Topic:Adrenal
The adrenal glands in horses are small endocrine organs located near the kidneys, responsible for producing a variety of hormones essential for physiological regulation. These hormones include cortisol, adrenaline, and aldosterone, which are involved in stress response, metabolism, and electrolyte balance. The functioning of the adrenal glands is integral to the horse's ability to respond to stressors and maintain homeostasis. Research in equine endocrinology often focuses on understanding the regulation of adrenal hormones, their role in equine health, and the impact of disorders such as equine Cushing's disease and adrenal insufficiency. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, function, and clinical implications of adrenal gland activity in horses.
Response of the adrenal cortex to tetracosactrin (ACTH1-24) in the premature and full-term foal. The changes in plasma cortisol concentration in the immediate postnatal period were examined in 3 groups of newborn foals and the response of the adrenal cortex to exogenous ACTH1-24 (tetracosactrin) was tested in 2 of these groups. In full-term Thoroughbred and Pony foals a rise in plasma cortisol occurred between 0 and 30 min after birth, whereas no significant cortisol changes could be detected within 2 h of birth in the group of prematurely delivered foals. These differences in plasma cortisol between term and premature foals were accompanied by differences in blood pH and lymphocyte and n...
Effect of adrenergic neurotransmitters upon the ejaculatory process in the stallion. Successful empirical treatment of 17 out of 24 stallions, which had failed to ejaculate after normal penile erection, intromission and friction, by chemical blockage of beta-receptors and additional stimulation of alpha-receptors led us to investigate stallions with normal ejaculatory patterns. In an initial experiment one adult half-bred stallion was injected with 4.88 mg noradrenaline hydrochloride (treatment A), 10 mg bunitrolol (treatment B = beta-receptor blockage) and a combination of treatment A and B. Investigations of the same stallion on dated occasions without treatment served as co...
Sweating in the intact horse and isolated perfused horse skin. 1. In intact horses, heat-induced sweating occurred initially as pulses, then as a continuous, synchronously fluctuating discharge. 2. I.V. adrenaline (Adr) induced sweating immediately; isoprenaline (Isop) elicited sweating after a delay; and phenylephrine (PhE) had no sudorific effect. 3. In isolated perfused skin, PhE induced an immediate small sweat discharge, Isop a slower sustained output and Adr a biphasic discharge. alpha- and beta-adrenergic antagonists blocked the first and second phases, respectively, of Adr-induced sweating. 4. The observed sweating patterns are consistent with ind...
Development of the adrenal cortex in the fetal foal: an ultrastructural study. The adrenal cortex from twelve fetal foals (gestational ages from 61 to 300 days) was examined by light and electron microscopy. Adrenal glands from three newborn foals were also examined by light microscopy. Between 61 and 100 days of gestation the adrenal cortex became organised into two distinct regions, the zona glomerulosa and zona fasciculata, which grew steadily in thickness until the 300th day. Between 300 days and birth there was a dramatic increase in the width of the zona fasciculata. From 200 days a narrow band of compact cells marked the cortico-medullary border. Though these cell...
[Practolol test for adrenergic beta receptor blockade in veterinary electrocardiographic diagnosis]. The receptor theory of the action of catecholamines as well as the synthesis and production of beta-adrenolytics gave new perspectives for the treatment of circulatory diseases and enabled to use the beta-adrenergic blockade in electrocardiographic diagnosis. The aim of this work was to study whether it is possible to modify the oral method of administration used in human beings, into intravenous one, and what an information could be obtained as to actual heart condition after practolol injection. The results can be summarized as follows:--Practolol-Polfa injected intravenously in amounts of 3...
Uptake of nucleotides and catecholamines by chromaffin granules from pig and horse adrenal medulla. The uptake of nucleotides and catecholamines into chromaffin granules from adrenals of pigs and horses is similar to that previously seen in bovine chromaffin granules. The rate of [3H]ATP uptake at 2 mM-ATP concentration was 0.42 +/- 0.06 and 0.15 +/- 0.02 nmol/mg protein/min for pig and horse granules, respectively. The apparent Km's were 1.37 mM for pig granules, 0.89 mM for horse granules, and 1.2 mM for ox granules. The sensitivity of the uptake for nucleotides and catecholamine to specific inhibitors was found to be similar in granules from pig and ox, indicating that the same mechanisms...
Vascular anatomy and surgical technique for bilateral adrenalectomy in the equid. The vascular anatomy of the adrenal glands and a surgical technique for bilateral adrenalectomy in the equid are described. Bilateral adrenalectomy was performed in six ponies and one horse via bilateral transcostal retroperitoneal approaches through the 18th rib during a single anesthetic period. Complications included hemorrhage from the right side only and pneumothorax which usually occurred on the right side. One pony died as a result of the surgical technique. Maintenance of adrenal function was accomplished with desoxycorticosterone pivilate and prednisolone.
[Correlations between the indices of the state of the sympathetic-adrenal and of the hypophyseal-adrenal systems and the level of insulin in horses under various exposures]. The content of adrenaline, noradrenaline, ACTH, cortisol and insulin in the blood and excretion of catecholamines with urine were studied in horses after physical and emotional exposures. The highest degree of the sympathoadrenal system (SAS) and hypophysioadrenal system (HAS) activation followed by the insulin content decrease was observed after training. The known emotional exposure (the noise of hyppodrome) astivated both parts of SAS and HAS. The unknown emotional experience (electronic music) produced a strong adrenal medullar reaction. Analysis of the correlations showed that the initial...
Electroacupuncture elevates blood cortisol levels in naive horses; sham treatment has no effect. It was hypothesized that electroacupuncture releases beta-endorphin and ACTH from the pituitary. Since ACTH induces the release of cortisol from the adrenal glands, blood cortisol level should be enhanced by electroacupuncture. The present result shows that the blood cortisol levels of horses are significantly increased after 30 min of electroacupuncture treatment while the sham treatment (control) shows an insignificant effect.
Metabolic and physiological effects of adrenoceptor agonists and antagonists in the horse. In the horse the effect of the adrenergenic agonists adrenaline, phenylephrine and salbutamol on haematocrit, plasma free fatty acid, glycerol and lactate levels were investigated. Effects on heart rate, sweating and muscle tremor were also studied. The effects of administration of the adrenoceptor antagonists propranolol, metoprolol, H35/25 and acepromazine on adrenaline-induced changes were examined. The results obtained with these agonists and antagonists suggest that the lipolysis and hyperglycaemia are mediated via beta-adrenoceptors. It appears that both beta1 and beta2 subtypes are invo...
Adrenal-testis interaction in the stallion. The authors describe the short and long term effects of synthetic adrenocorticotrophin and of cortisol on peripheral plasma testosterone concentrations in 2 stallions. A single injection of either hormone temporarily raised plasma testosterone concentrations but repeated injection (twice daily for 5 days) depressed plasma testosterone concentrations. Cessation of treatment was followed by a rise in plasma testosterone to concentrations higher than those in the pretreatment period. These findings are briefly discussed.
The actions of the beta-adrenoceptor blocking agents propranolol and metoprolol in the maximally exercised horse. The effects of two beta-adrenoceptor antagonists, propranolol (0.2 mg/kg) and metoprolol (0.2 mg/kg) on some physiological and metabolic changes produced by maximal exercise in the horse were investigated. Both drugs reduced the elevation in heart rate seen immediately following exercise and reduced performance as was seen by the increased time taken to perform each gallop. The rise in plasma glucose, glycerol and lactate, and the fall in blood pH seen following exercise were attenuated by both drugs. However, a greater increase in plasma free fatty acids occurred. Exercise produced a nine- to...
A light and electron microscopic study of a normal adrenal medulla and a pheochromocytoma from a horse. The outer medullary (juxtacortical) zone of a normal equine adrenal gland had columnar chromaffin-positive cells arranged with their long axes perpendicular to fine vascular channels. The deeper medullary regions were composed of smaller irregularly round to polygonal chromaffin positive cells in small packets. Both cell types contained two types of membrane-bound cytoplasmic secretory granules. Osmiophilic granules with a homogeneous core, crenated membrane and narrow submembranous halo predominated in the columnar juxtacortical cells. The rounder, central medullary cells contained predominan...
Adrenal gland function in the horse: effects of cosyntropin (synthetic) and corticotropin (natural) stimulation. The plasma concentration of hydrocortisone was determined in mares given either cosyntropin (100 IU, given IV) or corticotropin (200 IU, given IM). Plasma hydrocortisone concentrations of the mares treated with cosyntropin increased by 46%, 57% and 80% at 30, 60, and 120 minutes, respectively, when compared with base-line values; these values returned to base line at 240 minutes. In mares treated with corticotropin, mean plasma hydrocortisone concentrations increased by 42%, 143%, 101% and 155% at 30, 60, 120, and 240 minutes, respectively, when compared with base-line values. Differences in t...
A case of pituitary adrenocorticotropin-dependent Cushing’s syndrome in the horse. In the horse, a syndrome of hirsutism, hyperglycemia, glucosuria, polydipsia, polyuria, polyphagia, and progressive debilitation has been recognized. Most often the syndrome has been associated with adenomas of the pars intermedia of the pituitary and bilateral adrenal hyperplasia or nodular hyperplasia involving primarily the zona fasciculata. Previously, the syndrome has been ascribed to compression of the hypothalamus by an expanding but functionally inactive pituitary neoplasm. In the present case, with RIA determination of plasma ACTH concentrations, the syndrome was ascribed to pituitary...
Histological development of the equine fetal adrenal gland. The horse fetal adrenal gland was shown to begin to increase in weight from about the end of the 4th month of pregnancy when the fetus has a crown-rump length of about 20 cm. Growth then proceeds steadily to term but, in contrast to the adult horse, the medulla remains thicker than the cortex throughout fetal life. The cortex also becomes established around 20 cm crown-rump length and at the same time the glomerular and fascicular zones become distinguishable. In contrast the reticular zone is not differentiated until around 50 cm crown-rump length. In the fetal adrenal cortex, the fascicular ...
Spasmolytic action of histamine in airway smooth muscle of horse. Histamine, 2-methylhistamine (a specific H1-agonist), 5-HT, PGF2alpha, SRS-A, bradykinin (BK) and carbachol contract bronchial and tracheal smooth muscles of the horse. Isoprenaline, PGE1, E2, dimaprit and 4-methylhistamine (last two = specific H2-agonists) relaxed airways which were partially contracted to carbachol. Mepyramine (a specific H1-antagonist) selectively antagonized contractions to histamine. In the presence of mepyramine, histamine caused relaxation of airways partially contracted to carbachol. Metiamide and burimamide (specific H2-antagonists) specifically antagonized or reverse...
Identification of the receptor involved in adrenaline mediated sweating in the horse. Using adrenergic agonists and antagonists this study has demonstrated that adrenaline induced sweating is mediated via beta2-adrenoreceptors in the horse.
Biochemical and physiological effects of catecholamine administration in the horse. Adrenaline was given intramuscularly to resting horses. It increased heart rate, sweating, blood levels of lactic dehydrogenase, aldolase, creatine kinase, glucose, lactate, free fatty acids and glycerol. Responses to isoprenaline, to noradenaline and to adrenaline after pretreatment with propranolol indicated that beta receptors were involved in stimulation of tachycardia, sweating, lipolysis and muscle glycogenolysis, and alpha receptors in stimulation of liver glycogenolysis and leakage of intracellular enzymes. The time course and relative magnitude of the effects on different enzymes was ...
Hemodynamics and myocardial function during acute hypoxia in the pony. Hemodynamics and myocardial contractility were evaluated in 6 unanesthetized ponies during hypocapnic and isocapnic hypoxia and during hypocapnic hypoxia after beta adrenergic blockade with propranolol. Hypocapnic hypoxia, with a mean arterial oxygen pressure (PaO2) of 41.9 mm of Hg, produced a decrease in stroke index and an increase in heart rate, with no change of cardiac index. A moderate increase in left ventricular contractility occurred during hypocapnic hypoxia. Beta adrenergic blockade abolished changes in nearly all indices of left ventricular contractility during hypocapnic hypoxia,...
Recurrent esophageal obstruction due to squamous cell carcinoma in a horse. Squamous cell carcinoma involving the pars esophagea of the stomach caused recurrent esophageal obstruction in an 11 year old Pinto gelding. The tumor encircled the esophagus and was attached to the diaphragm, spleen, aorta, left adrenal gland and kidney. Definitive diagnosis was provided by biopsy of the mass via standing left flank laparotomy.
The applied pharmacology of azaperone in ponies. The butyrophenone tranquilliser, azaperone, was administered intramuscularly to ponies in five series of experiments, using a dose level of 0-4 mg/kg once and 0-8 mg/kg four times. An excellent or good sedative effect was usually obtained with both dose levels, but the response was more consistent with the higher dose. The onset of sedation was apparent within 10 min of administration, the maximal effect usually occurring between 20 and 60 min while sedation was no longer apparent after 2 to 6 h. Body temperature was reduced in all animals for at least 2 h and respiratory rate was increased in...
Development of pituitary and adrenal glands in the fetal horse. The various cell types in the adult anterior pituitary may be distinguished at the ultrastructural level of the sizes of the secretory granules within the cytoplasm. In the fetal adenohypophysis, with the exception of prolactin-producing cells, all types may be identified after Day 100 of gestation. Morphological evidence suggests that they are producing and secreting trophic hormones. The three constituent layers of the adrenal cortex are also discernible by Day 100 of pregnancy. The cells of the zona glomerulosa have large numbers of darkly stained inclusions within the cytoplasm. The zona f...