Evidence of purinergic neurotransmission in isolated, intact horse sweat glands

• Published in: Veterinary dermatology 2013-08, Vol.24 (4), p.398-e86
• Main Authors: Bovell, Douglas L., Riggs, Christopher M., Sidlow, Gordon, Troester, Suzanne, MacLaren, William, Yip, Wallace, Ko, Wing H.
• Format: Article
• Language: English
• Subjects: Animals; Calcium Signaling; Fura-2 - analogs & derivatives; Horses - physiology; Isoproterenol; Receptors, Adrenergic, beta-2 - physiology; Receptors, Purinergic - physiology; Staining and Labeling; Sweat Glands - physiology; Synaptic Transmission - physiology
• ISSN: 0959-4493; 1365-3164
• DOI: 10.1111/vde.12042

Background Fluid secretion by sweat glands in response to heat and exercise is underpinned by increases in intracellular calcium. In horses, this is primarily via β2‐adrenoceptors, but studies in equine sweat gland cell lines have indicated a possible role for purinergic agonists. Knowledge of equine sweating stimulus–secretion mechanisms in intact glands from healthy animals would allow future comparison to determine whether these mechanisms are affected in equine anhidrosis. Hypothesis/Objectives To determine whether purinergic agonists can induce changes in intracellular calcium in intact, freshly isolated equine sweat glands. Animals Eleven healthy thoroughbred horses from the Hong Kong Jockey Club were used in this study. Methods Freshly isolated equine sweat glands were loaded with the calcium‐sensitive fluorescent dye fura‐2 AM, and changes in intracellular calcium were recorded before, during and after stimulation by purinergic agonists. Results Purinergic agonists ATP and UTP generated significant increases in intracellular calcium. Conclusions and clinical importance The results show that it is possible to investigate stimulus–secretion coupling mechanisms by fluorescence imaging in equine sweat glands that have been isolated from fresh skin samples. Such isolated glands retain functional β2‐adrenoceptors and P2Y purinergic receptors that couple to a calcium‐signalling pathway. Using isolated, intact sweat glands therefore offers a very useful model for the further study of secretory processes in equine sweat glands, and using this experimental approach could facilitate a better understanding of how these mechanisms are affected in equine anhidrosis. Résumé Contexte La sécrétion des glandes sudoripares en réponse à la chaleur et à l'exercice nécessite une augmentation en calcium intracellulaire. Chez le cheval, ceci se fait principalement par les β2‐adrenocepteurs mais les études des lignées cellulaires des glandes sudoripares chez le cheval indiquent un rôle possible des agonistes purinergiques. La connaissance des mécanismes de stimulation de la sécrétion de la sudation chez le cheval par les glandes intactes d'animaux sains permettrait de déterminer dans le futur si ces mécanismes sont affectés dans l'anhidrose équine. Hypothèses/Objectifs Déterminer si les agonistes purinergiques peuvent induire des modifications du calcium intracellulaire de glandes sudoripares équines intactes fraichement isolées. Sujets Onze chevaux pur‐sang sains du Hong