UTP-dependent Inhibition of Na+ Absorption Requires Activation of PKC in Endometrial Epithelial Cells

The objective of this study was to investigate the mechanism of uridine 5′-triphosphate (UTP)-dependent inhibition of Na+ absorption in porcine endometrial epithelial cells. Acute stimulation with UTP (5 μM) produced inhibition of sodium absorption and stimulation of chloride secretion. Experiments using basolateral membrane–permeabilized cell monolayers demonstrated a reduction in benzamil-sensitive Na+ conductance in the apical membrane after UTP stimulation. The UTP-dependent inhibition of sodium transport could be mimicked by PMA (1 μM). Several PKC inhibitors, including GF109203X and Gö6983 (both nonselective PKC inhibitors) and rottlerin (a PKCδ selective inhibitor), were shown to prevent the UTP-dependent decrease in benzamil-sensitive current. The PKCα-selective inhibitors, Gö6976 and PKC inhibitor 20–28, produced a partial inhibition of the UTP effect on benzamil-sensitive Isc. Inhibition of the benzamil-sensitive Isc by UTP was observed in the presence of BAPTA-AM (50 μM), confirming that activation of PKCs, and not increases in [Ca2+]i, were directly responsible for the inhibition of apical Na+ channels and transepithelial Na+ absorption

Lucretia Mott Speaks: The Essential Speeches And Sermons

Committed abolitionist, controversial Quaker minister, tireless pacifist, fiery crusader for women\u27s rights--Lucretia Mott was one of the great reformers in America history. Drawing on widely scattered archives, newspaper accounts, and other sources, Lucretia Mott Speaks unearths the essential speeches and remarks from Mott\u27s remarkable career. The editors have chosen selections representing important themes and events in her public life. Extensive annotations provide vibrant context and show Mott\u27s engagement with allies and opponents. The result is an authoritative resource, one that enriches our understanding of Mott\u27s views, rhetorical strategies, and still-powerful influence

Apical SK potassium channels and Ca2+-dependent anion secretion in endometrial epithelial cells

Apical uridine triphosphate (UTP) stimulation was shown to increase short circuit current (Isc) in immortalized porcine endometrial gland epithelial monolayers. Pretreatment with the bee venom toxin apamin enhanced this response. Voltage-clamp experiments using amphotericin B-permeablized monolayers revealed that the apamin-sensitive current increased immediately after UTP stimulation and was K+ dependent. The current–voltage relationship was slightly inwardly rectifying with a reversal potential of −52 ± 2 mV, and the PK/PNa ratio was 14, indicating high selectivity for K+. Concentration–response relationships for apamin and dequalinium had IC50 values of 0.5 nm and 1.8 μm, respectively, consistent with data previously reported for SK3 channels in excitable cells and hepatocytes. Treatment of monolayers with 50 μm BAPTA-AM completely blocked the effects of UTP on K+ channel activation, indicating that the apamin-sensitive current was also Ca2+ dependent. Moreover, channel activation was blocked by calmidazolium (IC50= 5 μm), suggesting a role for calmodulin in Ca2+-dependent regulation of channel activity. RT-PCR experiments demonstrated expression of mRNA for the SK1 and SK3 channels, but not SK2 channels. Treatment of monolayers with 20 nm oestradiol-17β produced a 2-fold increase in SK3 mRNA, a 2-fold decrease in SK1 mRNA, but no change in GAPDH mRNA expression. This result correlated with a 2.5-fold increase in apamin-sensitive K+ channel activity in the apical membrane. We speculate that SK channels provide a mechanism for rapidly sensing changes in intracellular Ca2+ near the apical membrane, evoking immediate hyperpolarization necessary for increasing the driving force for anion efflux following P2Y receptor activation