Measurement of Kallikrein Activity in Urine of Rats and Man Using a Chromogenic Tripeptide Substrate. Validation of the Amidolytic Assay by Means of a Bradykinin Radioimmunoassay

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The measurement of amidolytic activity in kidney homogenates for the estimation of renal kallikrein

Renewed interest in the kallikrein-kinin system was awakened in the early seventies by the suggestion that it might be involved in the regulation of sodium excretion [1, 2] or in the development of hypertension [3, 4]. However, due to complexities inherent in the measurement of the enzyme in the kidneys, only a few reports on the activity of the renal kallikrein have been published to date [5–8]

The Involvement of Urinary Kallikrein in the Renal Escape from the Sodium Retaining Effect of Mineralocorticoids

It is well known that the normal kidney escapes the sodium retaining effect of mineralocorticoids. However, the mechanism that mediates this escape is not understood. The possible role of kallikrein in this escape phenomenon was investigated by placing seven dogs in metabolic cages and giving them a constant sodium diet. After they had been on this diet three days, urine was collected for two 24-hour periods. DOCA (25 mg/day) was then given intramuscularly for five days. Urine was collected daily during this DOCA period and for two additional 24- hour periods. Urine volume, sodium, potassium, protein, and kallikrein excretion were then measured. Urinary kallikrein increased from 251.9 ± 34.8 (mean ± SE) in the second day of the control period to 639.8 ± 110.1 IJ-g/day (P \u3c .01) by the third day of treatment. It remained elevated two days after DOCA was discontinued. Sodium excretion decreased significantly on the first day of DOCA treatment, returning to the previous values thereafter. Urine protein excretion remained constant. The enhanced urinary kallikrein during the escape suggests that the kallikrein system could be involved in the regulation of sodium metabolism by acting as a natriuretic factor, or perhaps by regulating the renal blood flow

Lithium treatment reduces the renal kallikrein excretion rate

Lithium treatment reduces the renal kallikrein excretion rate. Lithium salts are widely used agents for the prophylactic treatment of affective disorders. Lithium salts may be associated with distal nephron dysfunction. Kallikrein is a protease which is generated by the distal nephron. We used an amidolytic assay of chromatographically purified enzyme to determine the urinary excretion rate of active kallikrein in relation to lithium treatment. All plasma lithium concentrations were within the therapeutic range (0.4 to 0.9 mmol/liter). In 15 patients the urinary excretion rate of active kallikrein was 267.4 65.6 mU/24 hrs before lithium treatment, and fell to 117.8 39.6 mU/24 hrs (P < 0.05) on day 14 of lithium treatment. This reduction was associated with a decrease of immunoreactive kallikrein in the same urines by 66%. In another 15 patients who had undergone lithium therapy for an average period of 5.6 years, the urinary excretion rate of active kallikrein was 86.1 14.5 mU/24 hrs, while 21 age-matched healthy controls had an excretion rate of 364.1 58.4 mU/24 hrs (P < 0.05). Measurements of immunoreactive kallikrein in the same urine samples demonstrated a reduction of kallikrein after long-term lithium treatment by 78%. These observations could not be attributed to changes in creatinine clearance, renal sodium or potassium excretion rates or plasma concentrations of aldosterone and vasopressin. Addition of lithium to the urine in vitro had no demonstrable effect on kallikrein measurement by amidolytic assay. We conclude that lithium in therapeutic plasma concentrations may directly suppress the secretion of kallikrein by renal connecting tubule cells

Filtration pressure response to infusion of atrial natriuretic peptides

The present experiments were undertaken to assess the effect of an atrial extract (ANF) and of the synthetic atriopeptin II (APII) on filtration pressure of rat kidneys. Continuous recordings of stop flow pressure (SFP) were made to obtain an index of the change of glomerular capillary pressure produced by atrial peptides and its time course. Short-term infusion of ANF or APII increased SFP from 40.6±0.99 to 50.7±1.42 mm Hg (p<0.001) and from 44.0±1.28 to 52.7±1.75 mm Hg (p<0.001) respectively. The maximum response was achieved promptly. Return of SFP to control was slow: 20 minutes after termination of the infusion SFP was still elevated by 4.9±1.27 mm Hg (p<0.01). Tubule and stellate vessel pressures increased less than 2mm Hg, changes that were not significant. Arterial pressure fell 6 mm Hg (p<0.05). When arterial pressure was reduced by an aortic clamp to 85–90 mmHg prior to administration of APII the response of SFP was markedly blunted (from a mean increase of 9.0±1.07 mm Hg to 4.5±0.53 mm Hg). The increase of SFP probably reflects an increase of glomerular capillary pressure. The finding suggests that atrial peptides increase glomerular filtration rate at least in part by increasing filtration pressure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47453/1/424_2004_Article_BF00586690.pd

Ornipressin in the treatment of functional renal failure in decompensated liver cirrhosis

In 11 patients with decompensated cirrhosis and deteriorating renal function, the effect of the vasoconstrictor substance 8-ornithin vasopressin (ornipressin; POR 8; Sandoz, Basel, Switzerland) on renal function, hemodynamic parameters, and humoral mediators was studied. Ornipressin was infused at a dose of 6 IU/h over a period of 4 hours. During ornipressin infusion an improvement of renal function was achieved as indicated by significant increases in inulin clearance (+65%), paraaminohippuric acid clearance (+49%), urine volume (+45%), sodium excretion (+259%), and fractional elimination of sodium (+130%). The hyperdynamic circulation was reversed to a nearly normal circulatory state. The increase in systemic vascular resistance (+60%) coincided with a decrease of a previously elevated renal vascular resistance (-27%) and increase in renal blood flow (+44%). The renal fraction of the cardiac output increased from 2.3% to 4.7% (P less than 0.05). A decline of the elevated plasma levels of noradrenaline (2.08-1.13 ng/mL; P less than 0.01) and renin activity (27.6-14.2 ng.mL-1.h-1; P less than 0.01) was achieved. The plasma concentration of the atrial natriuretic factor increased in most of the patients, but slightly decreased in 3 patients. The decrease of renal vascular resistance and the increase of renal blood flow and of the renal fraction of cardiac output play a key role in the beneficial effect of ornipressin on renal failure. These changes develop by an increase in mean arterial pressure, the reduction of the sympathetic activity, and probably of an extenuation of the splanchnic vasodilation. A significant contribution of atrial natriuretic factor is less likely. The present findings implicate that treatment with ornipressin represents an alternative approach to the management of functional renal failure in advanced liver cirrhosis

Atrial natriuretic factor

The discovery of the first well-defined natriuretic hormone, the Atrial Natriuretic Factor (ANF), has prompted research on its impact on volume regulation in health and disease. The natriuretic, diuretic, and smooth muscle-relaxing properties suggest an important role of this novel hormone in pathophysiological states with sodium or volume retention, such as congestive heart failure or cirrhosis of the liver. Investigations on the implications of ANF in liver disease have been performed for little more than 1 year, and results are still controversial in many respects. At present, it seems very likely that there is no absolute deficiency of plasma ANF in patients with cirrhosis. Moreover, elevated plasma levels in cirrhotics with ascites have been reported by several groups. However, as yet, a molecular characterization of this increased immunoreactivity is still lacking. There is disagreement on the reduced release of and renal response to ANF in subgroups of cirrhotics; however, stimulus-response-coupling might be impaired. Further studies are needed to elucidate the pathophysiological implications and therapeutical potential of ANF in patients with chronic liver disease

A METHOD FOR INDUCTION OF CHRONIC RENAL FAILURE IN RATS

Chronic Renal Disease (CRD) is a major health burden, which has recieved increased attention in recent times and has thus become one major focus of intensive research. All is agreed that the complex interplay of major pathophysiological factors that are characteristic of CRD and end stage renal failure (ESRF) is of multifactorial aetiology. However, commonly used animal models for CRD are bedeviled by methodologically induced complexities, which make the procedures not only laborious but also make interpretation of results less explicit. More often than not, some of these procedures present in addition, pathological parameters that may not universally reflect the settings of clinical forms of CRD. We have therefore characterized a simple and reproducible method for inducing chronic renal failure (CRF) in rats; in which the pathological parameters better reflect the usual findings in clinical situations. This approach has methodological and experimental advantages with respect to commonly used procedures for inducing CRF in rats, which may involve extensive renal surgery in which the renin-angiotensin system is often markedly stimulated. This later complication is at variance with clinical CRD in which low to normal renin activity is more often the rule rather than the exception. The simplicity and reproducibility of this model, coupled with a better correlation with the known features of CRF makes it a useful rat model not only for research purposes but also for testing of therapeutic maneuvers commonly used in the clinical setting