P2Y receptors are involved in epithelial transport in various tissue types (1), including sweat gland secretion via an increase in chloride permeability and changes in intracellular calcium ([Ca2+]_i) (2). Epithelial cells from isolated sweat glands of normal horses increase [Ca2+]_i in response to purinergic agonists such as ATP and UTP (3). Anhidrosis, or inability to sweat, is a debilitating condition affecting humans and horses thought to be caused by a failure in the secretory process. The aim of this study was to compare the presence and responses of P2Y receptor subtypes in sweat gland epithelial cells obtained from anhidrotic horses with those from normal animals. Epithelial cell lines were obtained from horse skin samples of normal, intermediate- and late-anhidrotic racing thoroughbreds in Hong Kong with ethics and owner approval. Local anaesthetic Lignocaine was injected into the skin prior to biopsy. Cells were cultured using standard tissue culture techniques. Epithelial cell lysates were used for Western blotting using antibodies against P2Y₂, P2Y₄ and P2Y₆ receptors. Cells were examined for changes in [Ca2+]_i evoked by various purinergic agonists using calcium imaging techniques. Values presented as mean ratio units ± S.D. Statistical analyses were carried out using one-way ANOVA and Bonferroni multiple comparison test, where P<0.001 was considered significant. Western blot analysis showed bands for P2Y₂, P2Y₄ and P2Y₆ receptors in all cell types. Higher band density was observed in late-anhidrotic cells for P2Y₂ and P2Y₄ receptors than in either intermediate-anhidrotic or normal cells. ATP (100µM) and UTP (100µM) evoked significantly higher [Ca2+]_i increases in intermediate-and late- anhidrotic cells in comparison to normal cells (Table 1). Additionally, UTP elicited a significantly higher [Ca2+]_i response than ATP in intermediate- and late-anhidrotic cells, but not in normal cells (Table 1). ADP (100µM, n=18) and UDP (100µM, n=18) elicited no response from any cell type. The results indicate that there may be additional P2Y₂ and P2Y₄ receptors in anhidrosis, which could account for the increased [Ca2+]_i response to UTP, as both of these receptors are sensitive to UTP. P2Y₆ (UDP-sensitive) receptors were also found to be present in all cell types, but UDP failed to increase [Ca2+]_i, possibly demonstrating non-functional P2Y₆ receptors in these cells. These findings suggest a potential role for P2Y receptors in anhidrosis.