Secretagogue-induced changes in system A amino acid transport in the rat exocrine pancreas: stimulation of 2-methylaminoisobutyric acid efflux by carbachol

Secretagogue-induced changes in exocrine pancreatic amino acid transport are poorly understood. In this study uptake of the specific non-metabolized System A amino acid analogue 2-methylaminoisobutyric acid (2-MeAIB) was measured in the isolated perfused rat pancreas during 60 min loading with D-[3H]mannitol (extracellular tracer) and 2-[14C]MeAIB. Tracer 2-MeAIB reached a maximal uptake of 37 +/- 4% (n = 4) after 3 min of loading and gradually decreased to a steady-state uptake of 13 +/- 1%. Infusion of carbachol (3.10(-7) M) during the tracer loading period abolished net tracer 2-MeAIB uptake, and reperfusion in the absence of carbachol restored net uptake to the prestimulus value. Less than 41% of the arterial 2-[14C]MeAIB or D-[3H]mannitol activity appeared in the basal pancreatic secretion. Carbachol evoked a 4.8-fold increase in pancreatic juice flow and appeared to reduce the activity of both tracers in the exocrine secretion. During washout of the pancreas with an isotope-free medium 2-[14C]MeAIB cleared from a rapidly exchanging pool with a time constant (tau 1) of 1.4 +/- 0.3 min (n = 4) and a more slowly exchanging pool with a time constant (tau 2) of 20.7 +/- 1.1 min. Carbachol accelerated efflux of 2-[14C]MeAIB from the epithelium but had no effect on the slow phase of D-[3H]mannitol washout. Our findings suggest that activation of cholinergic receptors modifies Na+-dependent System A amino acid transport in the basolateral membrane of the exocrine pancreatic epithelium.

Nasal challenge with cold, dry air induces a late-phase reaction

Nasal challenge of susceptible persons with cold, dry air (CDA) (breathing air at a temperature of -7 to -10 degrees C and a relative humidity of 0 to 10% at a flow rate of 12.5 ml/min for 15 min) stimulates nasal symptoms and release of histamine and other mediators associated with mast-cell activation. To investigate whether such a nonantigenic stimulus induces a late-phase reaction (LPR) in the nose, we challenged 12 preselected volunteers who had previously shown an immediate response to CDA. We monitored the subjects' responses for 10 h by means of symptom diaries and the levels of histamine and TAME-esterase activity in nasal lavage fluids. All 12 subjects showed an immediate response, whereas 8 had a LPR, as indicated by a recurrence of symptoms (rhinorrhea and congestion) hours later, accompanied by an increase in the levels of histamine and TAME-esterase activity. Rhinorrhea and congestion were concomitant with the late reelevation of mediators. Control challenges of these subjects with warm, moist air (WMA), as well as serial nasal lavages without any stimulation of the nose, failed to induce an early- or a late-phase response. The amount of both mediators and symptoms generated during the 10 h after the initial reaction to CDA challenge was significantly greater (p less than 0.02) than after WMA challenge or after performance of nasal lavages without a challenge. The ability of CDA to induce a LPR strengthens the connection between initial mast-cell activation and the occurrence of a LPR.

Prostaglandin D2 and histamine during the immediate and the late-phase components of allergic cutaneous responses

With a skin blister technique in which the mediators generated by the trauma of forming the blister are allowed to subside, we have collected human interstitial skin fluid during the course of allergic reactions to ragweed, and measured levels of histamine and prostaglandin D2 (PGD2). Of 18 ragweed-allergic individuals tested, 11 developed both an immediate and a late-phase reaction (LPR) with fivefold-elevated levels of histamine (40 ng/ml) at 30 minutes and a peak level of PGD2 (6.5 ng/ml) later at 2 1/2 hours after ragweed challenge. The other seven allergic individuals had immediate reactions without an LPR lesion and demonstrated somewhat smaller elevations of histamine (25 ng/ml) but much lower levels of PGD2 (1.6 ng/ml; p less than 0.05). The time course of appearance of these mediators was identical in both groups of patients. The fluids from unchallenged blisters of allergic and nonallergic patients and the fluids of nonallergic patients challenged with ragweed had similar levels of histamine, at the lower limit of detection, and undetectable PGD2 levels. The peak levels of PGD2 in allergic individuals correlated with the size of the LPR lesion (p less than 0.05). These data suggest that the LPR involves the secondary elaboration of mediators different from mediators responsible for the immediate manifestations of the allergic skin reaction.

Simplified assessment of fine aerosol distribution in human airways

We characterized homogeneity of bronchopulmonary distribution of a 0.9% saline aerosol with a mass median aerodynamic diameter (MMAD) of 1.12 micron (sigma g = 2.04) labeled with [99mTc]sulfur colloid in nine normal subjects and nine patients with asthma. Aerosol distribution was quantified from frequency distribution histograms generated from Anger camera scans. Skew (a measure of histogram asymmetry) and kurtosis (a measure of histogram range) were significantly elevated (p less than 0.05) in the asthma patients with 0.68 +/- 0.30 and 2.62 +/- 0.81, respectively, compared with 0.39 +/- 0.12 and 1.89 +/- 0.18, respectively, in the normal subjects. Skew and kurtosis were significantly correlated with baseline forced expiratory volume in 1 sec (FEV1, an index of airway obstruction) with rs = -0.4799 (p less than 0.05) and -0.5929 (p less than 0.01), respectively. Skew and kurtosis were also significantly correlated with mucociliary clearance after approximately 90 min (an index of large, central airway deposition) with rs = 0.6801 and 0.6373, respectively (p less than 0.01). This simplified method of analysis does not require additional study days or procedures and facilitates the detection of airflow obstruction in asthma.

Studies on the allergic and nonallergic nasal inflammation

Nasal lavage after antigenic and nonantigenic nasal stimulation has become an important tool for the study of inflammatory phenomena in the upper airway. Biochemical and cytologic information is relatively easily obtainable, and pharmacologic manipulations can be readily monitored. This article is of several studies aiming toward a more profound understanding of the mechanisms of allergic and nonallergic rhinitis by the use of laboratory-challenge procedures and nasal-lavage techniques. An early and a late reaction are detected clinically in the nose after antigen challenge of allergic individuals. In addition, the sensitivity to antigen significantly increases after the initial challenge, and this phenomenon is not obligatorily linked to the presence of a late-phase reaction (LPR). Inflammatory mediators, mostly mast cell- and/or basophil-derived, are detected in the nasal washes and correlate with the symptomatology in both the early and the late reactions. The allergen-induced LPR is marked by an early influx of eosinophils and, later, basophils and neutrophils. Elevation of major basic protein and histamine, but not prostaglandin D2, is detected during the LPR, giving evidence of active eosinophil and basophil participation. Systemic steroids can effectively suppress the clinical, biochemic, and cellular manifestations of antigen-induced LPR. Topical steroids have a similar effect but are also capable of suppressing the early reaction to antigen. A nonallergic form of rhinitis can be induced in the laboratory by nasal inhalation of dry air at freezing temperatures in individuals who report sensitivity to cold and windy environments.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunotherapy for nasal allergy

Controlled studies establish the effectiveness of immunotherapy for allergic rhinitis related to grasses, ragweed, mountain cedar, and birch pollens. Clinical improvement appears to be specific, to require adequate dosage, and to relapse once booster injections are discontinued. Specific immunologic responses increase blocking IgG antibodies in serum and secretions, blunt IgE responses, and reduce lymphocyte reactions. Immediate mediator release is reduced both in basophils challenged in vitro and in nasal secretions after local challenge in vivo. Effects on late-phase inflammatory reactions are still under investigation. Standardization of allergenic extracts by immunologic methods should make useful therapeutic responses more frequent.

The osmolality of nasal secretions increases when inflammatory mediators are released in response to inhalation of cold, dry air

Inhaling cold, dry air nasally induces in some persons symptoms of rhinitis that are associated with an increase in the level of mast-cell-associated mediators in nasal lavages. The present study, directed at understanding the mechanism of this reaction, showed that 9 subjects who displayed symptoms and inflammatory mediator release had significant (p less than 0.01) increments in nasal fluid osmolality, whereas the osmolality of the fluids of 6 subjects unaffected by cold, dry air challenge did not differ from baseline. Significant correlations were found between the mediator concentration and the osmolality of recovered nasal lavages (rs = 0.617, p less than 0.02; rs = 0.679, p less than 0.01 for histamine and TAME-esterase(s), respectively). No changes in the osmolality of nasal secretions were found in atopic subjects undergoing nasal challenge with antigen, despite the generation of symptoms and significant elevations in the levels of inflammatory mediators in their nasal lavages. Because increasing the osmolality of the medium surrounding isolated mast cells in vitro triggers mediator secretion, these observations support the concept that the response to cold, dry air nasal inhalation is caused by the release of mediators secondary to an increase in the osmolality of the mucosal secretions.

Fasting, refeeding and diabetes modulate free amino acid concentrations in the rat exocrine pancreas: role of transstimulation in amino acid efflux

The effects of fasting, refeeding, and streptozotocin-induced experimental diabetes on free amino acid concentrations in the rat exocrine pancreas were investigated. Extracts of pancreatic tissue and plasma were analyzed using high-performance liquid chromatography (HPLC). Pancreatic and plasma concentrations of alanine were reduced in animals fasted for 24 to 72 h. Pancreatic concentrations of leucine, arginine, and glutamine were increased after fasting for 48 h, and concentrations of all essential amino acids plus the nonessential amino acids glycine, serine, taurine, and glutamine were elevated after fasting for 72 h. Refeeding 72 h fasted animals for 3 h or 24 h had a negligible effect on the plasma amino acid concentrations, but markedly lowered the concentration of essential amino acids within the pancreatic tissue. Diabetes lowered the total plasma amino acid concentration from 4.9 mM to 3.1 mM but increased the total pancreatic tissue amino acid level from 16.4 mM to 18.3 mM. Efflux of intracellular amino acids into the circulation of the isolated perfused pancreas was assessed under basal conditions and in response to a vascular amino acid challenge using HPLC. L-serine transstimulated efflux of a large number of amino acids, whereas cellular efflux was only minimally affected by L-phenylalanine. Fasting and diabetes-induced increases in essential amino acid concentrations within the pancreas may reflect decreased protein synthesis, accelerated protein catabolism, or a change in membrane transport. Altered intracellular amino acid levels may directly regulate exchange diffusion of intracellular for extracellular amino acid(s).

Effect of short-term systemic glucocorticoid treatment on human nasal mediator release after antigen challenge

The effect of systemic glucocorticoid treatment on early- and late-phase nasal allergic reactions after allergen challenge was determined in a double-blind, cross-over study in 13 allergic individuals. The subjects were pretreated for 2 d before challenge with 60 mg prednisone per day or a matching placebo. A previously described model using repeated nasal lavages for measuring mediator release in vivo was utilized. Symptom scores obtained repeatedly before, during, and after the challenge and the number and timing of sneezes were recorded. The mediators measured were histamine. N-alpha-p-tosyl-L-arginine methyl ester (TAME)-esterase activity, kinins, PGD2, and LTC4/D4. Albumin was also measured as a marker of plasma transudation. Blood samples were taken for determination of total number of white blood cells, differential count, and total blood histamine content. No effect of steroid therapy was found on the appearance of symptoms or any of the mediators, except a reduction in kinins, in the early phase of the allergic reaction. However, in the late phase, the prednisone reduced the number of sneezes (P less than 0.01), as well as the level of histamine (P less than 0.05), TAME-esterase activity (P less than 0.05), kinins (P less than 0.05), and albumin (P less than 0.05). Only low levels of leukotrienes were found in the late phase, but the quantities of these mediators seemed to be decreased by the glucocorticoid treatment (P = 0.06). PGD2 did not increase during the LPR and thus was not affected by glucocorticosteroids. The immediate response to a second challenge 11 h after the first was also evaluated. Whereas the appearance of mediators was enhanced over the initial response to the same challenge dose in placebo-treated subjects, this enhancement was abrogated after prednisone treatment. As this dose of drug is known to be clinically effective in treating hay fever, the present study confirms the earlier findings of others that short-term systemic glucocorticoid treatment inhibits the late phase but not the immediate phase of antigen challenge. Furthermore, secondary enhancement of immediate responses is inhibited. This study shows that glucocorticoids inhibit the generation or release of inflammatory mediators during the late reaction and the physiologic response.

The effect of a histamine synthesis inhibitor on the immediate nasal allergic reaction

We studied the effect of alpha-fluoromethyl histidine, an irreversible histamine synthesis inhibitor, on the immediate nasal reaction to antigen challenge in a double-blind, placebo controlled, randomized, parallel study using 13 subjects. The patients received either active drug 100 mg twice daily or placebo, for 3 weeks. A nasal allergen challenge was performed before and after at weekly intervals. Symptoms at challenge were assessed and the levels of histamine, TAME-esterase activity and kinins were measured in nasal lavages before and after antigen challenge. Skin tests were also performed at weekly intervals. In addition, the urinary excretion of the main histamine metabolite, telemethylimidazole acetic acid, was measured before and after 3 weeks of treatment. The active treatment induced 60% reduction in histamine levels in the lavage fluids before and after antigen challenge, as well as a reduction in the histamine levels in the lavage fluids before and after antigen challenge, as well as a reduction in the main urinary histamine metabolite. However, no reduction was found in nasal symptoms obtained after antigen challenge. The levels of kinins and TAME-esterase activity were not significantly reduced.

The prevalence of indoor allergens in the Baltimore area: house dust-mite and animal-dander antigens measured by immunochemical techniques

Mattress dust samples from 42 homes in Baltimore, Md., were analyzed by ELISA and rocket immunoelectrophoresis (RIE) for major excrement allergens (P1 [equal to Dp 42], Df 6, and Dm 6) of house dust mites, Dermatophagoides pteronyssinus, D. farinae, and D. microceras, by RIE for cat major epithelial allergen (cat Ag 1) and horse major epithelial antigen (horse Ag 11), and by counter-current immunoelectrophoresis (CCIE) for cat and dog antigens. Dp 42 was detected by ELISA in 24 samples (57%) and Df 6 in 39 samples (92%). All samples were negative to Dm 6. Recorded levels varied from 50 ng of allergen per gram of dust (detection limit) to 15,000 ng/gm. A combined content of Dp 42 and Df 6 greater than 700 ng/gm was associated with a positive reaction in RIE. Concentrations of Dp 42 and Df 6 did not correlate (rS = 0.21; p greater than 0.05). Cat and dog antigens were frequently detected by CCIE (77% and 63%, respectively). CCIE titer to cat correlated well with quantitation of cat Ag 1 by RIE (p less than 0.01). Horse antigen was detected in few homes (5%). None of the specific allergen determinations correlated with levels of human serum albumin determined by RIE.

Inhibition of mediator release in allergic rhinitis by pretreatment with topical glucocorticosteroids

Patients with allergic rhinitis often have immediate symptoms after antigen challenge (the early-phase response), followed several hours later by a recurrence of symptoms (the late-phase response). Systemic glucocorticosteroids are known to inhibit the late-phase but not the early-phase response. We studied the effect of one week of pretreatment with topical (rather than systemic) glucocorticosteroids on the response to nasal challenge with antigen in a double-blind, randomized, placebo-controlled crossover study of 13 allergic patients who had previously had a dual response to nasal challenge. The patients were challenged with three 10-fold increments of allergen, producing an early response, and were then followed for 11 hours, encompassing the late response, before they were rechallenged with the lowest dose of allergen. We monitored their responses by means of symptom scores and measurements of the levels of histamine, tosyl-L-arginine methyl ester (TAME)-esterase activity, and kinins in nasal lavages. Topical glucocorticosteroids significantly reduced both the symptoms and the levels of histamine, TAME-esterase activity, and kinins in the early, late, and rechallenge allergic reactions. The fact that, in contrast to treatment with systemic glucocorticosteroids, prolonged pretreatment with topical glucocorticosteroids inhibited the early-phase response to antigen suggests that the route and duration of administration affect the mechanisms of action of the steroids. We conclude that inhibition of the early-phase as well as the late-phase response by topical glucocorticosteroids may provide an advantage over treatment with systemic glucocorticosteroids in patients with allergic rhinitis.

Ionic dependence of amino-acid transport in the exocrine pancreatic epithelium: calcium dependence of insulin action

Rapid unidirectional transport (15 sec) of L-serine and 2-methylaminoisobutyric acid (MeAIB) was studied in the isolated perfused rat pancreas using a dual-tracer dilution technique. Time-course experiments in the presence of normal cation gradients revealed a time-dependent transstimulation of L-serine influx and transinhibition of MeAIB influx. Transport of the model nonmetabolized System A analog MeAIB was Na+ dependent and significantly inhibited during perfusion with 1 mM ouabain. Although transport of L-serine was largely Na+ independent, ouabain caused a time-dependent inhibition of transport. Influx of both amino acids appeared to be inhibited by the ionophore monensin but unaffected by a lowered extracellular potassium concentration. Removal of extracellular calcium had no effect on influx of the natural substrate L-serine, whereas stimulation of transport by exogenous insulin (100 microU/ml) was entirely dependent upon extracellular calcium and unaffected by ouabain. Paradoxically, exogenous insulin had no effect on the time-course of MeAIB influx. The characteristics of L-serine influx described in earlier studies together with our present findings suggest that insulin may modulate the activity of System asc in the exocrine pancreatic epithelium by a calcium-dependent mechanism.

Arachidonic acid metabolites during nasal challenge

In order to assess the role of arachidonic acid metabolites in the early reaction to antigen, we challenged six allergic individuals with and without premedication with aspirin and recorded their clinical response, as indicated by number of sneezes, and measured the levels of inflammatory mediators. The early reaction to antigen was associated with increases in the levels of histamine, N-alpha-tosyl-L-arginine methyl esterase (TAME-esterase) activity, prostaglandin (PG) D2, leukotriene C4, PGE, and thromboxane. Aspirin significantly inhibited the increases in the cyclooxygenase metabolites PGE, PGD2, PGF2 alpha, 6-keto-PGF1 alpha, and thromboxane but did not affect the amount of sneezing or the levels of histamine, TAME-esterase activity, or leukotrienes. The pattern of the metabolites and their response to pretreatment with aspirin parallel the response of purified human lung mast cells, supporting the notion that the early phase of allergic rhinitis is a mast cell-dominated event.

Theophylline reduces histamine release during pollen-induced rhinitis

In an attempt to understand how theophylline achieves its in vivo therapeutic effect, a double-blind crossover study of the effect of theophylline on the immediate response of the upper airways to challenge with antigen was performed. Ten subjects with allergic rhinitis were challenged with increasing doses of antigen extract, and their responses were assessed by counting the number of sneezes and measuring the level of histamine, N-alpha-p-tosyl-L-arginine-methyl ester-esterase activity, and kinin in nasal secretions. One-week premedication with theophylline led to serum levels in the therapeutic range (8 to 21 micrograms/ml). There were significant reductions in both the physiologic response to antigen challenge and the appearance of mediators in secretions after drug administration as compared to placebo. These data suggest that theophylline, at therapeutic blood levels, achieves at least part of its in vivo efficacy by reducing the release of histamine and other mediators from mast cells/basophils.

Transport characteristics of system A in the rat exocrine pancreatic epithelium analyzed using the specific non-metabolized amino acid analogue alpha-methylaminoisobutyric acid

The selectivity and kinetics of system A amino acid transport in the rat exocrine pancreatic epithelium were characterized using the specific analogue alpha-methylaminoisobutyric acid. Unidirectional influx of alpha-methylaminoisobutyric acid was measured in isolated perfused pancreata by rapid dual tracer dilution. In cross-inhibition experiments DL-methylalanine, L-serine, L-cysteine, glycine, L-phenylalanine and L-glutamine were effective inhibitors of influx, whereas L-glutamate and L-lysine were less effective. In the presence of sodium alpha-methylaminoisobutyric acid influx was saturable with an apparent Kt = 1.7 +/- 0.2 mM and Vmax = 0.49 +/- 0.03 mumol/min per g (mean +/- S.E., n = 6). Influx of alpha-methylaminoisobutyric acid at 50 microM and 100 microM concentrations was significantly inhibited as the perfusate sodium concentration was gradually decreased from 156 mM to 26 mM by isoosmolar choline replacement. Estimated Kt values for sodium at these two methylaminoisobutyric acid concentrations approximated 200 mM. System A activity in the basolateral membrane of the exocrine pancreatic epithelium exhibits a high transport affinity, a wide tolerance for different amino acids and a dependency upon the extracellular sodium concentration.

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.

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.

Dose of cat (Felis domesticus) allergen 1 (Fel d 1) that induces asthma

In 10 patients with cat asthma and hay fever, we quantified the doses of cat allergen (expressed as cat allergen 1 [Cat-1] in log Food and Drug Administration [FDA] units) inspired from the ambient air of a room containing living cats required to induce a 20% drop in FEV1. These doses were compared with the doses required to cause the same change in FEV1 when the patients were subjected to bronchial challenge with aerosols of cat hair and dander extract in the conventional manner. Patients highly sensitive to cat extract by skin, leukocyte histamine release, and bronchoprovocation tests and with measurable levels of anticat IgE by RAST were exposed for up to 2 hours in a room occupied full-time by two cats. At the same time, room air was sampled by a Durham gravity sampler, by an Andersen sampler, and by lapel fiberglass filters. When hair and dander particles trapped on greased slides by gravity and Andersen samplers were stained, sized, and counted, squamous cell fragments in the less than 10 mm range were abundant. Assays of extracts from the lapel filters for Cat-1 content by radioimmunoassay and for allergenic activity by leukocyte histamine release demonstrated a significant correlation (p less than 0.05) between the results of the two assays. All patients developed rhinitis and asthma during exposure. At the time of a 20% drop in FEV1, when air sampling was stopped, the lapel filters had trapped a total of -1.86 to less than -3.04 (median -2.74) log FDA units Cat-1. These measurements of Cat-1 exposure in the room correlated (p less than 0.01) with the doses of cat extract (-1.18 to -3.15 [median -2.26] log FDA units Cat-1 equivalents) required to induce a 20% fall in FEV1 in the conventional bronchoprovocation tests.