees par dosage radioimmunologique. La quantite de kallikreine inactive a ete calculee par difference entre les kallikreines totale et active. Les nephrons ont ete microdisseques et divises en huit segments: (1) le glomerule; (2) le tubule contourne proximal; (3) l'anse ascendante large corticale; (4) la partie brillante du tube contourne distal; (5) la partie granulaire du tube contourne distal; (6) la partie granulaire du canal collecteur cortical; (7) la partie fine du canal collecteur cortical; (8) le canal collecteur medullaire. Comme nous l'avons precedemment decrit, les kallikreines active et inactive etaient essentiellement localisees dans la partie granulaire des tubules contournes distaux et des canaux collecteurs corticaux (segments de connexion). Les kallikreines active et inactive de la portion granulaire du tubule collecteur contourne distal cortical se sont elevees de facon importante pendant un faible apport sode, sans modification du profil de distribution. L'excretion urinaire de kallikreines active et inactive a egalement augmente significativement pendant le regime pauvre en sodium. Plus de 50% de la kallikreine totale etait trouvee sous une form inactive dans le nephron et les urines. Le rapport kallikreine active sur kallikreine totale dans le nephron et les urines n'etait pas modifie par la restriction sodee. Ces resultats suggerent que la restriction sodee stimule la biosynthese et l'excretion des kallikreines active et inactive.