Evidence of purinergic neurotransmission in isolated, intact horse sweat glands.

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.