Effect of purinergic stimulation on intracellular calcium concentration and transepithelial potential difference in...

Epithelial cells were removed from bovine oviducts by enzyme digestion and either cultured on laminin-coated coverslips (for determination of [Ca2+]i) or on collagen filters (for determination of transepithelial potential difference [pd]). Cells on coverslips were loaded with Fura-2 to monitor [Ca2+]i. Application of extracellular ATP induced a transient increase in [Ca2+]i in a dose-dependent manner. This response was abolished by thapsigargin, indicating that the rise in [Ca2+]i was derived from intracellular stores. The order of potency of the nucleotide-induced rise in [Ca2+]i was uridine triphosphate (UTP)>ATP>ADP. Epithelial cells were grown on collagen filters, and when mounted in a modified Ussing chamber exhibited an electrical pd of 1.00 +/- 0.36 mV with the apical side negative with respect to the basal. Application of UTP, ATP, and ADP to the basal side induced transient increases in pd of 1.15 +/- 0.21, 0.77 +/- 0.16, and 0.26 +/- 0.06 mV, respectively. The order of potency of the nucleotides in eliciting transient increases in [Ca2+]i and pd suggests the presence of a P2u purinergic receptor in the bovine oviduct epithelium that could play a role in transepithelial ion movements and hence the control of oviductal fluid formation.