Kininogen in human urine [proceedings]

A missing link between a high salt intake and blood pressure increase

It is widely accepted that a high sodium intake triggers blood pressure rise. However, only one-third of the normotensive subjects were reported to show salt-sensitivity in their blood pressure. Many factors have been proposed as causes of salt-sensitive hypertension, but none of them provides a satisfactory explanation. We propose, on the basis of accumulated data, that the reduced activity of the kallikrein-kinin system in the kidney may provide this link. Renal kallikrein is secreted by the distal connecting tubular cells and all kallikrein-kinin system components are distributed along the collecting ducts in the distal nephron. Bradykinin generated is immediately destroyed by carboxypeptidase Y-like exopeptidase and neutral endopeptidase, both quite independent from the kininases in plasma, such as angiotensin converting enzyme. The salt-sensitivity of the blood pressure depends largely upon ethnicity and potassium intake. Interestingly, potassium and ATP-sensitive potassium (K(ATP)) channel blockers accelerate renal kallikrein secretion and suppress blood pressure rises in animal hypertension models. Measurement of urinary kallikrein may become necessary in salt-sensitive normotensive and hypertensive subjects. Furthermore, pharmaceutical development of renal kallikrein releasers, such as K(ATP) channel blockers, and renal kininase inhibitors, such as ebelactone B, may lead to the development of novel antihypertensive drugs.

The renal kallikrein-kinin system: its role as a safety valve for excess sodium intake, and its attenuation as a possible etiologic factor in salt-sensitive hypertension

The distal tubules of the kidney express the full set of the components of the kallikrein-kinin system, which works independently from the plasma kallikrein-kinin system. Studies on the role of the renal kallikrein-kinin system, using congenitally kininogen-deficient Brown-Norway Katholiek rats and also bradykinin B2 receptor knockout mice, revealed that this system starts to function and to induce natriuresis and diuresis when sodium accumulates in the body as a result of excess sodium intake or aldosterone release, for example, by angiotensin II. Thus, it can be hypothesized that the system works as a safety valve for sodium accumulation. The large numbers of studies on hypertensive animal models and on essential hypertensive patients, particularly those with salt sensitivity, indicate a tendency toward the reduced excretion of urinary kallikrein, although this reduction is modified by potassium intake and impaired renal function. We hypothesize that the reduced excretion of the renal kallikrein may be attributable to a genetic defect of factor(s) in renal kallikrein secretion process and may cause salt-sensitive hypertension after salt intake.

Pivotal role of renal kallikrein-kinin system in the development of hypertension and approaches to new drugs based on this relationship

Renal kallikrein is one of the tissue kallikreins, and the distal nephron is fully equipped as an element of the kallikrein-kinin system. Although a low excretion of urinary kallikrein has been reported in essential hypertension, the results from studies on patients with hypertension are not consistent. Congenitally hypertensive animals also excrete lowered levels of urinary kallikrein, but the effects of this are yet unknown. Extensive genetic and environmental studies on large Utah pedigrees suggest that the causes of hypertension are closely related to the combination of low kallikrein excretion and the potassium intake. Mutant kininogen-deficient Brown Norway-Katholiek rats, which cannot generate kinin in the urine, are very sensitive to salt loading and to sodium retention by aldosterone released by a non-pressor dose of angiotensin II, which results in hypertension. The major function of renal kallikrein-kinin system is to excrete sodium and water when excess sodium is present in the body. Failure of this function causes accumulation of sodium in the cerebrospinal fluid and erythrocytes, and probably in the vascular smooth muscle, which become sensitive to vasoconstrictors. We hypothesize that impaired function of the renal kallikrein-kinin system may play a pivotal role in the early development of hypertension. Inhibitors of kinin degradation in renal tubules and agents, which accelerate the secretion of urinary kallikrein from the connecting tubules and increase the generation of urinary kinin, may be novel drugs against hypertension.

Effect of bradykinin and tachykinin receptor antagonist on xylene-induced cystitis in rats

The effects of the bradykinin receptor selective antagonist, Hoe 140, and of the tachykinin NK-1 receptor antagonist (+/-)CP 96,345 were investigated in a rat model of chemically-induced cystitis (intravesical instillation of xylene in female rats). Intravenous injection of bradykinin (1 mumol./kg.) or substance P (3 nmol./kg.) produced plasma protein extravasation (PPE) in the rat urinary bladder. Bradykinin response was prevented by Hoe 140 (100 nmol./kg. intravenously) and unaffected by (+/-)CP 96,345 (10 mumol./kg. intravenously). Plasma protein extravasation produced by substance P was inhibited by (+/-)CP 96,345 but unchanged by Hoe 140. Catheterization required for intravesical xylene instillation into the female rat bladder produced per se an inflammatory response which was abolished by either Hoe 140 or (+/-)CP 96,345. Intravesical instillation of xylene produced a large PPE response which was reduced by about 65% by Hoe 140 or (+/-)CP 96,345. Combined administration of the two antagonists produced an additive effect on the PPE response to xylene. We conclude that both bradykinin and tachykinins are involved in the inflammatory reaction of the rat urinary bladder to catheterization and xylene irritation.

Evidence for the involvement of bradykinin in chemically-evoked cystitis in anaesthetized rats

The effect of Hoe 140, a potent bradykinin B2 receptor antagonist, on the micturition reflex and detrusor hyperreflexia induced by chemical cystitis has been investigated in anaesthetized rats. Hoe 140 (1-100 nmol/kg i.v.) produced a dose-dependent blockade of the contraction of the rat urinary bladder induced by i.v. administration of bradykinin (100 nmol/kg) without affecting the response produced by the selective tachykinin NK-1 receptor agonist, [Sar9] substance P (SP) sulfone (1 nmol/kg i.v.). At doses which produce selective and long-lasting blockade of bradykinin receptors in the urinary bladder, Hoe 140 did not modify urodynamic parameters in normal rats. Intravesical instillation of xylene in female rats decreased bladder capacity and increased micturition frequency. These effects also occurred in rats pretreated with capsaicin as adults. Hoe 140 did not modify xylene-induced cystitis. Intraperitoneal administration of cyclophosphamide (150 mg/kg, 48 h before) decreased bladder capacity and increased micturition frequency. These effects of cyclophosphamide were abolished in rats pretreated with capsaicin as adults. Hoe 140 increased bladder capacity and decreased micturition frequency in rats pretreated with cyclophosphamide. Addition of bradykinin (10 mumol/l) to the medium in the superfused rat urinary bladder preparation evoked a prompt increase in the outflow of calcitonin gene-related peptide like immunoreactivity (CGRP-LI). Hoe 140 (3 mumol/l) inhibited (by about 50%) the CGRP-LI out-flow stimulated by bradykinin. These findings demonstrate the participation of bradykinin, through B2 receptors, in the genesis of detrusor hyperreflexia during cyclophosphamide-induced cystitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Local motor responses to bradykinin and bacterial chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP) in the guinea-pig isolated renal pelvis and ureter

The local motor response to bradykinin and the bacterial chemotactic peptide, formyl-methionyl-leucyl-phenylalanine (FMLP) was investigated in the guinea-pig isolated renal pelvis and ureter in relation to possible activation of capsaicin-sensitive primary afferent nerves and release of sensory neuropeptides. Both bradykinin (1 nM-10 microM) and FMLP (10 nM-10 microM) produced a concentration-dependent positive inotropic effect in the isolated renal pelvis which was unaffected by in vitro capsaicin desensitization. The response to bradykinin was antagonized by HOE 140, a bradykinin receptor antagonist, while it was unaffected by MEN 10,376, a tachykinin receptor antagonist, hCGRP(8-37) a calcitonin gene-related peptide (CGRP) receptor antagonist and N-t-BOC-Phe-DLeu-Phe-DLeu-Phe (BPLPLP), an FMLP antagonist. The response to FMLP was blocked by BPLPLP while it was unaffected by HOE 140, MEN 10,376 or hCGRP(8-37). Indomethacin (10 microM) enhanced the response to both bradykinin and FMLP. Bradykinin transiently activated rhythmic contractions in the isolated ureter. The response to bradykinin was blocked by HOE 140 and was unaffected by in vitro capsaicin desensitization, indomethacin, MEN 10,376 or BPLPLP. FMLP had no motor effect on the resting ureter but when rhythmic background contractions were evoked by the addition of 100 nM endothelin 1, it produced a transient suppression of ureteral motility. This inhibitory effect was unchanged by in vitro capsaicin desensitization or HOE 140 while it was abolished by indomethacin or BPLPLP pretreatment. Both bradykinin and FMLP evoked the release of CGRP-like immunoreactivity in the renal pelvis. The effect of bradykinin but not that of FMLP was abolished by indomethacin. By contrast neither bradykinin nor FMLP did evoke a significant CGRP-LI release in the ureter. It is concluded that bradykinin and FMLP affect pyeloureteral motility through specific and independent pathways. The local motor responses produced by these chemical stimulants are independent from the release of sensory neuropeptides from capsaicin-sensitive primary afferent neurons. Direct neurochemical evidence was obtained for activation of capsaicin-sensitive primary afferents in the renal pelvis: such a mechanism could be involved in the genesis of ureteral pain whenever bradykinin or FMLP come into contact with sensory nerves in the pyeloureteral wall.

Localisation of immunoreactive kininogen and tissue kallikrein in the human nephron

The cellular localisation of kininogen and its relationships with tissue kallikrein containing cells was studied in the human kidney by the peroxidase-antiperoxidase method using antisera to human LMW kininogen and to human tissue kallikrein. Immunoreactive kininogen was localised in the principal cells of collecting ducts. Immunoreactive tissue kallikrein was detected in the connecting tubule cells, segment of the nephron preceding the cortical collecting ducts. The co-existence of tissue kallikrein and kininogen in the same transitional tubule, but in different cells, was established by the use of serial sections and double immunostaining. This anatomical relationship is in accordance with known studies that describe intermingling of principal cells and connecting tubule cells where connecting tubules merge into cortical collecting ducts in the human nephron. The close relationship between cells that contain tissue kallikrein and its substrate, kininogen, suggests that kinins could be generated in the lumen of distal cortical segments of the human nephron.

Effects of changing salt and water balance on renal kallikrein, kininogen and kinin

The kallikrein-kininogen-kinin system (KKK) has been implicated in the renal sodium excretion response to changes in dietary sodium. However, both increases and decreases in the activity of this system have been observed when urinary sodium excretion is augmented by a variety of maneuvers. To further evaluate the potential physiologic role of this system, we measured three components of the KKK system in urine. Total kallikrein, intact kininogen, and kinin were measured twice in normal individuals during balance on both a high (250 mEq/day) or low (10 mEq/day) sodium intake. A consistent and significant reduction in the activity of all three components of the KKK system was noted during the high salt intake. Furthermore, during the high sodium intake, further acute reductions in components of this system were observed when an acute saline but not water load was administered. The consistent response of the various components of the KKK system to both acute and chronic sodium loading suggests that the system is physiologically linked to the regulation of sodium balance. However, the directional changes argue against a primary natriuretic effect of this system.

The role of urinary kininogen in the regulation of kinin generation

The kallikrein-kininogen-kinin system has been postulated to play a role in the regulation of blood pressure and modulation of renal salt and water transport. The activity of this system has usually been determined by measurements of urinary kallikrein excretion. However, urinary kallikrein rarely correlates with simultaneously measured urinary kinins. To further evaluate the factors influencing urinary kinin excretion, we evaluated the role of urinary kininogen in this system. Urines were analyzed from normal subjects and individuals with untreated essential hypertension and end-stage renal disease. Intact urinary kininogen was significantly correlated with urinary kinins in normal subjects (r = 0.65, P = 0.003) and essential hypertensives (r = 0.52, P = 0.026). In both essential hypertension and end-stage renal disease, urinary kinins were significantly decreased (8.00 +/- 1.93, 0.90 +/- 0.18, P less than 0.05, respectively) compared to controls (23.73 +/- 5.20). In essential hypertensives, the reduction in urinary kinins was paralleled by a reduction in intact kininogen with a normal excretion of kallikrein. In end-stage renal disease, the reduction in kinins was paralleled by a reduction in kallikrein with a normal excretion of intact kininogen. This data suggests that kininogen may be an important determinant of urinary kinin excretion in various disease states.

Inhibition of the ureteral contractions induced by rat urine with kallikrein antibodies

Purified urinary kallikrein induces contractions of the rat ureter in vitro. Antibodies against kallikrein block the contractile response of the isolated ureter to rat urine.

Kinins in relation to kallikrein activity, kininogen, electrolytes, aldosterone and catecholamines in urine from normal individuals

The object of the present study was to test the hypothesis that urinary kinin excretion is an indicator of intrarenal kinin formation and to investigate urinary excretion of kinins in relation to natriuresis, kaliuresis, diuresis and urinary aldosterone and catecholamines in normal individuals on a free salt and water intake. In freshly voided urine collected from 24 normal individuals kinin concentration was directly related to kallikrein activity. Kininogen concentration was very low and neither related to kallikrein activity nor to kinin concentration. The excretion rates of kinins and kininogen were unrelated to the time interval between micturitions. In 24 hour urine collections from 50 normal individuals the excretion of kinins was positively correlated to natriuresis, kaliuresis and diuresis and also to dopamine but not to aldosterone, noradrenaline and adrenaline. Kinin excretion was inversely related to age and was lower in women than in men. On the basis of these results it is concluded that urinary kinin excretion reflects intrarenal kinin formation in normal ambulatory individuals and that urinary kinins are formed mainly in the interstitial and vascular space of the kidney. Furthermore, kinins and dopamine seem to play a physiological role in the renal handling of electrolytes and water.

Changes of urinary kallikrein and kinin excretions induced by adrenalin infusion in conscious dogs

A subpressor dose of adrenalin (0.5 mg/h) infused intravenously into nine conscious trained dogs increased urine kinin excretion from 41 +/- 9 ng/h to 191 +/- 29 ng/h. The effect was abolished by phenoxybenzamin pretreatment (1 mg/kg). In alpha-blocked condition adrenalin increased urine TAMe-esterase activity from 12.7 +/0 2.3 mEU/h to 15.7 +/- 2.8 mEU/h whilst in beta-blocked condition the catecholamine decreased urine enzyme activity from 12.7 +/- 1.0 mEU/h to 11.7 +/- 1.1 mEU/h. Adrenalin invariably decreased urine sodium excretion. In comparable experiments with dopamin (1.0 mg/h) a slight natriuresis was observed, yet urine kallikrein and urine kinin excretions remained unmodified.

Studies on rat renal cortical cell kallikrein. II. Identification of kallikrein as an ecto-enzyme

Suspensions of viable renal cortical cells hydrolyzed a synthetic ester substrate (alpha-N-tosyl-L-arginine methyl ester, Tos-Arg-OMe) and generated kinins from a kininogen substrate. This kallikrein-like esterase activity increased linearly with cell number, or time of exposure to substrate. No radiolabelled substrate or product was found within the cells. Most of the activity appeared to be on cell surfaces as supernatant media had less than 20% of the Tos-Arg-OMe esterase activity on the cell suspensions. Cell surface Tos-Arg-OMe esterase activity was inhibited by aprotinin, benzamidine, pentamidine, and a tris-amidine derivative (alpha,alpha',alpha''-tris(3-amidinophenoxy)mesitylene). Preincubation of cells with phospholipase A2 increased renal cell surface esterase activity up to 76% while only slightly increasing supernatant activity. In contrast, preincubation with deoxycholate caused clearing of suspensions and a marked increase in supernatant esterase activity. Renal cell kininogenase (EC 3.4.21.8) activity was inhibited by preincubation with aprotinin, the tris-amidine derivative, or anti-rat urinary kallikrein antibody. Kallikrein elaborated by renal cells formed a single precipitin line with an antibody to rat urinary kallikrein but the two enzymes were not immunologically identical. We conclude that kallikrein's active sites are facing the external environment of renal cortical cells in suspension with access to substrates, inhibitors, and antibody.