Small conductance potassium channels drive ATP-activated chloride secretion in the oviduct

Abstract

Keating N, Quinlan LR. Small conductance potassium channels drive ATP-activated chloride secretion in the oviduct. Am J Physiol Cell Physiol 302: C100 -C109, 2012. First published September 14, 2011; doi:10.1152/ajpcell.00503.2010.-The molecular mechanisms controlling fluid secretion within the oviduct have yet to be determined. 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. 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. Basal I SC in bovine oviduct epithelium comprises both chloride secretion and sodium absorption and was inhibited by treatment with basolateral K ϩ channel inhibitors tetrapentlyammonium chloride (TPeA) or BaCl 2. Similarly, ATP-stimulated chloride secretion was significantly attenuated by pretreatment with BaCl 2, tetraethylammonium (TEA), tolbutamide, and TPeA. Basolateral K ϩ 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 ϩ current. To further investigate the type of K ϩ channel involved in the ATP response in the bovine oviduct, a number of specific Ca 2ϩ -activated K ϩ channel inhibitors were tested on the ATP-induced ⌬I SC in intact monolayers. Charbydotoxin, (high conductance and intermediate conductance inhibitor), or paxilline, (high conductance inhibitor) did not significantly alter the ATP e response. However, pretreatment with the small conductance inhibitor apamin resulted in a 60% reduction in the response to ATP e. The presence of small conductance family member KCNN3 was confirmed by RT-PCR and immunohistochemistry. 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. In conclusion, these results provide strong evidence that purinergic activation of a calciumdependent, apamin-sensitive potassium conductance is essential to promote chloride secretion and thus fluid formation in the oviduct. oviduct epithelium; apamin; fertilization THE FLUID formed within the oviduct provides an essential and appropriate environment for gamete maturation, transport, fertilization, and early embryo development. Although the composition of this fluid has been well documented for some time (8,40), the mechanisms underlying fluid formation surprisingly remain poorly understood.As a general principle, fluid formation is secondary to and driven by the active transport of ions across an epithelial layer.

Purinergic signalling in the reproductive system in health and disease

“…Purinergic signalling via P2Y 2 receptors also constitutes a key mechanism for regulating chloride secretion and thus fluid formation in the bovine oviduct [193]. In a later paper, they claimed that purinergic activation of a calcium-dependent, apaminsensitive potassium conductance was essential to promote chloride secretion [194].…”

Validation of markers with non-additive effects on milk yield and fertility in Holstein and Jersey cows

“…Both of the top SNPs in Holstein (rs134910746) and Jersey (rs29020504) populations on the interval extended from 15.8 to 16.0 Mbp on BTA 3 were found to be inside intronic regions of potassium intermediate/small conductance calcium-activated channel, subfamily N, member 3 ( KCNN3 ) gene. KCCN3 plays a key role in fluid secretion within the bovine oviduct which is essential to provide an appropriate environment for gamete maturation, transport, fertilization and early embryo development [ 45 ]. It has also been shown that KCNN3 is differentially expressed between oocytes and granulosa cells (GCs) during development of the sheep ovarian follicle [ 46 ].…”

Purinergic Signalling in the Reproductive System

“…The effect was mediated by activation of P2Y 2 or possibly P2Y 4 receptors (Cox and Leese, 1994;Villalon et al, 1995) located on the basal surface of the cells; it involved a rapid increase in Ca 2+ i due to Ca 2+ mobilization (Cox and Leese, 1994;Villalon et al, 1995;Dickens et al, 1996;Anon. ;Squires et al, 1995;Tiemann et al, 1996) and activation of Ca 2+ -dependent, apaminsensitive K + conductance (Keating and Quinlan, 2012). This mode of purinergic regulation of fluid and solutes secretion is common in secretory epithelia (Novak, 2008;Burnstock, 2014b).…”