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.
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