Colon kallikrein, its relation to the plasma enzyme

Localization and secretion of tissue kallikrein in peptidoglycan-induced enterocolitis in Lewis rats

The plasma kallikrein-kinin system is a mediator of intestinal inflammation induced by peptidoglycan-polysaccharide from group A streptococci (PG-APS) in rats. In this study we investigated the participation of intestinal tissue kallikrein (ITK). Lewis rats were injected intramurally with PG-APS. ITK was visualized by immunohistochemical staining. Cecal ITK concentration was measured by radioimmunoassay, and gene expression was evaluated by RNase protection assay. Kallikrein-binding protein (KBP) was evaluated in plasma by ELISA. Tissue kallikrein was identified in cecal goblet cells in both control and PG-APS-injected rats and in macrophages forming granulomas in inflamed tissues. Cecal ITK was significantly lower in acute and chronic phases of inflammation and in supernatant from in vitro cultures of inflamed cecum. ITK mRNA levels were not significantly different. Plasma KBP levels were significantly reduced in inflamed rats. The presence of tissue kallikrein in macrophages suggests participation in experimental colitis. The decrease of ITK in the inflamed intestine associated with unchanged mRNA levels suggests ITK release during intestinal inflammation.

Expression of rat kallikrein and epithelial polarity in transfected Madin-Darby canine kidney cells

Many properties of urinary kallikrein are well characterized, but the intracellular processing of prokallikrein and release by kidney cells have yet to be clarified. We report here on the synthesis of prokallikrein in Madin-Darby canine kidney (MDCK) cells transfected with rat submaxillary gland kallikrein cDNA and on its activation by MDCK cells and by an enriched liver Golgi membrane preparation. Transfected MDCK cells secreted only prokallikrein at both the apical and basolateral sides in about a 4:1 ratio, but cells transfected with kallikrein cDNA in reverse orientation or untreated cells released only traces of the enzyme. Prokallikrein, in culture medium or in homogenized MDCK cells, was fully activated by trypsin but activated only to 44% by thermolysin. Prokallikrein was synthesized and released into the medium at a high rate: the enzyme secreted by 5 x 10(6) cells in 24 hours cleaved 46 nmol/min D-Val-Leu-Arg-7-amino-4-methylcoumarin and liberated 63 ng/min bradykinin after activation. Immunocytology indicated the association of prokallikrein with the Golgi apparatus in the transfected cells. Antiserum to rat urinary kallikrein detected a single band in a Western blot of conditioned medium and also immunoprecipitated the enzyme. Aprotinin inhibited activated prokallikrein. Although MDCK cells released prokallikrein, their homogenates activated prokallikrein at both pH 5.5 and 7.5. Prokallikrein was also activated by a highly enriched liver Golgi membrane fraction and by an endoplasmic reticulum preparation, but the Golgi preparation was 38-fold more active. The activation was blocked significantly by inhibitors of serine proteases and less by cysteine protease inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence of gelatinase secretion by the submandibular gland in prepubescent rats

The gelatin cleaving activities in secretions of cultured fragments of male rat submandibular glands were studied using zymography. Gelatinolytic activities of 88-, 64-, and 57-kDa proteins detected in the tissues from 22-28-day old animals were undetectable in 31-70-day old rats. The traces of gelatinolytic activity associated with 28-kDa protein were detectable from 22-day old rats in serum-free media, and this activity of the enzyme markedly increased with aging from 38-days old. At 52-days and the subsequent stages, in addition to 28-kDa, activities associated with 60-, 32-, and 29-kDa proteins were strong. When the conditioned media were treated with 1,10-phenanthroline and diisopropyl fluorophosphate (DFP), both products inhibited activity of 88-kDa enzyme, indicating that this enzyme is Cls-like enzyme. The 64- and 57-kDa activities were inhibited by 1,10-phemanthroline, but not by DFP; when the conditioned medium of the tissue from 24-day old rats was treated with p-aminophenylmercuric acetate, gelatinolytic activity associated with 64-kDa converted to 57-kDa. Therefore, 64- and 57-kDa activities were concluded to be progelatinase A and gelatinase A, respectively. On the other hand, the gelatinolytic activities associated with 60-, 32-, 29- and 28-kDa proteins were inhibited by DFP but not by 1,10-phenanthroline, indicating that these enzymes belong to the family of serine proteinase, most probably kallikrein-related enzymes. From these findings, it was suggested that gelatinase A, along with Cls-like enzyme, participates in the maturation of the submandibular gland before it becomes active as an exocrine organ.

Purification and characterization of human salivary-gland prokallikrein from recombinant baculovirus-infected insect cells

A full-length cDNA encoding human salivary-gland preprokallikrein was inserted into the baculovirus Autographa californica nuclear polyhedrosis virus downstream of the polyhedrin promoter. The gene was expressed in transfected Spodoptera frugiperda cells and the recombinant product secreted into the culture medium. By alternating anion-exchange chromatography and gel-filtration steps, twice repeated, prokallikrein was purified to homogeneity, which was confirmed by amino acid analysis and N-terminal sequence determination. The prepropeptide was processed correctly, including the removal of the signal peptide. The resulting proenzyme was found to be glycosylated, had a molecular mass of 35 kDa and an isoelectric point of 4.6. The yield of purified recombinant protein reached a level of 5 mg/l insect cell culture. After trypsin digestion of prokallikrein, the biological activity of the released kallikrein was demonstrated by its specific amidase, esterase and kininogenase activity. The expression and purification of prokallikrein, as described here, offers the opportunity to study the proenzyme activation through protein engineering techniques in detail.

Effect of aprotinin on metastasis of Lewis lung tumor in mice

Kallikrein activity in human stomach tissue was measured and found to be about threefold higher in cancer tissue than in normal tissue. To clarify the physiological role of this tissue kallikrein, we investigated its effects on the spontaneous metastasis and tumor growth of Lewis tumors (3LL). Antiprotease, aprotinin, and gabexate mesilate (FOY) inhibited spontaneous metastasis but did not inhibit tumor growth, while tissue kallikrein and plasmin enhanced the spontaneous metastasis of 3LL. The results suggest that the inhibitory effects of aprotinin and FOY on metastasis are not only due to an inhibition of tumor cells released by tissue kallikrein, but that tissue kallikrein, a protease, also participates in metastasis. We thus conclude that aprotinin or FOY should be administered either before or immediately after operation to inhibit spontaneous metastasis.

Release of [hydroxyproline3]-kinins by tissue kallikreins of pig, rat and man

To determine the susceptibility of kininogens containing the recently described [Hyp3]-bradykinin moiety to cleavage by tissue kallikreins, we have studied the release of [Hyp3]-kinins from heat inactivated human plasma by purified tissue kallikreins. Kallikreins from man and pig were employed and compared with purified rat urinary kallikrein which is known to have a different cleavage specificity. Kinins released were separated by a modified reversed phase HPLC method and quantitated by bioassay and radioimmunoassay. Human urinary kallikrein and hog tissue kallikreins released 85-90% of the total kinins as Lys-bradykinin and 10-15% as [Hyp3]-Lys-bradykinin. In contrast, rat urinary kallikrein released 77% as bradykinin, 22% as [Hyp3]-bradykinin and negligible amounts of [Hyp3]-Lys-bradykinin from the identical substrate source indicating that rat tissue kallikreins prefer the Lys-Arg-bond within both unhydroxylated and hydroxylated kininogens. Therefore, hydroxylation of human kininogens apparently does not affect their ability to serve as substrates for tissue kallikreins with different cleavage specificities.

Kallikrein-gene expression in the rat gastrointestinal tract

The serine proteinase glandular kallikrein has been demonstrated in the gastrointestinal tract, although there is some doubt as to whether it is synthesized there or derives from exocrine-gland secretions. Using a rat pancreatic kallikrein cRNA probe we have demonstrated kallikrein-like gene expression in the corpus, duodenum, jejunum, ileum, caecum and colon, and compared the pattern of expression with that of the gastrointestinal peptides somatostatin, gastrin and glucagon. In addition, using a panel of oligonucleotide probes specific for various members of the rat kallikrein-gene family, we have shown that the kallikrein-like gene expressed appears to be expressed as true kallikrein.

Bradykinin receptors: characterization, distribution and mechanisms of signal transduction

Bradykinin is a peptide consisting of nine amino acids. It is a member of the kinin family, a class of molecules sometimes considered to be locally acting hormones. Bradykinin acts through cell surface receptors to elicit a series of biological responses, many of which have been well characterized at the whole organ or body level. However, little is known about the bradykinin receptor itself or its mechanisms of signal transduction, its function and its tissue distribution. Increasing evidence suggests that bradykinin is a member of a group of locally produced peptides which may act in a paracrine fashion as microenvironmental modulators of cell proliferation. Evidence for this derives from studies of the interaction between bradykinin and its receptor, receptor-effector coupling systems and in vitro studies of the biological effects of bradykinin. These areas, together with questions concerning the nature and number of different types of bradykinin receptors, form the main bulk of current interest in bradykinin research and are the subject of this review. The ability of bradykinin to synergize with other growth regulating ligands will also be considered.

Plasma kinin-precursor levels in clinical intestinal inflammation

Plasma kinin-precursor (kininogen) concentrations were measured in the peripheral venous blood of 7 untreated patients with inflammatory bowel diseases, 12 healthy subjects, and 5 uncomplicated fracture cases. The mean plasma kininogen levels were significantly raised (P less than 0.025) in patients with intestinal inflammation (7.0 +/- 1.0 micrograms BK Eq/ml), as compared with the value found in healthy subjects (5.7 +/- 0.7 micrograms BK Eq/ml), and in fracture cases (5.0 +/- 1.2 micrograms BK Eq/ml). The packed cell volume did not differ (P greater than 0.05) between patients and control groups. Thus, the raised plasma kininogen levels observed in patients were not the result of nonspecific changes in plasma volume. It is suggested that raised plasma kininogen might be due to increased synthesis to provide substrate for excessive kinin-formation, to a potent inflammatory agent, or to high synthesis of acute-phase reactants. The possible significance of this observation is discussed.

Bile acids and the intestinal kallikrein-kinin system

We have measured concentrations of tissue kallikrein-like amidase (TKLA) in blood-free rat gastrointestinal tissue. TKLA was present in the gut wall from the stomach to the rectum with concentration peaks in the duodenum and caecum. When rats, fasted for 24 hr were compared with normally fed animals, the mean fasted TKLA levels rose significantly in the duodenum and proximal and distal colons and fell in the caecum. No other tissues showed concentration changes. Sodium chenodeoxycholate and other bile acids have biological actions on the rat intestinal wall which are similar to those produced by the kallikrein-kinin system. We have previously reported that bile acids released TKLA from the rat colon wall. This TKLA was totally inhibited by aprotinin. We now report that intraluminal sodium chenodeoxycholate (30 mM) increases both colonic motility and colonic mucosal leakage. These increases are largely blocked by aprotinin. The ability of intraluminal sodium taurochenodeoxycholate to increase vascular leakage in the rat stomach and colon was parallelled by its ability to release TKLA from these issues. Our results are compatible with the mediation of these biological actions of the tested bile acids via activation of a serine proteinase, possibly tissue kallikrein.

Purification of human urinary prokallikrein. Identification of the site of activation by the metalloproteinase thermolysin

Human urinary active kallikrein and prokallikrein were separated on DEAE-cellulose and octyl-Sepharose columns and both purified to homogeneity by affinity chromatography, gel filtration and hydrophobic h.p.l.c. Prokallikrein was monitored during purification by trypsin activation followed by determination of both amidase and kininogenase activity. After trypsin activation, purified prokallikrein had a specific kininogenase activity of 39.4 micrograms of bradykinin equivalent/min per mg and amidase activity of 16.5 mumol/min per mg with D-Val-Leu-Arg-7-amino-4-trifluoromethylcoumarin. Purified active kallikrein had a specific activity of 47 micrograms of bradykinin/min per mg. The molecular mass of prokallikrein was 48 kDa on electrophoresis and 53 kDa on gel filtration whereas active kallikrein gave values of 46 kDa and 53 kDa respectively. Antisera to active and prokallikrein were obtained. In double immunodiffusion and immunoelectrophoresis, antiserum to active kallikrein reacted with active and pro-kallikrein. Antiserum to prokallikrein contained antibodies to determinants not found in active kallikrein, presumably due to the presence of the activation peptide in the proenzyme. Human prokallikrein can be activated by thermolysin, trypsin and human plasma kallikrein. Activation of 50% of the prokallikrein (1.35 microM) was achieved in 30 min with 25 nM-thermolysin, 78 nM-trypsin or 180 nM-human plasma kallikrein. Thus thermolysin was the most effective activator. Thermolysin activated prokallikrein by releasing active kallikrein with N-terminal Ile1-Val2. Thus human tissue (glandular) prokallikrein can be activated by two types of enzymes: serine proteinases, which cleave at the C-terminus of basic amino acids, and by a metalloproteinase that cleaves at the N-terminus of hydrophobic amino acids.

Characterization of a kininogenase from rat vascular tissue resembling tissue kallikrein

A kininogenase resembling glandular kallikrein was partially purified from vascular tissue and characterized. Saline-perfused rat tail arteries and veins were homogenized in 0.25 M sucrose containing 10 mM Tris-HCl (pH 7.4). The homogenate was centrifuged at 105,000 g for 60 minutes, and a vascular kininogenase was purified from the supernatant by chromatofocusing, affinity chromatography on immobilized antibodies against rat urinary kallikrein, and gel filtration on Sephadex G-100. The inhibitory effects of antibodies against rat urinary kallikrein were tested with equivalent kinin-forming concentrations of rat urinary kallikrein and vascular kininogenase. Kininogenase activities of both enzymes were similarly inhibited by both polyclonal and monoclonal antibodies. Aprotinin (1,000 KIU) completely inhibited vascular kininogenase activity, while soybean trypsin inhibitor (100 micrograms) did not modify its kinin-forming activity. Vascular kininogenase and rat urinary kallikrein had the same elution volume when chromatographed on a Sephadex G-100 column, and had similar mobilities in 10% polyacrylamide gel electrophoresis. Kinins released by vascular kininogenase were identified as bradykinin by reverse-phase high performance liquid chromatography. Rat vascular kininogenase appears to be similar to glandular kallikrein. Kinins released locally by vascular kininogenase may contribute to the regulation of vascular tone.

Activation of a latent kinin-generating proteinase in the porcine anterior pituitary

This study was conducted to determine whether a kinin-generating proteinase (kininogenase) previously described in the porcine anterior pituitary exists in a latent form. Porcine anterior pituitaries were homogenized in 0.25 M sucrose (pH 7.5) and sequentially centrifuged at 1000 X g for 5 min, 1500 X g for 20 min, 10 000 X g for 20 min, and 105 000 X g for 60 min. The various fractions were assayed for their ability to generate kinins from kininogen and cleave H-D-Pro-Phe-Arg-p-nitroanilide (S-2302) before or after various activation procedures. Untreated pituitary fractions had a small amount of proteolytic activity. However, large increases in kininogenase and S-2302 hydrolytic activity were observed in the 105 000 X g pellet after dialysis, or incubation with trypsin. Repeated freezing and thawing, detergents, phospholipase A2, melittin, plasmin, thrombin, urokinase and Factor Xa failed to activate kininogenase activity in the 105 000 X g pellet. However, plasmin produced massive increases in S-2302 hydrolytic activity. The kininogenase and S-2302 hydrolytic activity was sensitive to inhibition by soybean trypsin inhibitor and aprotinin, and had a broad pH optimum between 7 and 9. The data indicate that the porcine anterior pituitary kininogenase largely exists in a latent form. Also, the porcine anterior pituitary appears to contain an additional latent proteinase which can hydrolyze S-2302.

Tissue kallikrein synthesis and its modification by testosterone or low dietary sodium

A method has been developed to measure the relative rate of rat tissue kallikrein synthesis which employs a specific antiserum raised against a purified rat urinary kallikrein. Incorporation of [35S]methionine into kallikrein and protein 20 min after intraperitoneal injection was measured in submaxillary gland, pancreas, kidney and descending colon. Kallikrein content was measured with a direct radioimmunoassay, and kallikrein-specific incorporation of [35S]methionine measured after immunoprecipitation. Kallikrein specific radioactivity (c.p.m./mg of enzyme) was about 100-fold greater than that in total protein in both kidney and colon. In contrast, in pancreas the incorporation into the enzyme was only 5-fold higher than into protein, and in submaxillary gland the incorporation was equivalent. Measured as kallikrein-specific radioactivity relative to total protein radioactivity incorporated in 20 min, kallikrein represents 0.18% of total protein synthesis in the kidney, 0.34% in the pancreas, 0.41% in the colon, but 7.29% in the submaxillary gland. Dietary Na+ restriction increased the relative rate of kallikrein synthesis 1.8-fold in the kidney without a comparable effect in submaxillary gland. In contrast, testosterone increased the relative rate of synthesis 2.3-fold in submaxillary gland, but decreased it in kidney. The data show that endogenous kallikrein synthesis differs markedly in various tissues, and that interventions which are known to change kallikrein content or excretion also change the relative rate of enzyme synthesis.

Bradykinin-stimulated electrolyte secretion in rabbit and guinea pig intestine. Involvement of arachidonic acid metabolites

Bradykinin (BK) increases short-circuit current (Isc) when added to the serosal side of rabbit or guinea pig ileum or rabbit colon. Significant effects on Isc are seen at concentrations as low as 10(-10) M. Anion substitution experiments and unidirectional 36Cl flux measurements indicate that this effect of BK on Isc is due to Cl secretion. The effect of BK on Isc can be partially blocked (60-70% inhibition) by cyclooxygenase inhibitors (indomethacin and/or naproxen) and completely blocked by the phospholipase inhibitor, mepacrine. The combined cyclooxygenase/lipoxygenase inhibitors BW 755 and eicosa-5,8,11,14-tetraynoic acid (ETYA) also completely block the effect of BK on Isc but the slow-reacting substance of anaphylaxis (SRS-A) antagonist FPL 55712 has no effect. None of the above inhibitors diminish the effect on Isc of other exogenously added secretory stimuli such as vasoactive intestinal peptide (VIP), theophylline, or prostaglandin E2 (PGE2). Prior desensitization of rabbit ileum to PGE2 blocks the effect on Isc of BK but not those of VIP or theophylline. Conversely, prior desensitization of rabbit ileum to BK greatly reduces the effect of PGE2 on Isc. BK also stimulates the synthesis of PGE2 in rabbit ileal and colonic mucosa and this effect can be blocked by prior addition of either indomethacin or mepacrine. These effects of BK are similar to those of exogenously added arachidonic acid (AA). AA also stimulates Cl secretion and increases PGE2 synthesis and its effect on Isc can be inhibited by prior desensitization to PGE2 or by prior addition of indomethacin. The above results indicate that BK stimulates active Cl secretion in both small and large intestine and suggest that this effect is due to the intracellular release of AA. Although the prostaglandins appear to be the major products of AA metabolism contributing to the secretory response, lipoxygenase products may also play a role.

Pharmacological abnormality of kallikrein-kinin system in hypertension

Until recently the possible role of vasodilator systems in the etiology of hypertension has been largely ignored, although deficiency of vasodilator influence could be more important than the presence of vasoconstriction in determining vascular tone. Lower concentrations of urinary kallikrein excretion have been widely indicated in clinical and in several experimental hypertensive situations. The reduced plasma kininogen levels may reflect either decreased synthesis compensating for a chronically reduced kinin generation or genetic abnormality leading to reduced plasma kininogen, which may be a predisposing factor in hypertension. An alternative possibly could be enhanced adrenergic control during hypertensive conditions which may cause reduction in prostaglandin and kallikrein-kinin systems. It has also been suggested that most of the pharmacological actions of the kallikrein-kinin system are mediated through prostaglandin formation. Thus, subnormal kallikrein-kininogen-kinin concentrations could be the cause of reduced vasodilating influence leading to both clinical and experimental hypertension.

Kallikrein and prekallikrein of the isolated basolateral membrane of rat kidney

A basolateral membrane (BLM) enriched fraction of the homogenized rat kidney contained kallikrein and prekallikrein which differ from urinary kallikrein. Triton X-100 (0.1%) or melittin (10(-7) - 10(-5)M) solubilized the membrane-bound enzyme. Prekallikrein was activated by trypsin and plasmin. Active kallikrein and activated prekallikrein cleaved the chromogenic substrate S-2266 and released bradykinin from kininogen. Aprotinin and antiserum to rat urinary kallikrein inhibited BLM kallikrein. Gel electrophoresis separated activated BLM prekallikrein and kallikrein; prekallikrein even after activation moved slower (Rf = 0.3) in electrophoresis at an alkaline pH than active kallikrein (Rf = 1). Gel filtration resolved BLM kallikrein to two proteins of low (4 X 10(4) M) and high (1.5 X 10(5) M) molecular weight. After isoelectric focusing of the activated BLM fraction, two kallikreins with pIs of 3.9 and 5.3 were obtained. The BLM fraction also contained renin which became active after Triton treatment. Renin activity was not enhanced by trypsin or acid pH indicating that there was no prorenin present. Thus, BLM of rat kidney contains a kallikrein which is different from urinary kallikrein. This kallikrein, when released from basal membrane, may appear in renal lymph and venous effluent.

Kinins stimulate net chloride secretion by the rat colon

1 Short circuit current (SCC), transepithelial conductance and ion fluxes were measured across the isolated descending colon of the rat in response to bradykinin or kallidin. 2 Kinins added to the serosal bath caused immediate increases in SCC but were ineffective when added to the mucosal bath. Increases in SCC were accompanied by significant increases in transepithelial conductance. Threshold kinin concentration was 0.5nM and maximal increases were seen at 50-100 nM. 3 A rat glandular kallikrein (7nM) or mellitin (2 microM) also increased SCC if added to the serosal bath. 4 Responses to kinins were unaffected by mucosal amiloride (100 micron) but attenuated or blocked by serosal frusemide (100 microM), indomethacin (1 microM) or mepacrine (50 microM). 5 Replacement of chloride ion in the serosal bath by gluconate and sulphate ions abolished responses to kinins which reappeared after chloride re-addition. 6 Measurement of 36Cl, 22Na and 86Rb fluxes across the tissue showed that the kinin-induced increase in SCC resulted principally from increased net chloride secretion. Effects upon 22Na or 86Rb flux were minimal and made no contribution to the current responses observed in this tissue. 7 The results prove that kinins stimulate net chloride secretion in the rat colon, most probably via a prostaglandin-dependent pathway.

Measurement of urinary kallikrein activity. Species differences in kinin production

A sensitive, specific radioimmunoassay for kinins has been developed, which is able to detect 1.5 pg bradykinin or 3 pg lysyl-bradykinin (Lys-bradykinin). 50% displacement in the standard curve was obtained with 10 pg bradykinin or 15 pg Lys-bradykinin in 0.6-ml incubates. The antisera, raised against bradykinin, recognized well Lys-bradykinin and methionyl-lysyl-bradykinin (Met-lys-Bradykinin), but cross-reacted 0.4% or less with bradykinin fragments. Kininogen cross-reacted only 0.2%. The radioimmunoassay and kininogen from several species were used in the measurement of human and rat urinary kallikrein activity. The peptide generated by hydrolysis of the substrates by rat or human urines was characterized by radioimmunoassay in two different systems: polyacrylamide gel electrophoresis and carboxymethyl cellulose chromatography. Both urines did not produce the same kinin: the kinin produced by human urine migrated like Lys-bradykinin, whereas the kinin produced by rat urine migrated like bradykinin. This gives evidence of differences in the specificity between kinin-forming enzymes in rat and human urines.

Purification and properties of rat stomach kallikrein

Kallikrein (EC 3.4.21.8) was purified from rat stomach by column chromatography on p-aminobenzamidine-Sepharose, DEAE-Sephadex A-50 and Sephadex G-150 and by isoelectric focusing, measuring its activities to hydrolyse L-prolyl-L-phenylalanyl-L-arginine-4-methyl-coumaryl-7-amide and to release kinin from heat-treated rat plasma. the purified stomach kallikrein showed a single band on polyacrylamide gel electrophoresis at pH 7.0. Its molecular weight was calculated to be 29 000 by gel-filtration on a column of Sephadex G-50. The kallikrein was stable between pH 6-11 and hydrolyzed L-prolyl-L-phenylalanyl-L-arginine-4-methyl-coumaryl-7-amide optimally at pH 11.0. The L-prolyl-L-phenylalanyl-L-arginine-4-methyl-coumaryl-7-amide hydrolyzing activity of rat stomach kallikrein was inhibited by diisopropyl fluorophosphate and Trasylol, but not by trypsin inhibitors from soybean, lima bean and ovomucoid. These properties of rat stomach kallikrein are different from those of partially purified rat plasma kallikrein, but similar to those of glandular kallikreins from other species. From these results, it was concluded that kallikrein is present in rat stomach and that it can be classified as a glandular kallikrein.

The effect of diet on tissue levels of kinin-forming enzyme in blood-free rat gastro-intestinal tract

1. Kallikreins, kinin-forming enzymes, are present in the wall of the gastro-intestinal tract. The role of the kinin-forming system in the gut is unknown. In the present study, a modified bio-assay technique was used to detect the presence of tissue concentration gradients of kinin-forming enzyme (KFE) at different levels of the rat gastro-intestinal tract and the effect on them of diet.2. Segments of rat gut, perfused free of blood, were homogenized in 0.1 N-HCl and activated by autolytic processes. Total KFE content was then determined by incubation of extract with standard kinin-forming substrate, followed by bio-assay of the released kinin using superfused oestrous rat uterus. Acid extraction of the KFE gave a recovery of 127.4% when compared with simple water extraction.3. Tissue concentrations of KFE were determined in stomach, duodenum, jejunum, terminal ileum, caecum and proximal and distal colon. Concentrations were determined after (A) normal diet, (B) water ad libitum for 24 hr and (C) isotonic glucose ad libitum for 60 hr.4. All the gut tissues contained KFE. After diet A there was least (19.5 +/- 1.0 ng bradykinin equivalent formed per minute (KU) per gram wet weight) in the stomach and a single large peak (504 +/- 92 KU .g(-1) wet weight) in the caecum.5. The different dietary states produced changes only in the duodenum, the caecum and the distal colon. The duodenal level was raised when the organ was empty after diet B (140 +/- 29 KU .g(-1)) and fell when filled with solid or fluid after diets A (57 +/- 14 KU .g(-1)) and C (80 +/- 17 KU .g(-1)) respectively. The caecal KFE level, which was high when the lumen was full after diet A, fell progressively as it was increasingly emptied after diets B (213 +/- 41 KU .g(-1)) and C (105 +/- 42 KU .g(-1)) respectively. The KFE concentration in the distal colon was low when the lumen was full after diets A (58 +/- 10 KU .g(-1)) and B (66 +/- 17 KU .g(-1)) and rose when the lumen was nearly empty after diet C (118 +/- 17 KU .g(-1)).6. Kinin-forming activity in rat intestinal extracts had a pH optimum at pH 8.5 and formed a bradykinin-like spasmogen. The increased activity in the fasted rat duodenum was not significantly inhibited by soybean trypsin inhibitor (100 mug/ml.) while that in caeci from fed rats was inhibited by 17% (P < 0.05).7. These changes may indicate physiological involvement of the kallikrein-kinin system in these organs.

The effects of isoprenaline and bradykinin on capillary filtration in the cat small intestine

1 Lymph flow, and both lymph and plasma protein concentrations were measured in isolated, blood-perfused loops of cat ileum. 2 Permeability-surface ares (PS) products and the osmotic reflection coefficient (sigma) of the intestinal capillaries were calculated. 3 Isoprenaline (one dose) or bradykinin (two different doses) was infused into the superior mesenteric artery. 4 Isoprenaline (blood concentration about 50 ng/ml) did not affect PS or sigma. 5 Bradykinin (about 36 ng/ml) increased PS but as a sigma was unaltered, this was primarily due to an increased capillary surface area. 6 Bradykinin (about 680 ng/ml) increased PS and as sigma was reduced, there was an increased capillary permeability. 7 Reasons for the lack of effect of isoprenaline at concentrations which increase capillary filtration coefficient are discussed. 8 These data show that this technique separates drug effects on capillary surface area from effects on capillary permeability.

Rat stomach kallikrein: its purification and properties

From rat stomach, kallikrein was purified by chromatographies on columns of p-aminobenzamidine-Sepharose, DEAE-Sephadex A-50 and Sephadex G-150 and by isoelectric focusing, measuring its activities to hydrolyse prolylphenylalanyl-arginine-4-methyl-coumarine amide (Pro-Phe-Arg-MCA) and to release kinin from rat heated-plasma. The purified stomach kallikrein showed a single band on Disc electrophoresis at pH 7.0. The molecular weight of the kallikrein was calculated to be 29,000 by gel-filtration on a column of Sephadex G-50. The kallikrein was stable between pH 6 and 11 and hydrolysed Pro-Phe-Arg-MCA optimally at pH 11.0. The Pro-Phe-Arg-MCA hydrolysing activity of rat stomach kallikrein was inhibited by DFP and Trasylol, but not by trypsin inhibitors from soyabean, limabean and ovomucoid. These properties of rat stomach kallikrein was clearly distinguishable from those of partially purified rat plasma kallikrein, but similar properties to other glandular kallikreins from other species. From these results, it was concluded that kallikrein is present in rat stomach, which can be classified into glandular kallikrein.

Mobilization of colonic kallikrein following pelvic nerve stimulation in the atropinized cat

1. Pelvic nerve stimulation (p.n.s.) in cats induces atropine-resistant colonic vasodilatation and colonic contraction. The effects of this on cat colon are mimicked by synthetic bradykinin infusions. The present study examines the effect of p.n.s. on the activation of kallikrein, the kinin-forming enzyme present in colonic tissue and its effects on the plasma kinin system in the atropinized cat.2. Mean level (+/- S.D.) of mucosal kallikrein was found to be about 37 times higher in unstimulated colonic mucosa (300 +/- 100 ng bradykinin equivalents min(-1)g(-1)) than in the underlying muscle (8.2 +/- 6.3 ng bradykinin equiv min(-1)g(-1)).3. After a p.n.s. of 5 min, mean kallikrein level in colonic muscle was 7.3 +/- 3.5 ng bradykinin equiv min(-1)g(-1), which was not significantly different from the control muscle kallikrein. However, there was an 86% fall in mucosal kallikrein to 41.3 +/- 34.7 ng bradykinin equiv min(-1)g(-1) after 5 min p.n.s., indicating a rapid activation and secretion of mucosal kallikrein.4. Secretion of mucosal kallikrein was paralleled by specific depletion of plasma kininogen, the precursor of active kinin in blood draining the colon. The mean plasma kininogen level fell to 79 and 68% of the prestimulated value (3.1 +/- 1.1 S.D. mug bradykinin equiv per ml. plasma) after 5 and 10 min p.n.s. respectively. Total plasma protein and haematocrit remained unaltered excluding non-specific changes due to protein extravasation or haemodilution and indicating utilization of the plasma kinin precursor.5. Following 2 hr p.n.s., raised levels of kallikrein were detected in both colonic muscle (28 +/- 2.0 bradykinin equiv min(-1)g(-1)) and mucosa 434 +/- 118 ng bradykinin equiv min(-1)g(-1)). Preliminary studies using a kallikrein inhibitor indicated that the increased kallikrein levels originated from plasma.6. Direct stimulation of the parasympathetic pelvic nerve in the atropinized cat thus produced activation of the plasma kinin system in the colon and formation of free kinins may be responsible for the mucosal vasodilatation and strong motor contraction which is not blocked by large doses of atropine. The observation that prolonged stimulation causes extravasation of plasma kallikrein, a potential inflammatory mediator, into the tissues may be of clinical significance.

A comparison of the effects of bradykinin, 5-hydroxytryptamine and histamine on the hepatic arterial and portal venous vascular beds of the dog: histamine H1 and H2-receptor populations

1 The hepatic arterial and hepatic portal venous vascular beds of anaesthetized dogs were separately perfused in different experiments.2 From measurements of perfusion pressures and blood flows in the two series of experiments, hepatic arterial vascular resistance (HAVR) and hepatic portal venous vascular resistance (HPVR) respectively were calculated.3 Bradykinin, 5-hydroxytryptamine (5-HT) and histamine were injected intra-arterially and intra-portally and dose-response curves constructed from these data.4 Bradykinin injected intra-arterially caused dose-dependent hepatic arterial vasodilatation, and with an ED(50) of 2.66 x 10(-13) mol was more potent than any other vasodilator agent yet examined on this vascular bed.5 Bradykinin injected intraportally at doses up to 10 times those which were maximal on the arterial circuit did not alter the calculated HPVR.6 5-HT injected intra-arterially caused weak and variable rises in HAVR, indicating vasoconstriction. The maximum rise in HAVR was much less than that attained with noradrenaline in the same preparations.7 5-HT injected intraportally caused dose-dependent rises in HPVR indicating portal constriction at doses above 15-100 mug: in some experiments small doses of 5-HT resulted in reductions in calculated HPVR.8 Histamine has previously been shown to cause hepatic arterial vasodilatation: by intraportal injection, it caused dose-dependent rises in HPVR.9 In order to examine the receptors responsible for the effects of histamine, dose-response curves were constructed before and after mepyramine and metiamide.10 On the hepatic arterial vascular bed, metiamide did not antagonize the vasodilator effects of intra-arterial histamine, but these effects were antagonized by mepyramine.11 Similarly on the hepatic portal bed, the rises in HPVR due to histamine were antagonized by mepyramine but not by metiamide.12 The effects of histamine on both the hepatic arterial and portal venous vascular beds of the dog are therefore mediated predominantly by histamine H(1)-receptors.

[Bursting pressure of colon in the rats and proteinase inhibition (author's transl)]

In the early postoperative period (third postoperative day) the colonic enterotomies show 45 per cent higher bursting pressure following administration of Aprotinin than the control group (p less than 0,02). On the fifth postoperative day no difference was noted between both groups. The interpretation of the results is difficult because specific parameters such as collagen content and collagenase activity were not determinated. The relationship between colonic anastomotic breakdown and collagenase and therefore the question of collagenase inhibition have to be discussed. It is suggested that activation of procollagenase is prevented because trypsin and kallikrein are inhibited by Aprotinin.

The molecular weights of plasma and intestinal kallikreins in rats

1. The molecular weights of kallikreins of rat intestine and rat plasma have been estimated using gel filtration. 2. Extracts of pooled tissue from rat jejunum, ileum, caecum and colon activated by autolytic processes gave a single peak of kallikrein activity with a molecular weights of 33000. 3. Acid-activated rat plasma gave two peaks of kallikrein activity with molecular weight of 125000 and 61500. 4. Rat intestinal tissue contains a kinin forming enzyme having a molecular weight similar to those of glandular kallikreins and different from those of the rat plasma kallikreins.

Kinin levels in the peripheral venous blood of patients with severe vasomotor dumping before and after revisional surgery

The kinin activity in peripheral venous blood was estimated before and after jejunal interposition in 17 patients with severe vasomotor dumpling. In each case the kinin activity was assayed both under fasting conditions and after the oral administration of a liquid hypertonic glucose meal (100 g). No significant difference in the preoperative fasting kinin values was found between patients who were improved of their symptoms (11 cases) as distinct from those who did not derive any benefit from jejunal interposition (6 cases). However, in patients who obtained relief after revisional surgery, the kinin level after glucose administration (56-15 +/- 11-19 ng/ml) was significantly higher (P less than 0-01) than the release obtained in patients who were not improved by surgery (3-65 +/- 2-33 ng/ml). Furthermore, the kinin release was reduced to near normal levels on re-challenge with glucose 3 months after jejunal interposition in patients who were cured or improved of their symptoms.

Mobilization of tissue kallikrein in inflammatory disease of the colon

Colonic tissue was taken at operation from 10 patients with active ulcerative colitis and three patients with uncomplicated diverticular disease but with severe symptoms. Levels of kininogen, kallikrein, and kallikrein precursor were measured in blood-free tissue samples. In normal colon tissue a kininogen occurred in the muscle and none was detected in the mucosa. Kallikrein and its precursor were found in mucosa but not in muscle. In acutely inflamed tissue from ulcerative colitis patients relatively high levels of active kallikrein were detected in the underlying colonic muscle. There was little change in the level of kallikrein in inflamed mucosa or of kininogen in the muscle of these patients. No kallikrein was found in colonic muscle from patients with diverticular disease and the mucosal kallikrein level in these patients was unchanged. The findings suggest a mechanism for the formation of kinins in the wall of the colon which is present in ulcerative colitis but not in diverticular disease.