ISSN:
1432-1424
Keywords:
inwardly and outwardly rectifying K+ currents
;
BK channels
;
TEA
;
Ba2+
;
Cs+
;
sheep parotid
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary We have used whole-cell patch-clamp techniques to examine the sensitivities of the inwardly and the outwardly rectifying K+ currents in sheep parotid cells to K+ channel blockers. Extracellular tetraethylammonium (ID50 ≈ 200 μmol/liter), quinine (ID50 ≈ 100 μmol/liter), verapamil (ID50 ≈ 30 μmol/liter) and charybdotoxin (ID50 〈 0.1 μmol/liter) reduced the outwardly rectifying current but had no effect on the inwardly rectifying current. Quinidine inhibited the outwardly rectifying current (ID50 ≈ 200 μmol/liter) and, at a concentration of 1 mmol/liter, reduced the inwardly rectifying current by 35%. Extracellular Ba2+ inhibited both the inwardly and outwardly rectifying K+ currents but the inwardly rectifying K+ current was more sensitive to it (ID50 ≈ 1 μmol/liter) than was the outwardly rectifying K+ current (ID50 ≈ 2 mmol/liter). Extracellular Cs+ reduced the inwardly rectifying K+ current (ID50 ≈ 100 μmol/liter) without affecting the outwardly rectifying current; 4-aminopyridine (1 or 10 mmol/liter), lidocaine (0.1 or 1 mmol/liter) and flecainide (0.01 or 0.1 mmol/liter) affected neither current. In excised outsideout patches, the addition to the bath of quinine (100 μmol/liter), quinidine (100 μmol/liter), verapamil (100 μmol/liter) or charybdotoxin (100 nmol/liter) inhibited Ca2+- and voltage-sensitive 250 pS K+ channels (BK channels), but 4-aminopyridine (1 mmol/ liter) and lidocaine (0.1 mmol/liter) did not. The pattern of blocker sensitivities is thus consistent with the hypothesis that BK channels are responsible for the outwardly rectifying whole-cell current seen in resting sheep parotid cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00231875
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