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KMID : 0578320110320050397
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Molecules and Cells
2011 Volume.32 No. 5 p.397 ~ p.404
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Ion Currents Induced by ATP and Angiotensin II in Cultured Follicular Cells of Xenopus laevis
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Marcelino Montiel-Herrera
Ana Maria Zaske
Jesus Garcia-Colunga
Ataulfo Martinez-Torres
Ricardo Miledi
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Abstract
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Xenopus laevis oocytes are commonly used to study the biophysical and pharmacological properties of foreign ion channels and receptors, but little is known about those endogenously expressed in their enveloping layer of follicular cells (FCs). Whole-cell recordings and the perforated patch-clamp technique in cultured FCs held at -60 mV revealed that ATP (20-250 ?M) generates inward currents of 465 ? 93 pA (mean ? standard error) in ?60% of the FCs studied, whereas outward currents of 317 ? 100 pA were found in ?5% of the cells. The net effect of ATP on the FCs was to activate both mono- and biphasic inward currents, with an associated increase in membrane chloride conductance. Two-microelectrode voltage-clamp recor-dings of nude oocytes held at -60 mV disclosed that ATP elicited biphasic inward currents, corresponding to the well-known Fin and Sin-like currents. ATP receptor antagonists like suramin, TNP-ATP, and RB2 did not inhibit any of these responses. On the other hand, when using whole-cell recordings, 1 μM Ang II yielded smooth inward currents of 157 ? 45 pA in ?16% of the FC held at -60 mV. The net Ang II response, mediated by the activation of the AT1 receptor, was a chloride current inhibited by 10 nM ZD7155. This study will help to better understand the roles of ATP and Ang II receptors in the physiology of X. laevis oocytes.
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KEYWORD
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chloride current, follicular cells, oocytes, transmitters, whole-cell recording0
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