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Topic:Histamine
Histamine is an organic compound involved in various physiological processes in horses, including immune response, gastric acid secretion, and neurotransmission. It is synthesized from the amino acid histidine and is stored in mast cells and basophils, which release histamine in response to allergens or tissue injury. In horses, histamine plays a role in allergic reactions and inflammatory responses, influencing conditions such as equine asthma and urticaria. The compound interacts with specific histamine receptors, which mediate its effects on target tissues. This page compiles peer-reviewed research studies and scholarly articles that explore the synthesis, function, and clinical implications of histamine in equine health.
Effects of dexamethasone and hydroxyzine treatment on intradermal testing and allergen-specific IgE serum testing results in horses. To determine whether dexamethasone or hydroxyzine affect intradermal testing (IDT) and allergen-specific IgE serum testing (ASIST) results in horses, these tests were performed serially in five horses without signs of atopic dermatitis before and after treatment with the drugs. IDT consisted of saline, histamine (1:100,000 w/v) and eight commercial extracts; results were evaluated as subjective scores by comparison to saline (0) and histamine (4) and as objective measurement of wheal diameter (mm). After baseline testing, dexamethasone (20 mg) was administered intramuscularly daily for 7 days....
In vitro bioassay to detect reaginic antibodies from the serum of horses affected with recurrent airway obstruction. In horses, Recurrent Airway Obstruction (RAO) is an allergic disease that involves IgE mediated Type I Hypersensitivity responses. The development of this type of allergy involves a series of events that begins with reaginic antibodies, mainly IgE and some IgG subclasses. These reaginic antibodies bind with high affinity, via the Fc portion, to FcepsilonRI receptors on the membrane of mast cells and basophils. Once bound, environmental allergens cross-link the antibodies, which results in mast cell degranulation leading to the production of histamine and other chemical mediators that act toget...
Sensitization of skin mast cells with IgE antibodies to Culicoides allergens occurs frequently in clinically healthy horses. IgE antibodies are mediators of mast cell degranulation during allergic diseases. The binding of IgE to its high-affinity IgE receptor on mast cell surfaces is called "sensitization" and precedes the development of clinical allergy. Previously, intradermal injection of anti-IgE or the anti-IgG(T) antibody CVS40 induced immediate skin reactions in horses. This suggested that both IgE and IgG(T) sensitize equine skin mast cells. Here, we investigated sensitization to allergen and with IgE or IgG(T) in clinically healthy horses of different age groups. In addition, immediate skin reactions to Cul...
Reproducibility of airway responsiveness in horses using flowmetric plethysmography and histamine bronchoprovocation. Inflammatory airway disease has a high prevalence in horses, but is often a diagnostic challenge. Flowmetric plethysmography and histamine bronchoprovocation (FP/HBP) is a simple and effective tool for diagnosis, but reproducibility of these measurements made over time has not been established. Objective: We hypothesize that the measurement of airway responsiveness in horses using FP/HBP is consistent over both short and long periods of time. Methods: Twenty-nine healthy adult horses from 2 university herds. Methods: In this prospective experimental study, airway responsiveness was determined ...
A histamine release assay to identify sensitization to Culicoides allergens in horses with skin hypersensitivity. Skin hypersensitivity is an allergic disease induced in horses by allergens of Culicoides midges. The condition is typically diagnosed by clinical signs and in some horses in combination with allergy testing such as intradermal skin testing or serological allergen-specific IgE determination. Here, we describe an alternative method for allergy testing: a histamine release assay (HRA) that combines the functional aspects of skin testing with the convenience of submitting a blood sample. The assay is based on the principle that crosslinking of allergen-specific IgE bound via high-affinity IgE rec...
Identification, expression and characterisation of a major salivary allergen (Cul s 1) of the biting midge Culicoides sonorensis relevant for summer eczema in horses. Salivary proteins of Culicoides biting midges are thought to play a key role in summer eczema (SE), a seasonal recurrent allergic dermatitis in horses. The present study describes the identification, expression and clinical relevance of a candidate allergen of the North American midge Culicoides sonorensis. Immunoblot analysis of midge saliva revealed a 66 kDa protein (Cul s 1) that was bound by IgE from several SE-affected (SE+) horses. Further characterisation by fragmentation, mass spectrometry and bioinformatics identified Cul s 1 as maltase, an enzyme involved in sugar meal digestion. A c...
Histamine bronchoprovocation does not affect bronchoalveolar lavage fluid cytology, gene expression and protein concentrations of IL-4, IL-8 and IFN-gamma. In diagnosing inflammatory airway disease (IAD) in performance horses, a histamine bronchoprovocation (HBP) test is often performed. In previously published studies, HBP is usually undertaken prior to cytological examination of the bronchoalveolar lavage (BAL) cells. The purpose of this study was to determine if HBP alters (1) the total nucleated cell numbers and distribution in BAL fluid (BALF) and (2) the mRNA and protein concentrations of selected cytokines in BAL cells and BALF, respectively. BALF was initially collected endoscopically from the right middle or diaphragmatic lung lobe in ei...
Evaluation of a new premedication protocol for administration of equine rabies immunoglobulin in patients with hypersensitivity. The present study was undertaken to standardize skin testing and to develop a safe and effective premedication protocol for administration of ERIG in those with skin test positivity/hypersensitivity. Methods: A method of grading of skin testing was developed using injection histamine as a positive control. This was evaluated by using it on 517 subjects who had severe (WHO category III) exposure to rabies. A premedication protocol consisting of injections pheniramine, ranitidine, hydrocortisone and adrenaline was evaluated by using it on fifty one subjects who were skin test positive/hypersensi...
Role of intracellular kinases in the regulation of equine eosinophil migration and actin polymerization. Inappropriately activated eosinophils can contribute to disease pathogenesis and intracellular signalling pathways that regulate functional responses may represent a therapeutic target. Little is known about intracellular signalling in equine eosinophils and this study examined the role of phospholipase C (PLC) and a range of protein kinases on responses to histamine and CCL11. Histamine (10(-4) M) or CCL11 (5.6 x 10(-9) M)-induced actin polymerization, migration and superoxide production by eosinophils from healthy horses were compared in the presence and absence of selective kinase inhibitor...
Comparison of cellular and humoral immunoassays for the assessment of summer eczema in horses. The objective of this study was to compare and analyze three common diagnostic methods for summer eczema (SE) in horses, an allergic dermatitis caused by bites of Culicoides spp. Nine horses with a medical history of SE and nine control animals were intradermally challenged with whole body extracts (WBE) and the saliva of a native (C. nubeculosus) and exotic (C. sonorensis) Culicoides species. Blood and serum samples of the horses were examined for basophil reactivity by a histamine release test (HRT) and for Culicoides-specific serum immunoglobulin E (IgE) and G (IgG) by enzyme-linked immunos...
Cetirizine in horses: pharmacokinetics and pharmacodynamics following repeated oral administration. The pharmacokinetics of the histamine H(1)-antagonist cetirizine and its effect on histamine-induced cutaneous wheal formation were studied in six healthy horses following repeated oral administration. After three consecutive administrations of cetirizine (0.2 mg/kg body weight, bw) every 12h, the trough plasma concentration of cetirizine was 16+/-4 ng/mL (mean+/-SD) and the wheal formation was inhibited by 45+/-23%. After four additional administrations of cetirizine (0.4 mg/kg bw) every 12 h, the trough plasma concentration was 48+/-15 ng/mL and the wheal formation was inhibited by 68+/-11%....
Cetirizine in horses: pharmacokinetics and effect of ivermectin pretreatment. The pharmacokinetics of the histamine H(1)-antagonist cetirizine and the effects of pretreatment with the antiparasitic macrocyclic lactone ivermectin on the pharmacokinetics of cetirizine were studied in horses. After oral administration of cetirizine at 0.2 mg/kg bw, the mean terminal half-life was 3.4 h (range 2.9-3.7 h) and the maximal plasma concentration 132 ng/mL (101-196 ng/mL). The time to reach maximal plasma concentration was 0.7 h (0.5-0.8 h). Ivermectin (0.2 mg/kg bw) given orally 1.5 h before cetirizine did not affect its pharmacokinetics. However, ivermectin pretreatment 12 h be...
Plethysmographic comparison of breathing pattern in heaves (recurrent airway obstruction) versus experimental bronchoconstriction or hyperpnea in horses. Horses with recurrent airway obstruction (heaves) are described as exhibiting "increased abdominal effort," but it is unknown whether this translates to an effective contribution to ventilation. Objective: We hypothesized that heaves is characterized by asynchrony between rib cage and abdominal motions, and that the abdominal component is the major contributor to ventilation. Methods: The rib cage versus abdominal motion in naturally occurring heaves (n = 15) was compared to controls at rest (n = 7) and during hyperpnea because of lobeline treatment, and the effects of histamine-induced bronch...
Reactivity of equine airways–a study on precision-cut lung slices. A study was performed to evaluate the use of precision-cut lung slices (PCLS) for studies on the contraction of equine airways. Lungs of 10 horses were taken to prepare PCLS of approximately 250 microm from equine lung tissue using a special microtome. The lung slices were cultured and the enclosed small airways were monitored using a microscope with coupled digital camera, which was used to determine the airway luminal area and diameter from digital images. As indicated by the beating of the ciliated epithelium and reactivity of airways on methacholine challenge, the tissue slices were found ...
Early onset airway obstruction in response to organic dust in the horse. Equine recurrent airway obstruction (RAO) has been used as a naturally occurring model of human asthma. However, it is unknown whether there is an early-phase response in RAO. The aim of this study was to determine whether exposure to organic dust induces immediate changes in lung function in RAO-affected horses, which could be mediated by airway mast cells. Six RAO-affected horses in remission and six control horses were challenged with hay-straw dust suspension by nebulization. Total respiratory resistance at 1 Hz, measured by forced oscillation, was increased from 0.62 +/- 0.09 cmH(2)O.l(-1...
Fexofenadine in horses: pharmacokinetics, pharmacodynamics and effect of ivermectin pretreatment. The pharmacokinetics and the effects on inhibition of histamine-induced cutaneous wheal formation of the histamine H1-antagonist fexofenadine were studied in horse. The effect of ivermectin pretreatment on the pharmacokinetics of fexofenadine was also examined. After intravenous infusion of fexofenadine at 0.7 mg/kg bw the mean terminal half-life was 2.4 h (range: 2.0-2.7 h), the apparent volume of distribution 0.8 L/kg (0.5-0.9 L/kg), and the total body clearance 0.8 L/h/kg (0.6-1.2 L/h/kg). After oral administration of fexofenadine at 10 mg/kg bw bioavailability was 2.6% (1.9-2.9%). Ivermect...
Improvement of the lung function of horses with heaves by treatment with a botanical preparation for 14 days. The effects of an oral preparation containing a mixture of extracts from yellow gentian, garden sorrel, cowslip, verbena and common elder on the lung function of nine horses suffering from heaves were determined in a longitudinal crossover study. The horses were divided at random into a group of five (group 1) and a group of four (group 2). The horses in group 1 were each given 15 tablets of the preparation twice daily, while the horses in group 2 were left untreated. Fourteen days later, the horses in group 2 were given the same course of treatment while the horses in group 1 were left untrea...
Evaluation of the precision of intradermal injection of control substances for intradermal testing in clinically normal horses. To evaluate the precision of intradermal testing (IDT) in horses. Methods: 12 healthy adult horses. Methods: IDT was performed on the neck of each horse by use of 2 positive control substances (histamine and phytohemagglutinin [PHA]) and a negative control substance. An equal volume (0.1 mL) for each injection was prepared to yield a total of 20 syringes ([4 concentrations of each positive control substance plus 1 negative control substance] times 2 positive control substances times 2 duplicative tests) for each side of the neck. Both sides of the neck were used for IDT; therefore, 40 syringes...
Comparison of results for intradermal testing between clinically normal horses and horses affected with recurrent airway obstruction. To evaluate differences in response to ID injection of histamine, phytohemagglutinin (PHA), and Aspergillus organisms between clinically normal horses and horses with recurrent airway obstruction (RAO). Methods: 5 healthy adult horses and 5 adult horses with RAO. Methods: Intradermal testing (IDT) was performed on the neck with 2 positive control substances (histamine and PHA) and a mixture comprising 5 Aspergillus species. Four concentrations of each test substance plus a negative control substance were used. Equal volumes (0.1 mL) of each test substance were prepared to yield 15 syringes ([4...
Protein kinase C (PKC) isotype profile in eosinophils from ponies with sweet itch and role in histamine-induced eosinophil activation. Eosinophils have been implicated in the pathogenesis of the seasonal equine allergic skin disease, sweet itch. Protein kinase C (PKC) is involved in regulating eosinophil function and antigen challenge has been reported to alter PKC isotype expression in blood eosinophils from allergic human subjects. Here we have compared the pattern of PKC isotype expression in eosinophils from sweet itch ponies with that in cells from normal ponies both during the active and inactive phases of the disease. A role for PKC in histamine-induced eosinophil activation was also investigated. Conventional PKCs alp...
Gastric ulceration in an equine neonate. A 24-hour-old colt presented with clinical signs consistent with gastric ulceration. Treatment was initiated with a histamine type-2 receptor antagonist and clinical signs resolved. Gastroscopy at 16 d confirmed the presence of a gastric ulcer. Although gastric ulceration is common in foals, it is rarely reported in foals this young.
Pharmacokinetics and pharmacodynamics of clemastine in healthy horses. Clemastine is an H1 antagonist used in certain allergic disorders in humans and tentatively also in horses, although the pharmacology of the drug in this species has not yet been investigated. In the present study we determined basic pharmacokinetic parameters and compared the effect of the drug measured as inhibition of histamine-induced cutaneous wheal formation in six horses. The most prominent feature of drug disposition after intravenous dose of 50 microg/kg bw was a very rapid initial decline in plasma concentration, followed by a terminal phase with a half-life of 5.4 h. The volume of d...
Arterial hypoxemia in exercising thoroughbreds is not affected by pre-exercise nedocromil sodium inhalation. It has been reported that pulmonary injury (i.e. capillary stress failure) evoked histamine release from airway inflammatory/mast cells contributes to exercise-induced arterial hypoxemia (EIAH) and that pre-exercise inhalation of nedocromil sodium mitigated EIAH in human subjects 'Med. Sci. Sports Exercise 29, (1997) 10-16'. Because exercise-induced pulmonary hemorrhage due to capillary stress failure is routinely observed in racehorses, we examined whether nedocromil inhalation would similarly benefit EIAH and desaturation of hemoglobin in horses. Two sets of experiments, namely, placebo stud...
Allisonella histaminiformans gen. nov., sp. nov. A novel bacterium that produces histamine, utilizes histidine as its sole energy source, and could play a role in bovine and equine laminitis. When cattle and horses are fed large amounts of grain, histamine can accumulate in the gastrointestinal tract, and this accumulation can cause an acute inflammation of the hooves (laminitis). When ruminal fluid from dairy cattle fed grain supplements was serially diluted in anaerobic MRS medium containing histidine (50 mM), histamine was detected at dilutions as high as 10(-7). The histidine enrichments were then transferred successively in an anaerobic, carbonate-based medium (50 mM histidine) without glucose. The histamine producing bacteria could not be isolated from the rumens of cattle fe...
Expression of a 4-(hydroxy-3-nitro-phenyl) acetyl (NP) specific equi-murine IgE antibody that mediates histamine release in vitro and a type I skin reaction in vivo. Due to characteristic clinical signs, immunoglobulins of isotype E (IgE) are believed to be involved in several allergic diseases of the horse. To date, closer investigations have been hampered by the fact that neither purified equine IgE nor anti-equine IgE monoclonal antibodies were available for IgE isotype determination. As an approach to solve this problem, we constructed a stable cell line (EqE6) that expresses recombinant equi-murine IgE specific for 4-(hydroxy-3-nitro-phenyl) acetyl (NP). Biochemical analysis of the purified protein revealed a highly glycosilated IgE monomer of approxi...
Anti-inflammatory agent, dexamethasone, does not affect exercise-induced arterial hypoxemia in Thoroughbreds. In view of the suggestion that pulmonary injury-induced release of histamine and/or other chemical mediators from airway inflammatory and mast cells contribute to the exercise-induced arterial hypoxemia (EIAH) in human athletes, we examined the effects of pretreatment with a potent anti-inflammatory agent, dexamethasone, on EIAH and desaturation of hemoglobin in horses. Seven healthy, sound, exercise-trained Thoroughbreds were studied in the control (no medications) experiments, followed in 7 days by intravenous dexamethasone (0.11 mg.kg(-1).day(-1) for 3 consecutive days) studies. Blood-gas m...
Contractile response of horse deep dorsal penile vein to histamine. The present investigation was designed to evaluate the effect of histamine on isolated rings of horse deep dorsal penile vein. Under precontracted or basal conditions, histamine evoked an endothelium-independent contraction. Preincubation of the vein rings with the selective H1 receptor antagonist, mepyramine, shifted the concentration-response curve for histamine and to the H1 receptor agonist 2-pyridylethylamine to the right in a competitive manner. Pretreatment with cimetidine, a specific H2 receptor antagonist, did not modify the pEC50 and maximal contraction of the histamine response. Cim...
H1-receptor antagonist, tripelennamine, does not affect arterial hypoxemia in exercising Thoroughbreds. It has been suggested that pulmonary injury and inflammation-induced histamine release from airway mast cells may contribute to exercise-induced arterial hypoxemia (EIAH). Because stress failure of pulmonary capillaries and EIAH are routinely observed in exercising horses, we examined whether preexercise administration of an H1-receptor antagonist may mitigate EIAH. Two sets of experiments, placebo (saline) and antihistaminic (tripelennamine HCl at 1.10 mg/kg iv, 15 min preexercise) studies, were carried out on seven healthy, exercise-trained Thoroughbred horses in random order 7 days apart. A...
Flowmetric comparison of respiratory inductance plethysmography and pneumotachography in horses. Respiratory inductance plethysmographic (RIP) and pneumotachographic (Pn) flows were compared dynamically in horses with bronchoconstriction. On a breath-by-breath basis, RIP was normalized to inspiratory volume from Pn, and peak [peak of subtracted final exhalation waveform (SFE(max))] and selected area [integral of subtracted final waveform during first 25% of exhaled volume (SFE(int))] differences between RIP and Pn flows during early expiration were measured in three settings: 1) healthy horses (n = 8) undergoing histamine bronchoprovocation; 2) horses with naturally occurring lower airway...
Inflammatory mediators induce endothelium-dependent adherence of equine eosinophils to cultured endothelial cells. Accumulation of equine eosinophils at sites of parasite infestation or allergic inflammation depends upon their adherence to vascular endothelial cells and subsequent migration through the endothelium and extracellular matrix. This study has examined whether cytokines, which cause endothelial cell-dependent eosinophil adherence in other species, and histamine and substance P, which increase adherence of equine eosinophils to protein coated plastic, induce equine eosinophil adherence to cultured equine digital vein endothelial cell (EDVEC) monolayers. The EDVEC monolayers were stimulated with r...
