SR2-SENSITIVE, CYTOPLASMIC CA2+ STORE IN A CELL-LINE DERIVED FROM THEEQUINE SWEAT GLAND EPITHELIUM( CAN BECOME INCORPORATED INTO AN AGONIST)

We have explored the properties of a Ca2+-dependent cell-signalling pa thway that becomes active when cultured equine sweat gland cells are s timulated with ATP. The ATP-regulated, Ca2+-influx pathway allowed Sr2 + to enter the cytoplasm but permitted only a minimal influx of Ba2+. Experiments in which cells were repeatedly stimulated with ATP suggest ed that Sr2+, but not Ba2+, could become incorporated into the agonist -sensitive, cytoplasmic Ca2+ store. Further evidence for this was prov ided by experiments using ionomycin, a Ca2+ ionophore which has no aff inity for Sr2+.