Abstract:
:We have studied the large increase in macroscopic potassium channel current caused by catecholamines in mammalian cardiac cells. An increase in macroscopic K current could result from either an increase in the single-channel current or by an increase in the number of channels that are open. Therefore, we have measured nonstationary potassium current fluctuations under voltage clamp conditions to determine whether norepinephrine increases the current through this channel. The single-channel current (at a potential of -30 mV in 4 mM external [K]) was estimated to be 3.7 pA and was not altered by concentrations of norepinephrine up to 2 microM. The spectral density of the current fluctuations were fitted well by a sum of 2 Lorentzians with corner frequencies that correspond with the measured time constants for deactivation of the macroscopic K current tails. We conclude that the increase in macroscopic K current caused by norepinephrine in these cells is not the result of an increase in single-channel conductance and therefore must involve an increase in the number of open K channels.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Bennett PB,Kass R,Begenisich Tdoi
10.1016/S0006-3495(89)82872-3subject
Has Abstractpub_date
1989-04-01 00:00:00pages
731-8issue
4eissn
0006-3495issn
1542-0086pii
S0006-3495(89)82872-3journal_volume
55pub_type
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