Although the composition of this fluid has been well documented for some time ( 8, 40), the mechanisms underlying fluid formation surprisingly remain poorly understood.Īs a general principle, fluid formation is secondary to and driven by the active transport of ions across an epithelial layer. The fluid formed within the oviduct provides an essential and appropriate environment for gamete maturation, transport, fertilization, and early embryo development. In conclusion, these results provide strong evidence that purinergic activation of a calcium-dependent, apamin-sensitive potassium conductance is essential to promote chloride secretion and thus fluid formation in the oviduct. Measurements of intracellular calcium using Fura-2 spectrofluorescence imaging revealed the ability of ATP e to increase intracellular calcium in a phospholipase C-inositol 1,4,5-trisphosphate pathway-sensitive manner. The presence of small conductance family member KCNN3 was confirmed by RT-PCR and immunohistochemistry. However, pretreatment with the small conductance inhibitor apamin resulted in a 60% reduction in the response to ATP e. Charbydotoxin, (high conductance and intermediate conductance inhibitor), or paxilline, (high conductance inhibitor) did not significantly alter the ATP e response.
To further investigate the type of K + channel involved in the ATP response in the bovine oviduct, a number of specific Ca 2+-activated K + channel inhibitors were tested on the ATP-induced Δ I SC in intact monolayers. Basolateral K + current, isolated using nystatin-perforation technique, was rapidly activated by ATP e, and pretreatment of monolayers with thapsigargin or TPeA abolished this ATP-stimulated K + current. Similarly, ATP-stimulated chloride secretion was significantly attenuated by pretreatment with BaCl 2, tetraethylammonium (TEA), tolbutamide, and TPeA. Basal I SC in bovine oviduct epithelium comprises both chloride secretion and sodium absorption and was inhibited by treatment with basolateral K + channel inhibitors tetrapentlyammonium chloride (TPeA) or BaCl 2. This study explored the role of potassium channels in basolateral extracellular ATP (ATP e)-stimulated ion transport in bovine oviduct epithelium using the Ussing chamber short-circuit current ( I SC) technique. As in other epithelia, both secretory and absorptive pathways are likely to work in tandem to drive appropriate ionic movement to support fluid movement across the oviduct epithelium. The molecular mechanisms controlling fluid secretion within the oviduct have yet to be determined.
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