Purification and partial characterization of kininogenase activity from Schistosoma mansoni adult worms.

An enzyme presenting kallikrein-like activity (designated sK1) was purified from the supernatant of Schistosoma mansoni adult worm homogenate. The enzyme cleaves bradykinin from purified rat plasma kininogen. Activity was optimal at pH 9.0 and the enzyme showed amidolytic activity, since it hydrolysed the kallikrein synthetic substrate D-Pro-Phe-Arg-p-nitroanilide. The activity of sK1 upon rat plasma kininogen was strongly inhibited by the serine proteinase inhibitors phenylmethanesulfonyl fluoride, aprotinin or soybean trypsin inhibitor, but not by ethylenediaminetetraacetic acid or sodium tetrathionate. The molecular mass of sK1, as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, was 66 kDa and the pI value, estimated by analytical chromatofocusing, was 4.2. Physical and chemical properties suggest that sK1 is a serine proteinase of the kallikrein family. Evidence is presented which suggests that sK1 is a component of the tegumental surface of the parasite and the levels of its activity in the male adult worm are approximately 21 times higher than those in the female adult worm. The intravenous injection of 3 micrograms of sK1 into an anaesthetized rat induced a drastic reduction in the arterial blood pressure of the animal. This effect lasted for about 1 min, and was followed by a progressive recovery of the arterial pressure. Neither bradycardia nor cardiac arrhythmias were noticed, suggesting a peripheral vasodilation effect. The presence of sK1 on the surface of adult male worms could play an important role in the wandering capacity of coupled worms into the visceral vasculature of the host.

Pharmacological reactivity of neoplastic and non-neoplastic associated neovasculature to vasoconstrictors.

Angiogenesis and the pharmacological responses of the tumour and non-tumour associated neovasculature have been investigated. Cannulated sponge discs in mice were used to host the angiogenic stimulators, while 133Xe washout was employed to assess local blood flow. Enhancement of blood flow was detected in implants bearing B16 cells, 3T3 cells and angiotensin II (AII)-treated at day 7. The responses of non-neoplastic associated neovasculature at day 14 post sponge implantation to the vasoconstrictors used endothelin-1 (Et-1), AII, platelet activating factor (PAF) and 5-hydroxytryptamine (5-HT) were dose-dependent. By contrast, the newly formed blood vessels induced by tumour cells were markedly insensitive to the vasoconstrictors agonists Et-1 and AII, while fully responsive to PAF and 5-HT. The vessels resulting from neoplastic stimulus exhibited altered pharmacological reactivity, suggesting that the characteristics of the neovasculature are dependent on the nature of the angiogenic stimuli.

Distribution of tonin- and kallikrein-like activities in rat brain.

Tonin- and kallikrein-like activities were investigated in different regions of the rat brain. The highest values of specific tonin activity, expressed as picomoles of angiotensin II liberated per minute per milligram of protein, were found in the neurohypophysis (359 +/- 190) and in the archicerebellum (200 +/- 68). The highest level of total tonin activity (picomoles of angiotensin II liberated per minute) was observed in the archicerebellum (902 +/- 308) which retained 97% of total tonin activity of whole cerebellum. Tonin activity was not detected in the cortex of cerebellum and in the choroid plexus. Low to intermediate values of specific (1.09 +/- 0.33 to 5.32 +/- 2.37) and total (1.38 +/- 0.55 to 93.00 +/- 49.30) tonin activity were observed in adenohypophysis, cerebellar nuclei, hypothalamus, thalamus, midbrain, pons, medulla and neurohypophysis. The lowest values of specific (0.11 +/- 0.05) and total (0.69 +/- 0.31) activities were observed in the hippocampus. Kallikrein-like activity was expressed as picomoles of p-nitroaniline liberated per minute per milligram of protein. No activity was detected in the neurohypophysis. For other regions, the values of the specific activity ranged between 72 +/- 18 and 282 +/- 14 except for the choroid plexus which was 5 +/- 2. The total kallikrein activity was also homogeneous ranging from 330 +/- 100 to 1870 +/- 112. For the choroid plexus and adenohypophysis the total kallikrein activity was 2.0 +/- 0.8 and 27 +/- 11, respectively.

Sponge-induced angiogenesis in mice and the pharmacological reactivity of the neovasculature quantitated by a fluorimetric method.

Sponge-induced angiogenesis in mice and pharmacological reactivity of the neovasculature have been determined by a fluorimetric method. Pharmacokinetic studies following subcutaneous, intradermal, and intraimplant administration of sodium fluorescein resulted in a biphasic curve from which estimation of t1/2 for absorption and elimination of the dye were possible. Following topical injection of the dye at days 1, 4, 7, 10, and 14 postimplantation, measurement of fluorchrome generated emission in the systemic circulation reflected the development of blood flow in and around the implants and the interaction of the angiogenic site with the systemic circulation. The t1/2 values for the fluorescence peak in the bloodstream decreased steadily from an initial value of 6.41 +/- 0.28 min (avascular implant) to 2.78 +/- 0.23 min in fully vascularized implants (day 14). The reactivity of the neovasculature to ET-1 was dose-dependent and similar to the skin vasculature. By contrast, no reactivity to histamine was detected in the implant blood vessels, whereas it was present in the skin. These results show that the pharmacological response of the neovasculature differs from the response of mature blood vessels. The angiogenic stimulus (bFGF, 300 ng daily) decreased t1/2 for the fluorescence peak, whereas dexamethasone (1 mg/kg) increased it. Parallel histological studies corroborated the functional findings. These observations indicate the suitability of this assay to study angiogenesis, functional and pharmacological characterization of the neovasculature, and the interaction of the angiogenic site with the systemic circulation.

Angiotensin-II-induced angiogenesis in sponge implants in mice.

Stimulators of angiogenesis hold potential in promoting the development of collateral circulation in ischaemic tissue and accelerating would healing, but promote pathological vasoformation in angiogenesis-dependent diseases (solid tumours, atherosclerosis). The renin-angiotensin system is implicated in both beneficial angiogenesis and pathological vascular growth. We investigated the angiogenic activity of angiotensin II (AII) in a sponge implant model in mice; this peptide enhanced angiogenesis, as well as glycosaminoglycan (GAG, chondroitin sulfate proteoglycan) and protein synthesis in sponge matrix in mice in a dose-dependent fashion. Extensive angiogenesis was achieved with AII (1 microgram), which gave no significant increase in wet weight and protein and only a small effect on GAG. In the implants treated with AII (2 micrograms) no further increase in angiogenesis was observed, whereas a marked effect was shown in wet weight (326 +/- 15 vs. 424 +/- 27 mg), total protein (18 +/- 1 vs. 25 +/- 1 micrograms/ww) and GAG (98 +/- 10 vs. 160 +/- 13 ng/ww). The local blood flow has been determined by measuring the washout rate of 133Xe injected into the implants, correlated with histological evidence of vessel growth. This model of angiogenesis has allowed sequential studies of fibrovascular tissue infiltration simultaneously with histological and biochemical parameters of angiogenesis.

Pharmacological demonstration of a barrier for protease, peptides and acetylcholine in the endometrium of the rat.

Contractions of the rat uterus in response to trypsin, kallikrein, bradykinin, angiotensin II, oxytocin and acetylcholine, were abolished when an inside-out preparation was used. Sensitivity to Ba++, however, was preserved. In preparations in which the endometrium was mechanically removed, all above cited agonists elicited contractions. By treating the uterus with both collagenase and hyaluronidase, acetylcholine was able to induce a contraction when applied to the endometrium side of the uterus. The results show that a barrier for protease, peptides and acetylcholine is present in the mucosa of the rat uterus.

On the mechanism of rat uterus desensitization to kallikrein.

An inactive form of kallikrein prepared by iodination with cold iodine, did not show any enzymatic or oxytocic action. However, a competitive pattern between this inactive and active kallikrein was observed in rat uterus preparation: When the inactive form was applied several times in the muscle, a single dose of active kallikrein was unable to cause contraction, but a double dose elicited a response. The rhythmic movement caused by a singular dose of active kallikrein, had its time curtailed by adding the inactive kallikrein to the bath. The inactive kallikrein did not interfere with bradykinin activity.

Kallikrein-kinin system in the angiogenesis.

Using the bioassay to investigate the presence of mediators in the angiogenesis exudate to explain its property to cause vascular permeability and fall in the blood pressure we found the presence of histamine, bradykinin, prostaglandin E2 and angiotensin in the exudate. However, the role of these mediators in the angiogenesis process needs to be investigated.

Kininogenase activity of rSMT3, a rat submandibular gland tonin.

rSMT3, a tonin like angiotensin II generating enzyme present in rSMG presents a potent oxytocic effect on the isolated rat uterus, which was blocked by a B2 bradykinin receptor antagonist. Under optimal conditions of pH, rSMT3 liberates kinin at rate 19-fold greater than angiotensin II.

Tonin-like activity present in the human submandibular gland.

An enzyme which is able to liberate angiotensin II from angiotensin I, angiotensinogen(1-14) fragment and angiotensinogen was purified from human submandibular gland. Its molecular weight is 110,000; is inhibited by PMSF but not by EDTA or enalaprilat. The pH optima for angiotensin II liberation were 4.0 for angiotensin I, 7.0 for angiotensinogen(1-14) fragment and 8.0 for angiotensinogen. The total amount of angiotensin II generating activity in the human submandibular gland is 5,000-times smaller than that in the rat gland.

The action of iodinated kallikrein on the rat uterus.

Iodinated kallikrein appeared inactive on synthetic substrates, was unable to liberate kinins from rat plasma, did not cause contraction of the rat uterus and did not potentiate bradykinin activity. After several doses of iodinated kallikrein were applied to the muscle, the contraction caused by kallikrein was blocked, but the response of the preparation to bradykinin was unaltered. If a double dose of kallikrein was applied, the contraction appeared again, and the response to bradykinin was also potentiated. These results support a kinin-mediated oxytocic action of kallikrein, and suggest a new interpretation for the mechanism of kallikrein desensitization in this preparation.

Inhibition of the effects of different agonists on the rat uterus and guinea-pig ileum by Mandevilla velutina extract

O extrato de Mandevilla velutina inibe as contraçöes induzidas pela bradicinina e cininogenases (calicreína, tripsina e tonina) no útero de rata. As contraçöes por angiotensina II e mesmo por cloreto de bário também foram inibidas, quando o íleo de cobaia foi usado, a contraçäo evocada pela histamina foi inibida. Esses experimentos sugerem que a inibiçäo causada pelo extrato de Mandevilla velutina näo é seletiva para bradicinina

Rat uterine contraction by kallikrein and its dependence on uterine kininogen.

Smooth muscle responses to kallikrein (EC 3.4.21.8) are generally considered to result from kinin formation. In the present study, this premise was reexamined with respect to the isolated rat uterus. Rat submandibular gland kallikrein produced contractions of the rat uterus but the contractions disappeared after successive additions of the same dose of the enzyme to the preparation. Kallikrein-induced rat uterine contractions as well as bradykinin-induced contractions were enhanced by rat submandibular gland bradykinin potentiating factor. The incubation of kallikrein with rat uterine extract in the presence of a kininogen-depleted rat uterus produced kinin which elicited the uterine contraction. An extract from uterine horns previously depleted of kininogen was prepared. Incubation of this extract with kallikrein in a bath containing a kininogen-depleted rat uterus did not evoke uterine contraction. The incubation of four rat uterine horns with kallikrein in the presence of a uterine horn previously depleted of kininogen elicited contractions of the depleted uterus. These results suggest that the contraction produced by kallikrein involves kinin release from the uterus.

Tonin and kallikrein-kinin system.

The kininogenase activity of tonin has been demonstrated by Ikeda and Arakawa, 1984. Tonin of the rat submandibular gland contracts the rat uterus independent of addition of the substrate. On repetition, the same dose of enzyme elicited desensitization. When a double dose was used the contraction again occurred. After desensitization to tonin the contraction to kallikrein was reduced about 80% of the control. The desensitization to kallikrein lightly reduced the contraction to tonin. When the muscle was desensitized to trypsin tonin did not evoke contraction. These experiments suggest the presence of two different substrates in the uterus, one more specific to kallikrein and the other for tonin. The experiments with the parallel uterus preparation strongly suggest release of kinin in the process of contraction of the uterus by tonin.

Crossed desensitization between plasma kallikrein and trypsin.

The addition of rat plasma kallikrein or trypsin to the bath containing rat uterus caused contraction. On repetition, the same amount of the enzyme, after 4-5 additions, elicited desensitization. When a double dose of the enzyme was used the contraction again occurred. However, after desensitization to kallikrein the response for trypsin remained in altered, but after the desensitization for trypsin the uterus did not respond to kallikrein. Chymotrypsin, in spite of did not cause contraction, became the uterus insensitive to kallikrein and trypsin. It seems that bradykinin is not involved in the mechanism of contraction. The desensitization may be due to the release of inhibitors specific for kallikrein or trypsin; the effect of chymotrypsin may also be due to release of similar inhibitors.

Effect of purified scorpion toxin (tityustoxin) on the pancreatic secretion of the rat.

Intravenous injection, in anesthetized rats, of a single dose of purified scorpion toxin (tityustoxin, TsTX), obtained from the venom of the Brazilian scorpion Tityus serrulatus, causes a striking increase in flow rate, protein content, kallikrein and amylase activities of the pancreatic juice. The flow rate and protein content of the juice remain significantly higher than in control rats, for at least one hour, whereas the kallikrein activity returns to control values 30 min after tityustoxin injection. Sub-diaphragmatic bilateral vagotomy does not prevent the pancreatic secretion induced by tityustoxin; moreover, vagotomy potentiates the flow rate and kallikrein secretion produced by the toxin. Pre-treatment of the rats with atropine blocks the pancreatic secretion evoked by tityustoxin. It is suggested that the pancreatic secretion induced by tityustoxin is due to actions of acetylcholine, released from postganglionic nerve fibers, on muscarinic receptors. The mechanism by which vagotomy potentiates the pancreatic secretion evoked by tityustoxin is under investigation.