Nasal glandular secretory response to cholinergic stimulation in humans and guinea pigs.

A guinea pig model of nasal secretory responses was developed to assess the contributions of vascular permeability and glandular secretion responsible for the production of cholinergically stimulated nasal secretions. The nasal secretory responses to provocation with saline, methacholine, and atropine on the ipsilateral (challenged) side and contralateral (reflex) side were analyzed by measurement of total protein (Lowry method), guinea pig albumin (enzyme-linked immunosorbent assay), 125I-labeled bovine serum albumin after intravenous injection, and alkaline phosphatase enzyme activity in nasal fluid. Alkaline phosphatase was found to be localized to submucosal glands by zymography. Topical methacholine challenge increased the secretion of total protein, alkaline phosphatase activity, and albumin on the ipsilateral challenged side, whereas the percentage of total protein represented by albumin was not increased. This response was totally prevented by atropine pretreatment. Serial provocation with methacholine resulted in progressively reduced amounts of both the total protein and alkaline phosphatase in secretions. The observation that repeated challenges produced progressively smaller responses was also examined employing human nasal provocation. Repeating methacholine (25 mg) challenges four times at 10-min intervals in six human volunteers revealed that the initial challenge produced the largest response as reflected in total protein, albumin, lysozyme, lactoferrin, immunoglobulin (Ig) G, IgA, and secretory IgA secretion. When the constituents in secretions were analyzed in relationship to the total protein, the two vascular proteins, IgG and albumin, demonstrated the greatest decrements with repeated methacholine challenges. The glandular proteins, lactoferrin, lysozyme, and secretory IgA, either remained constant or increased in their relative proportion to total protein. Thus, cholinergic stimulation causes glandular secretion from both the guinea pig and human nasal mucosa.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma kallikrein during experimentally induced allergic rhinitis: role in kinin formation and contribution to TAME-esterase activity in nasal secretions

We have shown recently that kinins are generated during experimentally induced allergic rhinitis in man, and have demonstrated that substrates for kinin-forming enzymes are provided during the allergic response by a transudation of kininogens from plasma into nasal secretions. In light of this increased vascular permeability during the allergic reaction, we have extended our studies on the mechanisms of kinin formation to examine the potential involvement of plasma kallikrein. Allergic individuals (n = 7) and nonallergic controls (n = 7) were challenged intranasally with an allergen, and nasal lavages, obtained before and after challenge, were assayed for immunoreactive human plasma kallikrein/prekallikrein (iHPK). Post-challenge iHPK values were significantly elevated (p less than 0.01) in the allergic group (353 +/- 394 ng/ml; x +/- SD) as compared to the nonallergics (19 +/- 22 ng/ml), and correlated with increases in kinins, histamine, and N-alpha-tosyl-L-arginine methyl esterase (TAME-esterase) activity and with the onset of clinical symptoms. Gel filtration studies revealed that plasma prekallikrein is activated during the allergic response and contributes to kinin formation prior to interaction with plasma protease inhibitors. We also show that the majority of the TAME-esterase activity detected in nasal secretions during the allergic response is due to activities consistent with a plasma kallikrein/alpha 2-macroglobulin complex and with mast cell tryptase.     

Concentrations of glandular kallikrein in human nasal secretions increase during experimentally induced allergic rhinitis

We have previously demonstrated that a mixture of bradykinin and lysylbradykinin is generated in nasal secretions during the immediate allergic response to allergen. The present studies were performed to determine whether glandular kallikrein plays a role in kinin formation during the allergic reaction. Allergic individuals (n = 7) and nonallergic controls (n = 7) were challenged intranasally with appropriate allergen, and nasal lavages obtained before and after challenge were assayed for immunoreactive glandular kallikrein as well as for histamine, kinins, and N-alpha-tosyl-L-arginine methyl esterase (TAME-esterase) activity. The increase in postchallenge immunoreactive glandular kallikrein levels above baseline was significantly greater (p less than 0.01) for the allergic group (16.3 +/- 14 ng/ml; means +/- SD) than for the nonallergic controls (1.0 +/- 1.9 ng/ml). Increased levels of immunoreactive glandular kallikrein correlated with increases in kinins, histamine, and TAME-esterase activity and with the onset of clinical symptoms. Characterization of immunoreactive glandular kallikrein purified from postchallenge lavages by immunoaffinity chromatography confirmed the identity of this material as an authentic glandular kallikrein on the basis of its inhibition by protease inhibitors and by monospecific antibody to tissue kallikrein, its chromatographic behavior on gel filtration, and its ability to generate lysylbradykinin from highly purified human low m.w. kininogen. The specific activity of this purified material, in terms of kinin generation from kininogen, was very similar to that for authentic glandular kallikrein, suggesting that most if not all of the immunoreactive material purified from nasal lavages represented active enzyme. Inhibition studies by using pooled postchallenge lavages suggest that the majority of the kinin generating activity in these samples was due to glandular kallikrein. We conclude, therefore, that glandular kallikrein is secreted during the allergic response and can contribute to the formation of the lysylbradykinin produced during the allergic reaction.     

Relationship between histamine and physiological changes during the early response to nasal antigen provocation

Toinvestigate the temporal relationships of mediator release andphysiological changes during the early response to allergen, wechallenged allergic individuals intranasally with antigen and followedtheir responses. This was done by using small filter paper disks tochallenge one nostril and collect secretions from both the challengedand the contralateral nostril, thus enabling us to evaluate thenasonasal reflex. There was a significant increase insneezing after allergen challenge that peaked within 2 min and returnedto baseline. The weights of nasal secretions as well as nasal symptomsincreased immediately and remained significantly elevated for 20 min inboth nostrils. Nasal airway resistance increased slowly, reaching itspeak at ~6 min after challenge on the ipsilateral side, but it didnot change on the contralateral side. Histamine levelspeaked 30 s after removal of the allergen disk on the side ofchallenge, whereas albumin levels peaked after those of histamine.Lactoferrin paralleled the increase in secretion weights and occurredin both nostrils. Increasing doses of antigen produced dose-dependentincreases in all parameters, whereas control challenges produced noresponse. These studies describe a human model for the evaluation ofthe allergic response that is capable of simultaneously measuringmediator release and the physiological response, including thenasonasal reflex. This model should prove useful instudying the mechanism of allergic rhinitis in humans.     

Hyperosmolar saline induces reflex nasal secretions, evincing neural hyperresponsiveness in allergic rhinitis.

We investigated whether hyperosmolar saline (HS), applied via paper disk onto the septum of one nostril, induces a nasal secretory response. Furthermore, we examined whether this response is accentuated in patients with active allergic rhinitis (AR) compared with healthy volunteers. Unilateral HS produced significant nasal secretions both ipsilateral and contralateral to the site of challenge in the AR group and only ipsilaterally in the healthy group. The HS-induced nasal secretions were significantly greater in the AR vs. the healthy subjects. In a separate study, we ascertained that the nasal response to HS is neurally mediated and found that ipsilateral nerve blockade with lidocaine significantly attenuates the HS-induced secretions bilaterally. In another group of AR subjects, we determined whether nociceptive fibers were involved in this response and found that sensory nerve desensitization with repeated application of capsaicin attenuated the HS-induced nasal secretions. Finally, we determined whether the secretory hyperresponsiveness in AR is attributable to increased reactivity of submucosal glands rather than of nerves. We found that the dose response to methacholine, which directly stimulates the glands, was identical among AR and healthy subjects. We conclude that, in AR, nasal challenge with HS induces significantly greater reflex secretions involving capsaicin-sensitive nerve fibers, consistent with the notion of neural hyperresponsiveness in this disease.     

Limb vasodilation provoked by stimulation of the carotid sinus. Importance of histaminergy in the dog

The vasodilator reflex induced by baroreceptor stimulation was studied on the hindlimbs of the dog. The reflex was induced by norepinephrine (1 microgram/kg) either by intravenous injection or by direct injection into the carotid sinus. In other experiences, the baroreceptor stimulation was obtained by distension of the sinus by rapid injection of 100 ml of physiological serum. The vascular response was studied by recording the hindlimbs blood flow. One of the limbs was previously pretreated by mepyramine and cimetidine (blockage of histaminergic H1 and H2 receptors). During the first minute after the baroreceptor stimulation, blood samples were collected from the venous blood of hindlimbs for histamine assay (fluorometric assay). Our results show: a much lower vasodilation on the limb pretreated by histamine antagonist, a significant increase during the reflex vasodilation of histamine blood levels measured in the efferent blood of hindlimbs. These results, obtained in experimental conditions as physiological as possible (blood perfusion of the limbs with "natural" hemodynamic parameters) permit to conclude that the vasodilation induced by baroreceptor reflex is at least partially histaminergic in the dog.     

Histamine-containing cells obtained from the nose hours after antigen challenge have functional and phenotypic characteristics of basophils.

The pattern of mediators and appearance of cells that stain with alcian blue during human experimental early and late phase allergic reactions suggest that basophils accumulate in nasal secretions within hours of local Ag stimulation. To further explore whether the histamine containing cells that enter the nose after Ag challenge are mast cells or basophils, we studied their functional and phenotypic characteristics. Approximately 24 h after intranasal Ag provocation of subjects with allergic rhinitis, nasal lavage was performed, and the cells were isolated for degranulation studies, analysis of surface Ag, and viability. The average histamine content per alcian blue staining cell was 0.78 +/- 0.2 pg (n = 7), similar to that reported for peripheral blood basophils. Nasal cells were challenged in vitro with anti-IgE, ragweed Amb a I, and FMLP and their responses were compared to those of peripheral blood basophils isolated simultaneously from the same donors. Nasal leukocytes released histamine maximally at 0.1 micrograms/ml of anti-IgE (35.8 +/- 7.8%, n = 7) and responded to FMLP (25.4 +/- 9.9%, n = 7). The response of the cells to ragweed Amb a I and anti-IgE was attenuated compared to peripheral blood basophils. Anti-IgE-induced histamine release was calcium and temperature dependent. Dual color immunofluorescence and flow cytometric analysis of the recovered nasal cells coexpressed CD18, a leukocyte marker not expressed by mast cells. The nasal cells consistently had high levels of spontaneous histamine release (19.5 +/- 2.0%, n = 22). The viability of all cells, assessed by erythrosin B dye exclusion, was 70 +/- 2% (n = 15). However, the viability of IgE-bearing cells was only 28.3 +/- 5.7% (n = 4). The characteristics of histamine release and the nature of the cellular surface markers provide functional proof that the histamine-containing cells accumulating after nasal Ag challenge are basophils and not mast cells.     

May nasal hyperreactivity be a sequela of recurrent common cold?

Respiratory viral infections may worsen bronchial hyperreactivity. However, there is no data on the possible role of recurrent infectious rhinitis in nose hyperreactivity. This study was therefore designed to investigate whether subjects suffering from recurrent common cold have nasal hyperreactivity, assessed by histamine nasal challenge. This study included a group of 40 patients (19 males, mean age 34.1 years) with history of at least five episodes of common cold in the previous year, but without documented allergy, and twenty healthy subjects (8 males, mean age 32.3 years) were enrolled as control group, all of whom were non-allergic. Nasal provocation test with histamine was performed in all subjects. Nasal provocation test with histamine induced a 200% increase in nasal resistance after provocation in 24 (60%) patients suffering from recurrent viral rhinitis. No normal subject had an increase >180% in nasal resistance. There was a significant difference between the patient group and the control group (p<0.05). In conclusion, this study shows that nasal hyperreactivity might be a sequela of recurrent common cold. Further studies should be conducted to confirm this preliminary finding.     

Neuropeptide Y is a vasoconstrictor in human nasal mucosa.

Neuropeptide Y (NPY) is a neurotransmitter in sympathetic nerve fibers in human nasal mucosa. Like norepinephrine, NPY acts as a vasoconstrictor. An established method of nasal provocation was used to determine the effects of topically applied NPY on nasal resistance to airflow measured by anterior rhinomanometry, the protein content of nasal secretions, and the protein content of bradykinin-induced secretions. NPY (2.3 nmol) reduced the resistance to inspiratory airflow by 57 +/- 18% (P < 0.001) in 10 normal subjects and by 50 +/- 17% (P < 0.05) in 12 subjects with perennial rhinitis. In nasal provocations, NPY in doses of 0.1-10 nmol had no effect on vascular (albumin), glandular (lysozyme, glycoconjugate), or total proteins present in lavaged nasal secretions. Because the vasoconstrictor properties of NPY may only be apparent in the presence of increased vascular permeability and albumin exudation, bradykinin (BK) nasal provocation was performed. BK (500 nmol) significantly increase total protein (10- to 20-fold), albumin (10- to 30-fold), and glycoconjugate (2- to 5-fold) in lavage fluid. NPY (2.3 nmol) reduced BK-induced total protein by 59 +/- 15% (P < 0.05) and albumin by 63 +/- 17% (P < 0.02) but had no significant effect on glandular secretion. Therefore exogenous administration of NPY to the human nasal mucosa reduced nasal airflow resistance and albumin exudation without affecting submucosal gland secretion. NPY agonists may be useful for the treatment of mucosal diseases characterized by vasodilation, vascular permeability, and plasma exudation.     

不同手术方式治疗慢性鼻-鼻窦炎对上颌窦黏膜纤毛传输功能的影响

目的:比较不同手术方式治疗慢性鼻-鼻窦炎的疗效及其对上颌窦黏膜纤毛传输功能的影响,为临床制定治疗慢性鼻-鼻窦炎的优选术式提供参考依据。方法:选取2013年9月-2014年12月于本院耳鼻咽喉科就诊的160例确诊为慢性鼻-鼻窦炎的患者作为研究对象,将其随机分为4组,分别为治疗组1~4,每组各60例。治疗组1接受上颌窦自然开口扩大术,治疗组2接受上颌窦开窗术,治疗组3接受经泪前隐窝上颌窦开放术,治疗组4接受上颌窦口球囊扩张术。观察和比较4组患者的术后鼻腔黏膜的覆盖、水肿、囊泡形成、骨质暴露、瘢痕形成等情况,上颌窦窦腔内分泌物性状、蓄积情况以及术后3个月和6个月时行上颌窦腔糖精实验及窦口周黏膜活检情况。结果:四组手术后均取得较好临床疗效,而组4的临床总有效率显著高于其他三组(均P0.05)。术后3、6个月,组4Lund-Kennedy评分和MMT时间均明显低于其他三组(均P0.05);在上颌窦黏膜活检方面:术后炎性细胞数量及状细胞和黏膜下腺体细胞形态及黏膜下结构水肿改善程度亦在中组四最为显著(P0.05)。结论:上颌窦窦球囊扩张术治疗慢性鼻-鼻窦炎疗效较高,可有效改善状细胞和黏膜下腺体细胞形态及鼻窦黏膜水肿、窦口通畅引流等作用,且安全性高。     

黑水国遗址汉代人群的上颌窦炎症

上颌窦是位于鼻腔周围最大的骨质腔,由于其所处位置及结构的特殊性,相比额窦、筛窦、蝶窦,上颌窦更容易受到感染产生炎症反应,因此上颌窦炎是现代社会最常见的炎症性疾病之一。通过对黑水国遗址汉代人群上颌窦的观察,发现该墓地中有40.5%的个体上颌窦内出现骨形态的改变,以穗状骨片为主。女性上颌窦炎出现率远高于男性,但无统计学上的显著差异,男性上颌窦炎左侧出现率高于右侧,女性右侧高于左侧。按照不同的年龄段划分,从未成年期到中年期上颌窦炎的出现率随着年龄的增长而增长,但是通过二元逻辑回归检验,发现上颌窦炎与年龄之间并无统计学上的显著意义。在患有上颌窦炎的个体中,有66.7%的个体都出现了牙周病,一半以上的个体出现了龋齿。这似乎预示着上颌窦炎与牙齿疾病之间有着一定的联系。张掖黑水国遗址汉代人群上颌窦炎的高出现率可能是多因素导致的结果,包括寒冷干燥的气候环境、空气污染、牙齿疾病以及病原微生物等。     

Relevance of histamine and tryptase concentrations in nasal secretions after nasal challenges with phosphate buffered saline and allergen

In this prospective study, a quantitative determination of histamine and tryptase in nasal secretions after nasal phosphate buffered saline (PBS) and allergen challenge was performed in 18 atopic patients who were compared with ten non-allergic healthy volunteers. The aim of the study was to determine the normal and pathological concentrations of these important mediators in nasal secretions. The second objective was to test the relevance of these two mast cell secreted mediators after nasal challenge. Results showed that the concentrations of tryptase in almost all samples were under the minimal detection limit (< 0.5 muU/g) and only a sigrtificant increase of tryptase (median, 28 muU/g) occurred immediately after nasal allergen challenge in the patient group. Histamine concentration significantly increased after every nasal PBS challenge (median, 69 ng/g after first PBS challenge and 165 ng/g after second PBS challenge) in the control group, as well as in the patient group after both PBS (median, 69 ng/g) and allergen (median, 214 ng/g) challenge. On the other hand, a rapid onset of sneezing and increase in nasal airway resistance was experienced only in the patient group after nasal allergen challenge, but did not occur after PBS challenge even though the histamine concentrations significantly increased in both groups. This study suggests that tryptase is a more preferable marker than histamine in quantitative monitoring of mast cell activation especially during the early phase nasal allergic reaction.     

Platelet-activating factor: an inflammatory mediator in the acute phase of allergic conjunctivitis in a guinea-pig model

The role of platelet-activating factor (PAF) as a mediator of increased conjunctival vascular permeability was investigated in a guinea-pig model of immediate hypersensitivity. Vascular permeability of the conjunctiva was determined by measuring the albumin content in lavage fluid (LF) after topical challenge with either PAF or ovalbumin. PAF produced a dose-dependent increase of the vascular permeability within minutes. Topical pretreatment with levocabastine, a potent histamine H(1)-antagonist demonstrated no effect towards the vascular permeability in response to PAF provocation. Pretreatment with eyedrops containing the specific PAF antagonist BN 52021 (1%) showed a significant inhibition of the vascular permeability (60.2%) and the clinical score (27.5%) after PAF challenge. In sensitized guinea-pigs, levocabastine showed a marked inhibition of both the vascular permeability (80.5%) and the clinical score (70%) after topical challenge with ovalbumin. BN 2021, although to a lesser extent, showed a similar effect towards the vascular permeability (26.8%) and the clinical score (28%) after antigen provocation. When BN 52021 and levocabastine were administered in combination, the vascular permeability was significantly decreased after antigen challenge in comparison with eyes pretreated with levocabastine alone. These results indicate that PAF plays a role in the acute phase of allergic conjunctivitis in the guinea-pig.     

Effect of capsaicin on nasal secretion in anesthetized ferrets.

In urethan-anesthetized ferrets, we investigated the nasal response to capsaicin infused via a catheter inserted retrogradely into the lingual artery. Capsaicin dose-dependently increased fluid output from the nose (nasal fluid output) and the lateral nasal gland (glandular fluid output). The secretory response to capsaicin (80 nmol/kg ia) was completely blocked by atropine and hexamethonium, indicating that a cholinergic reflex mediates capsaicin-induced nasal hypersecretion in this model. The amount of nasal secretions collected as nasal fluid output was similar to that collected as glandular fluid output, indicating that the lateral nasal gland contributes significantly to this increase in nasal secretions induced by intra-arterially administered capsaicin. In addition, the nasal fluid output had a higher protein concentration and osmolality than the glandular fluid output. This finding suggests that the gland is not the sole site of action of capsaicin on the nasal secretory response. It is likely that capsaicin also increases microvascular permeability, thereby contributing further to the alteration in the nasal secretions. Finally, repeated subcutaneous injections of capsaicin significantly reduced the secretory response to capsaicin, indicating the development of desensitization in vivo. These results support the role of capsaicin-sensitive sensory nerves in mediating a secretory response in the ferret nose.     

Suppression of pulmonary and systemic vascular histamine H2-receptors in allergic sheep

We have previously demonstrated a depression of airway H2-receptor function in sheep allergic to Ascaris suum antigen. To investigate whether this is a generalized defect, we studied the H1- and H2- histamine receptor functions in the pulmonary and systemic circulations of allergic and nonallergic sheep. Pulmonary arterial pressure, and cardiac output were measured for calculation of pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR) before and immediately after a rapid intrapulmonary infusion of histamine (10 micrograms/kg), with and without pretreatment with H1- (chlorpheniramine) and H2- (metiamide) antagonists. Histamine alone increased mean PVR to 435 and 401% of base line and decreased mean SVR by 51 and 54% in the nonallergic and allergic sheep, respectively (P less than 0.001). In the nonallergic sheep following pretreatment with chlorpheniramine (selective H2 stimulation) or metiamide (selective H1 stimulation), histamine decreased SVR by 18 and 36%, respectively, suggesting that approximately two-thirds of the vasodepressor response was mediated by H1-receptors and one-third by H2-receptors. Combined H1- and H2-antagonists completely blocked the histamine response. In allergic sheep the histamine-induced decrease in SVR was primarily mediated by H1-receptors, because the response was blocked by H1-antagonist, chlorpheniramine, and the H2-antagonist, metiamide, had no effect. In the pulmonary circulation selective H1-stimulation caused a similar increase in PVR in allergic (365%) and nonallergic sheep (424%), whereas selective H2-stimulation caused a significant decrease in PVR in the nonallergic group (14%) but not in the allergic group.(ABSTRACT TRUNCATED AT 250 WORDS)     

New ways to go—nasal floor structures as channelling system for vomeronasal stimuli in the shrew (<Emphasis Type="Italic">Sorex araneus</Emphasis>, Mammalia)

The mammalian lateral nasal gland (LNG, also called Steno’s gland) is known to be one source of so-called odorant-binding proteins, which are suggested to work as vehicles to carry chemosensory stimuli within the nasal cavity in order to guide them to olfactory and vomeronasal sensory neurons. Up to now, a largely unattended and unanswered question is how the secretions of the LNG migrate between the glandular opening at the upper edge of the anterior lateral nasal wall and the more caudally located vomeronasal organ. In order to address this issue, the functional morphology of the rostral nasal cavity of Sorex araneus was investigated histologically. Special interest was laid on the opening region of the LNG in the vestibular region of the nose and its topological connection to a hitherto largely unnoticed nasal concha, the atrioturbinate. It appears that the atrioturbinate serves as a specialised channel that directs the secretions of the LNG pointedly towards the entrance of the vomeronasal organ. In addition, it was observed that—contrary to previous reports—the LNG in Sorex araneus is anatomically clearly separated from the maxillary sinus gland and does not invade the maxillary sinus.     

Clinal variation of maxillary sinus volume in Japanese macaques (Macaca fuscata)

Macaques (genus Macaca) are unique among cercopithecids in that they possess a maxillary sinus, and among anthropoids in that they demonstrate a relatively weak relationship between the size of this sinus and the cranium. To test the hypothesis that extrinsic factors may contribute to maxillary sinus size variation, a sample of 46 Japanese macaque (M. fuscata) crania from known localities were subjected to computed tomography (CT) imaging, and sinus volume and nasal cavity area were analyzed relative to latitude and temperature variables. The results suggest that the environmental factors are significant determinants of nasal cavity size in Japanese macaques, but that the relationships between the environment and maxillary sinus volume (MSV) are probably a passive consequence of changes in the size of the nasal cavity. The sinus shrinks as the nasal cavity expands, due to an increased need to condition inspired air in colder climates. This in turn suggests that the sinus itself does not contribute significantly to upper respiratory function.     

Kinin metabolism in human nasal secretions during experimentally induced allergic rhinitis

We have previously shown that both bradykinin and lysylbradykinin are generated in nasal secretions upon nasal challenge of allergic individuals with appropriate allergen and have suggested that these potent pro-inflammatory peptides may contribute to the pathogenesis of the allergic response. In this study we used a variety of synthetic substrates together with both thin layer and high performance liquid chromatography systems to examine the metabolism of these peptides in nasal secretions obtained by lavage. We now demonstrate that in addition to low levels of angiotensin-converting enzyme, nasal lavages contain an aminopeptidase activity that converts lysylbradykinin to bradykinin, and a carboxypeptidase that removes the C-terminal arginine from bradykinin and lysylbradykinin. The levels of all these activities are significantly increased after allergen challenge of allergic, but not nonallergic, individuals. The aminopeptidase and carboxypeptidase activities present in post-challenge lavages from allergic individuals convert lysylbradykinin to intermediate products (bradykinin and des (Arg10) lysylbradykinin) and eventually to des (Arg9) bradykinin. The nasal carboxypeptidase was activated 475% by 0.1 mM CoCl2 and was inhibited by the carboxypeptidase N inhibitor, MERGETPA (D-L-mercaptomethyl-3-guanidino-ethylthiopropanoic acid) (IC50 = 10 microM). The aminopeptidase activity was not affected by MERGETPA but was potently inhibited by amastatin and bestatin (IC50 = 0.05 microM and 3.0 microM, respectively). The activity of the aminopeptidase against its synthetic substrate was also inhibited by lysylbradykinin (IC50 = 50 microM). Both the carboxypeptidase and aminopeptidase activities had neutral pH optima and were inhibited by o-phenanthroline, but were unaffected by inhibitors of neutral endopeptidases (phosphoramidon) or angiotensin-converting enzyme (Captopril). The Km of bradykinin for the nasal carboxypeptidase was 139 +/- 14 microM (n = 3). We conclude that during the allergic response, nasal secretions contain aminopeptidase and carboxypeptidase activities that convert lysylbradykinin and bradykinin (B2 agonists) to des (Arg9) bradykinin (a B1 agonist). Because the nature of the kinin receptors in the nasal mucosa are currently unknown, it remains to be determined whether this metabolism results in the termination of biologic activity or the production of a biologically active moiety.     

Refractoriness for ultrasonically nebulized distilled water and histamine after histamine challenge

Refractoriness for bronchial provocation frequently occurs after different challenge tests used to assess bronchial hyperresponsiveness in asthmatic patients. We investigated whether histamine inhalation could cause refractoriness for bronchoconstriction induced by ultrasonically nebulized distilled water (UNDW) and whether histamine causes tachyphylaxis for a subsequent histamine challenge in nine stable asthmatic patients. Preinhalation of histamine induced a significant diminished bronchoconstrictor response to UNDW cumulative dose of inhaled UNDW causing a 20% fall in forced expired volume in 1 s. The mean increased from 3.5 +/- 0.8 to 11.8 +/- 2.6 (SE) ml after histamine challenge (P less than 0.01). However, repeated inhalation of histamine did not change the bronchoconstrictor response to histamine within 1 h after rechallenge (P greater than 0.5). The magnitude of refractoriness for UNDW inhalation after preinhalation of histamine was correlated to the bronchoconstrictor response to histamine (r = 0.73, P less than 0.05). We conclude that inhaled histamine can induce refractoriness for UNDW, which seems to be related to the degree of bronchial hyperresponsiveness.     

Vagal inhibitory effects on peripheral circulation in acute coronary occlusion.

The reflex adjustments of the peripheral circulation in response to acute coronary occlusion were studied in anesthetized dogs with isolated vascular beds perfused at constant flow. Coronary occlusion caused significant increases in perfusion pressure which averaged 27 +/- 4 mmHg in the hindlimb, 19 +/- 8 mmHg in skeletal muscle, and 13 + 5 mmHg in the mesenteric artery. These responses were less than half those caused by a similar decrease in aortic pressure obtained with hemorrhage. Coronary occlusion caused no significant changes in renal and paw circulations, while marked vasoconstriction resulted from hemorrhage. When aortic pressure was maintained constant throughout the duration of coronary occlusion, there was a significant vasodilatation in all beds studied. After vagotomy, coronary occlusion caused a constrictor response similar in magnitude to that caused by hemorrhage in each vascular bed and the dilator responses to occlusion at constant aortic pressure were abolished. Both constrictor and dilator changes were prevented by alpha-adrenergic blockade. Mechanical distension of the left ventricle in four dogs with carotid sinus nerves cut caused a significant reflexdilatation in the hindlimb. Thus, coronary occlusion initiates an inhibitory reflex mediated by vagal afferents which opposes peripheral vasoconstriction most effectively in the renal and paw circulations.