Urinary kallikrein in dogs with constriction of one renal artery

Effect of upright tilting on kinins as compared to renin activity in the renal venous blood from patients with essential hypertension

The effect of tilting on the release of renal kallikrein as compared to renin was studied by the determination of kinin concentration and plasma renin activity (PRA) in the renal veins in supine position and after 15 min of 45 degrees upright tilting in 10 patients with essential hypertension. Kinin concentration decreased from 0.62 +/- 0.05 microgram/1 (mean +/- S.E.M.) in supine position to 0.51 +/- 0.05 after tilting (p less than 0.01), while PRA increased from 2.84 +/- 0.39 microgram/1/3 h tpo 4.87 +/- 0.66 (p less than 0.001). These results indicate that tilting diminishes the release of renal kallikrein. It is suggested that decreased intrarenal generation of kinins may be of importance for the reduction of diuresis and natriuresis induced by tilting.

Renal venous output of kinins in patients with hypertension and unilateral renal artery stenosis

In four patients with hypertension and angiographically pronounced unilateral renal artery stenosis, kallikrein activity was estimated in each kidney separately by the determination of kinin output in the renal veins. All patients showed suppression of renin release from the kidney with a non-stenotic artery. Accordingly, plasma flow from the kidney with artery stenosis could be estimated. The ratio of venous output of kinins between the kidney with a non-stenotic artery and the one with artery stenosis was 2.6-6.5. This indicates that renal artery stenosis leads to diminished intrarenal kinin generation. Reduced kinin formation may explain the low diuresis and natriuresis found in the kidney with artery stenosis.

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.

Tissue kallikrein in transplant kidney

Literature survey, thus far, has shown a decrease in the excretion of urinary tissue kallikrein (TK) in transplant patients with a further reduction of the enzyme during episodes of acute rejection. The study aims were to compare, at cellular and subcellular levels, the localisation of tissue kallikrein in biopsies of the transplant kidney to autopsy derived normal renal tissue. Renal biopsies from eighteen transplant patients with deteriorating renal function were obtained. Immunolabelling for tissue kallikrein, using a polyclonal goat anti-TK, antibody raised against recombinant TK, was performed following routine enzymatic, immunofluorescence and electron microscopic techniques. In normal kidney tissue, TK was immunolocalised in the distal connecting tubules and collecting ducts. By comparison the renal transplant tissue showed a reduction in the intensity of label, but maintained the sites of localisation. In the sections examined by electron microscopy, although TK was confined mainly at the luminal side of the cell, some label was noted along the basolateral membranes. In the transplant kidneys, there was a reduction in the overall number of gold particles counted, which correlated with the decreased intensity observed on immunocytochemistry. In addition, there was a shift to a basolateral orientation of the immunolabel. Acute rejection is characterised by oedema, tubulitis and vasculitis. Destruction of the tubule cells and leakage of TK into the interstitial tissue space and the resultant effect of the formed kinins on renal capillary vasculature could explain the observed renal parenchymal oedema and transplant rejection.

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.

Sympathetic nervous system mediates urinary kallikrein excretion in conscious rats

1. The influence of the sympathetic nervous system on urinary kallikrein excretion (UKal) was investigated in conscious rats during stress produced by inserting a silastic catheter through the urethra into the bladder. The effect of this stress on blood glucose (BG), mean arterial pressure (MAP), urinary volume (Uv), urinary sodium (UVNa), and glomerular filtration rate (GFR) was also studied. 2. In intact animals stress of 120 min duration produced a non-significant increase of MAP, a significant increase of BG and a decrease of UNa (P less than 0.001 t-test, 9 d.f.), but it did not affect Uv and GFR. In stressed rats UKal was considerably lower (52 milli Amidasic Units [mAU] per 100 g bodyweight, s.e.m. = 5, n = 6) than in control rats (170 mAU per 100 g, s.e.m. = 21, n = 5). The inhibitory effect on UKal was also observed when kallikrein was measured by the kininogenase method. 3. Adrenal medullectomy, performed 1 week before the experiment, suppressed the stress hyperglycaemia but did not affect the reduction of urinary kallikrein or the anti-natriuresis. 4. Intracerebroventricular (i.c.v.) injection of saline also had no effect in the control or in the stressed rats, while i.c.v. d-l-propranolol decreased MAP, suppressed the stress hyperglycaemia and the anti-natriuresis and stimulated UKal, without changes in Uv and GFR. Non-stressed control rats i.c.v. injected with saline excreted considerably less kallikrein than rats i.c.v. injected with d-l-propranolol (control saline: 162, s.e.m. = 14, n = 6; vs control d-l-propranolol: 559, s.e.m. = 20, n = 6). Even in stressed rats this difference was registered (stressed saline: 56, s.e.m. = 8, n = 6; vs stressed d-l-propranolol: 554 mAU per 100 g, s.e.m. = 33, n = 6). 5. Peripheral sympathectomy with 6-hydroxydopamine (6-OHDA) did not suppress the hyperglycaemic response to stress, but it stimulated UKal. Kallikrein excretion was similar in 6-OHDA stressed (534 mAU per 100 g, s.e.m. = 30, n = 6) than in 6-OHDA control rats (491 mAU per 100 g, s.e.m. = 34, n = 6). No differences were observed on UNa and GFR between control 6-OHDA treated rats and stressed 6-OHDA treated rats. 6. The present results suggest strongly that urinary kallikrein excretion is modulated by sympathetic activity. Results after central beta-adrenergic blockade and peripheral sympathectomy led to the hypothesis that normal sympathetic tone in the kidney inhibits the release of kallikrein into the urine.

Vasodepressor role of endogenous bradykinin assessed by a bradykinin antagonist

This study was designed to examine the contribution of bradykinin to the depressor effect of different antihypertensive drugs in two-kidney renovascular hypertensive rats, using a new specific antagonist of bradykinin. First, the inhibitory capacity of this peptide for exogenously injected bradykinin (75-200 ng) was tested. An inhibition of the vasodepressor action of bradykinin by over 50% was found when the bradykinin inhibitor was infused at a rate of 40 micrograms/min, with little difference at higher rates of infusion. This inhibitor then was infused in three groups of renovascular hypertensive rats after their blood pressure had been decreased by pretreatment with the converting enzyme inhibitor enalapril (MK 421), saralasin, or sodium nitroprusside, respectively. Infusion of the inhibitor produced an immediate 30% increase in blood pressure only in the enalapril-treated group. These results indicate that bradykinin is involved in the decrease of blood pressure produced by converting enzyme inhibition in experimental renovascular hypertension.

Hypertensive effect of a bradykinin antagonist in normotensive rats

The purpose of these experiments was to study the possible contribution of bradykinin to normal blood pressure maintenance. The bradykinin analogue B4146, a competitive antagonist-partial agonist of bradykinin, was used in three groups of normotensive unanesthetized Wistar rats. Two intra-aortic injections of B4146 (1 mg in 0.2 ml of dextrose) were given 5 minutes apart (i.e., well after return of blood pressure to baseline, which occurred within 68 +/- 19 seconds). One group had been pretreated with the angiotensin converting enzyme inhibitor HOE 498, 1 mg/kg (Hoechst), and one received only dextrose as the first injection to serve as controls. The bradykinin antagonist produced an average increase in mean arterial pressure of approximately 13 mm Hg for all groups. In five animals, however, the first injection of B4146 produced a hypotensive effect, whereas the second one consistently produced a rise in blood pressure. Pretreatment with the angiotensin converting enzyme inhibitor did not affect the magnitude of the subsequent blood pressure increase in response to B4146. Since smaller doses of B4146, sufficient to block exogenous bradykinin, do not cause changes in normal blood pressure, we conclude that endogenous bradykinin does contribute to normal blood pressure maintenance, but its effect can be demonstrated only if very high doses of its antagonist are injected, maybe because a high concentration of the compound is necessary to displace not only circulating but possibly tissue receptor-bound bradykinin as well.

Effect of prostacyclin on renal kallikrein release in man

The aim of this research was to study exogenous prostacyclin effect on urinary kallikrein excretion (UKK) in man, to define whether prostacyclin-induced renin release and/or endogenously released cyclooxygenase products were responsible for prostacyclin-induced enhancement of UKK, to determine furosemide effect on UKK. Prostacyclin was infused in eight healthy men and repeated after propranolol and indomethacin treatment. Prostacyclin caused a dose-dependent increase of UKK. Pretreatment with propranolol and indomethacin did not affect prostacyclin-induced enhancement of UKK, although it reduced absolute values of plasma renin activity. Furosemide increased UKK and simultaneously urinary 6-keto-prostaglandin F1 alpha. We conclude that prostacyclin induces an increase in UKK in a dose-dependent manner; furosemide-induced renal prostacyclin synthesis is temporally related to enhancement of UKK; partial dissociation of UKK from plasma renin activity under propranolol and indomethacin treatment and in response to furosemide might suggest a direct effect of prostacyclin on UKK.

The two mechanisms involved in the control of urinary kallikrein excretion

The relation between sodium and kallikrein excretion is biphasic. Increased kallikrein excretion is produced by increased arterial pressure or arterial infusion of vasodilators. It is antagonised by prostaglandin synthesis inhibition or by arterial noradrenaline infusion. Angiotensin in hypertensive doses increases kallikrein excretion and this effect is pressure dependent. Decreasing sodium intake, or producing natriuresis with diuretics, causes a rise in kallikrein excretion by stimulation of the renin/angiotensin/prostaglandin/kallikrein chain. It can be mimicked by infusing 50 micrograms/min of angiotensin II into one renal artery with a clamp to prevent elevation of renal arterial pressure.

Kallikrein along the rabbit microdissected nephron: a micromethod for its measurement. Effect of adrenalectomy and DOCA treatment

Active and inactive kallikrein were measured along the rabbit microdissected nephron. A sensitive and specific micromethod for the measurement of kininogenase activity was developed in order to quantify kallikrein in pieces of tubule as small as 0.3-0.5 mm. Our study confirms that active and inactive kallikrein are located to the connecting tubule (CNT). The effects on renal kallikrein of a chronic DOCA treatment and of adrenalectomy were studied. Urinary excretion of kallikrein was also monitored. After DOCA treatment, active kallikrein increased in the tubule and in urine but inactive kallikrein did not significantly change. Adrenalectomy decreased by 50% active and inactive contents of CNT, as well as reduced the excretion of total kallikrein. Kallikrein content in CNT was also measured in adrenalectomized rabbits 3 h after a single injection of either aldosterone (10 micrograms) or dexamethasone (100 micrograms). After either aldosterone or dexamethasone injections, kallikrein activities were not restored, whereas in the same animals Na-K-ATPase activity which was depressed on cortical and medullary collecting tubules after adrenalectomy returned toward normal values. These data indicate that kallikrein synthesis and activation are influenced by adrenal hormones. Renal kallikrein is, however, regulated at a much slower rate than Na+-K+-ATPase. This may suggest an indirect rather than direct action of corticosteroid hormones on kallikrein.

Regulation of kallikrein and renin release by the isolated perfused rat kidney

Rat kidneys perfused in vitro released kallikrein in urine, and renin and kallikrein in the perfusate. The kallikrein was characterized by its kininogenase activity and released bradykinin from bovine and dog substrates. Inactive trypsin activatable kallikrein was present in both perfusate and urine. Kallikrein secretion in urine was influenced by changes in perfusion pressure (PP). Raising the PP strikingly increased urinary kallikrein and lowering PP reduced it. Urinary water and electrolyte output were augmented to the same extent by furosemide and mannitol administration as by raising the PP, but neither drug affected kallikrein. Isoproterenol stimulated the release of renin but not kallikrein. Stopping the oxygen supply to the perfusate suppressed kallikrein secretion in urine and renin release in the perfusate. The kidneys released ten times less kallikrein in the perfusate than in urine, and perfusate kallikrein was not influenced by changes in PP. It is concluded that in this model, changes in PP and/or renal blood flow and/or oxygen supply regulate kallikrein secretion in urine, but that this secretion is unaffected by changes in urinary output. We also conclude that kallikrein release in urine and renin release in perfusate are regulated simultaneously by renal hemodynamic changes but are not affected concomitant by beta-adrenergic stimulation or changes in distal urine composition.

Increased urinary kallikrein excretion in young borderline hypertensive patients

Urinary kallikrein excretion was measured in 46 young patients with borderline hypertension and 28 age-matched normotensive subjects. Hypertensives excreted greater amounts of kallikrein than normotensives (2.31 +/- 0.20 units/day vs. 1.56 +/- 0.17 units/day, p less than 0.01). Plasma renin activity (PRA) was also increased in hypertensives. Moreover, urinary kallikrein was increased in hypertensive patients with high PRA (PRA greater than or equal to mean + 1SEM in normotensives; n = 25) as compared to patients with normal PRA (PRA less than mean + 1SEM; n = 21). In hypertensives with normal PRA, urinary aldosterone correlated to urinary kallikrein (r = 0.478, p less than 0.05), as in normotensives (r = 0.451, p less than 0.02). But, no correlation was found in patients with high PRA. Therefore, the results of the present study do not confirm the hypothesis that the deficiency of the kallikrein-kinin system is the primary cause of hypertension. In hypertensives with high PRA, there may be abnormality of the interaction between the renin-angiotensin-aldosterone system and the kallikrein-kinin system, whereas it may be normal in hypertensives with normal PRA as well as normotensives.

Developmental aspects of the renal kallikrein-like activity in fetal and newborn lambs

The ontogeny of the renal kallikrein-like activity and the interrelationships between this enzyme and the renin-angiotensin-aldosterone and prostaglandin systems were studied in 43 chronically catheterized sheep fetuses between 104 and 142 days of gestation (term, 145 days) and in 8 chronically catheterized newborn lambs between 5 and 23 days of age. Urinary kallikrein (UKall) excretion rate expressed in absolute values (mEU/hr) or corrected for kidney weight (mEU X hr-1 X gKW-1) or glomerular filtration (mEU X hr-1 X ml GFR-1) increased significantly during fetal maturation and after birth. The rise in UKall during fetal and newborn life was not dependent on an increase in urinary flow rate (r = 0.06). The increase in fetal UKall (mEU X hr-1 X gKW-1) correlated closely with the rise in plasma aldosterone concentration for values above 35 pg/ml (r = 0.72, P less than 0.001). A significant negative correlation was found between UKall (mEU X hr-1 X gKW-1) and log of individual urinary sodium excretion values (r = -0.78, P less than 0.001). No correlation was found between UKall and urinary prostaglandins (PGE, PGF2 alpha) excretion during fetal and newborn life, but UKall correlated closely with the rise in renal blood flow during maturation (r = 0.87, P less than 0.001). The present data suggest that aldosterone is an important regulator of UKall release early during development. It is also suggested that conceptional age is an important factor which may modulate the renal sensitivity to aldosterone-stimulated UKall excretion.

Response of the renal kallikrein-kinin system, intravascular volume, and renal hemodynamics to sodium restriction and diuretic treatment in essential hypertension

The renal kallikrein-kinin system, distinct from the plasma system, is an enzyme sequence producing kinins, principally lysyl bradykinin. While the functions of the system have not been conclusively established, it has been implicated in renal vasodilation and natriuresis, although the evidence is often conflicting. Measurement of urinary kallikrein excretion is the most common way to assess the system, although kallikrein excretion and kinin excretion are often dissociated. Kallikrein excretion is influenced by several hormonal systems, as well as dietary alterations, disease states (including hypertension), and numerous drugs. Kallikrein excretion is diminished in hypertension (especially hypertension with reduced renal function), suggesting involvement in the pathogenesis of the disease. Dietary sodium restriction increases kallikrein excretion while lowering blood pressure, but the blood pressure reduction correlates with plasma volume contraction rather than the increase in kallikrein. Thiazide diuretics lower blood pressure and renal vascular resistance while increasing kallikrein excretion, and blood pressure "responders" to thiazides have a greater kallikrein increment than the "nonresponders," suggesting a role for renal kallikrein in the hypotensive response to thiazides.

Antihypertensive effect of orally administered glandular kallikrein in essential hypertension. Results of double blind study

The antihypertensive effect of oral administration of pig pancreatic kallikrein was investigated in a double blind study of 20 patients with essential hypertension. Kallikrein treatment lowered the blood pressure (BP) significantly from 159.5/104.5 to 146.3/92.8 mm Hg in the supine and from 153/106.1 to 136.1/95.6 mm Hg in the standing position. Blood pressure remained unchanged in the placebo group. Urinary kallikrein, sodium excretion, and GFR increased with treatment, but these changes did not reach statistical significance, In the kallikrein-treated patients but not in the placebo group, urinary kallikrein was correlated both to GFR (r = 0.7, p less than 0.001) and sodium excretion (r = 0.5, p less than 0.01). The antihypertensive mechanism of kallikrein treatment remains unknown. It could be speculated that kallikrein may induce changes in local blood flow, mediated by kinin and prostaglandin release.

The effect of hemorrhagic hypotension on urinary kallikrein excretion, renin activity, and renal cortical blood flow in the pig

We measured urinary kallikrein by its esterolytic and kinin-forming activity in 5-minute urine samples obtained throughout continuous bleeding experiments in pigs to correlate possible changes in urinary kallikrein excretion during hemorrhagic hypotension with resin activity and renal cortical blood flow. Renin activity was determined in venous blood samples and renal cortical blood flow was estimated by the radiolabeled microsphere technique. The rate of urinary kallikrein excretion was increased about 4-fold within an arterial pressure range of 100-70 mm Hg, whereas below 70 mm Hg, arterial pressure urinary kallikrein activity declined to undetectable values. Renin activity was increased only 2-fold in the arterial pressure range between 100 and 70 mm Hg but was increased 4-fold at pressures below 70 mm Hg. The pressure range of 100 to 70 mm Hg corresponded to the autoregulation of renal cortical blood flow and glomerular filtration rate; below that pressure range, renal cortical blood flow dropped to about 10% of the initial value. Therefore, it seems that urinary kallikrein is activated mainly during the period of autoregulation, whereas renin activity is, in the main, increased below the autoregulatory range of pressure. The vasodilatory urinary kallikrein kinin system might be involved in maintaining sufficient local blood flow during autoregulation whereas a decrease in blood pressure below the autoregulatory range leads to a major increase in renin activity, thus illustrating the attempt of the organism to reestablish sufficient blood pressure to maintain autoregulation.

Abnormal urinary kallikrein in hypertension is not related to aldosterone or plasma renin activity

The relationships between urinary kallikrein (Ukal), and plasma renin activity (PRA), urinary aldosterone (Ualdo), Na+ balance, SK+, and renal function were studied in essential hypertensives (EHT) and normals. Ukal was measured by a radiochemical esterolytic assay. We studied 18 white patients with EHT (15 men, 3 women) ages 31.6 to +/- 2.1 (SEM) yrs, BP 138 +/- 2/95 +/- 2 mm Hg. and 12 white normals (NLS) (7 men, 5 women) ages 30.2 +/- 2.3 yrs, BP 112 +/- 4/71 +/- 2 mm Hg. All received a 5-day diet of 400 mEq Na+, 80 mEq K+/day, and 5 days of 10 mEq Na+, 80 mEq K+/day. All achieved Na+ balance by Day 5. On Day 5 of the low Na+ diet, 24 hr. Ukal in EHT was 15.8 +/- 2.4 (esterase units/24 hr) vs NLS, 17.0 +/- 2.8 PRA was the same in EHT and NLS, but Ualdo was higher in NLS. (Day 5, low Na+, EHT, Ualdo = 29.4 +/0 3.3 microgram/24h. vs NLS 41.8 +/- 4.7, p less than 0.02). Analysis of individuals showed that all NLS increased Ukal after salt restriction, while 3 EHT decreased Ukal after salt restriction. This abnormal response in EHT was not related to abnormalities in Ualdo, PRA, Na+ balance, SK+, or creatinine clearance. In 3 EHT with low-renin EHT, the Ukal response was normal. In two of four patients with primary aldosteronism, Ukal was normal despite increased Ualdo. The Ukal response to salt restriction is abnormal in some EHT, unrelated to Ualdo or PRA, suggesting either a primary defect in Ukal and/or the presence of other factors modulating Ukal in EHT.

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.

The kallikrein-kinin system in essential hypertension

The kallikrein-kinin system is a potent vasodilator system with components in plasma and in exocrine glands, including the kidney. Kinins function as local hormones and exert effects on blood vessels and on water and electrolyte balance. The most frequently studied component of this system, urinary kallikrein, has been shown to respond to changes in sodium-retaining steroid activity and in renal blood flow. Urinary kallikrein is subnormal in patients with either essential or renovascular hypertension and supranormal in patients with primary aldosteronism or Bartter's Syndrome. The changes in the kallikrein-kinin system appear to be secondary to changes in blood pressure or in other vasoactive systems: i.e., kinins appear to attenuate the vasoconstrictor effects of angiotensin and stimulate the vasodilator actions of the prostaglandins. The kallikrein-kinin system is altered in hypertension, however, its role in this disease remains unclear.

Kallikrein excretion in parotid saliva in rats with various forms of arterial hypertension

A technique for continuous and quantitative collection of parotid saliva--including salivary flow rate determination--for in vivo experiments in rats is described. Excretion of kallikrein-like activity in parotid saliva of rats with various forms of arterial hypertension (genuine, renovascular and DOCTMA-salt hypertension) was studied. Kallikrein excretion was measured by its esterolytic activity. The levels of kallikrein-like activity in parotid saliva of normotensive control rats ranged between 2.5--4.0 mU/min during salivary flow stimulation with pilocarpine. In all forms of experimental hypertension salivary excretion of kallikrein-like activity was increased 2--4 fold. This increase was not related to the activity of the renin-angiotensin system.

Salivary kallikrein excretion in hypertension

According to immunohistochemical investigations kallikrein in the majors salivary glands is located predominantly at the apical border of the striated duct cells and as a luminal rim in the main excretory ducts. Comparatively the highest concentrations are observed in the submandibular gland of rats and cats in the cytoplasmic granules of the granular tubules. In normal humans and rats the kallikrein activity of parotid saliva is inversely related to flow rate and sodium concentration. An increased salivary kallikrein concentration is found in human essential hypertension and renoparenchymal hypertension associated with impaired kidney function. Furthermore in rats with various forms of hypertension (genetic hypertension, DOCTMA salt and renovascular hypertension) the salivary kallikrein secretion - as determined by the BAEE-esterase activity - is enhanced. In contrast to the kallikrein secretion the flow dependent sodium concentration of parotid saliva is reduced in human essential and renoparenchymal hypertension as well as in rats with various forms of experimental and genetic hypertension, which indicates an enhanced sodium reabsorption in the glandular duct system. Furthermore in most forms of hypertension, there is a tendency of higher potassium levels in the saliva. The pathogenesis of the enhanced glandular kallikrein secretion in hypertension is discussed with regard to a counterregulatory mechanism in hypertension as well as to a sympathicoadrenergic activation. The enhanced sodium reabsorption in the duct system in the various forms of hypertension could be the cause as well as a consequence of the enhanced kallikrein secretion.

Urinary kallikrein excretion in idiopathic nephrotic syndrome

The plasma kallikrein-kinin system, a potent vasodilator, has been implicated in causing the protein loss of the idiopathic nephrotic syndrome. However, the kidney possesses a kallikrein-kinin system separate from the plasma system. Thus, urinary kallikrein may reflect more accurately intrarenal events. Using a radiochemical esterolytic assay we measured the urinary kallikrein excretion in a patient with a minimal lesion nephrotic syndrome during relapse. Protein excretion was initially elevated (8.1 plus or minus 2.0 gm. per 24 hours) as was urinary kallikrein excretion (96.4 plus or minus 46.6 EU per 24 hours). After initiation of steroid therapy protein and kallikrein excretion decreased significantly (p less than 0.05). During the entire study kallikrein excretion was significantly correlated with protein excretion (r equals 0.89, p less than 0.01). It is tempting to speculate that activation of the intrarenal kallikrein-kinin system participates in the protein loss characteristic of the nephrotic syndrome.

The effects of ureteral occlusion and renal venous constriction on kidney kallikrein-kinin and prostaglandin systems in dogs

The intrarenal pressure was raised to 40--50 mmHg by ureteral occlusion or by renal venous constriction in anesthetized dogs loaded with 10% mannitol in saline and with a urine flow of approximately 1 ml/min/kidney. Both manoeuvres produced vasodilation and decreased urine creatinine excretion (GFR). Ureteral occlusion was associated with a marked antinatriuresis, which contrasted the variable decrements in sodium excretion during renal venous constriction. Ureteral occlusion did not affect urine excretion of kallikrein or kinins, whilst renal venous constriction decreased urinary kallikrein excretion, yet markedly increased urinary kinin excretion. Ureteral occlusion and renal venous constriction comparably increased urine prostaglandin (E-like) excretion by a presumably pressure dependent mechanism. Inhibition of prostaglandin synthesis by indomethacin abolished the vasodilation during renal venous constriction and this was accompanied by marked reductions of urinary creatinine (GFR) and kallikrein excretions, whilst the kinin excretion was enhanced as observed before the administration of indomethacin.

Increased urinary kallikrein excretion during prostaglandin E1 infusion in anaesthetized dogs and its relation to natriuresis and diuresis

. The effect of intra-arterial prostaglandin E1 (PGE1) infusion on urinary kallikrein, sodium, potassium and water excretion was studied in normal anaesthetized dogs. 2. Infusion of PGE1 caused a dose-related increase in urinary excretion of kallikrein, sodium, potassium and water as well as an increase in renal blood flow (R.B.F.) and a fall in urinary osmolality and renal vascular resistance. 3. The changes occurred in the absence of appreciable changes in inulin clearance (Cin), arterial blood pressure, haematocrit, and plasma sodium and potassium concentrations. 4. The increased urinary kallikrein excretion correlated positively with the natriuresis, diuresis and kaliuresis and the increase in renal blood flow, but negatively with the urinary osmolality and renal vascular resistance. 5. It is concluded that renal kallikrein is involved in the renal response to arterial infusion of PGE1.

A direct assay for urinary kallikrein

The first protein-binding assay is described for the direct determination of kallikrein in rat urine. Isolation of urinary kallikrein and preparation of its specific antibody have been previously described. Outlined here are the methods for 3H-labelling of kallikrein, for isolation of 3H-labelled immunoreactive enzyme, and for separation of free and antibody-bound kallikrein with the aid of double antibody. Assay and equilibrium conditions were characterized and a protocol is presented for the measurement of kallikrein concentration. The direct assay is sensitive, accurate and it correlates well (r = 0.81) with a functional assay. The assay may hold promise to determine catalytically active and inactive enzyme in urine, tissues and biological fluids.

The effect of angiotensin I converting enzyme inhibitor (SQ 20881) on the release of prostaglandins by rabbit kidney, in vivo

1. Prostaglandin E- and F-like material has been estimated in renal venous blood of the left kidney of anaesthetized rabbits following renal nerve section. Prostaglandins were estimated by bioassay following solvent extraction and column chromatography. 2. Electrical stimulation of the renal nerves of the left kidney to reduce renal blood flow by approximately 15% for 15 min resulted in a significant increase in the concentration of prostaglandin E-like material in the renal venous blood. The peak values were normally seen either in the last 5 min of the stimulation period or in the first 5 min after the end of the stimulation period. The concentration of prostaglandin F-like material was not significantly altered. 3. Similar reduction of renal blood flow of the left kidney by renal artery constriction also resulted in a significant increase in the concentration of prostaglandin E- but not F-like material in renal venous blood. The timing and magnitude of the response was comparable with that observed with renal nerve stimuation. 4. The effect of an angiotensin I converting enzyme inhibitor, SQ 20881, on the response to both renal nerve stimulation and renal artery constriction has been studied. The administration of the drug did not significantly reduce the release of prostaglandins from the denervated kidneys, however, the increase in prostaglandin E-like material, in response to both stimuli, was abolished. 5. The results suggest that the increase in prostaglandin E-like material released from the kidney in response to low frequency stimulation or to modest reductions in renal blood flow is dependent on the release of renin and that the effect is mediated by the formation of angiotensin II and not angiotensin I.