|Budget Amount *help
¥1,700,000 (Direct Cost : ¥1,700,000)
Fiscal Year 1998 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1997 : ¥1,200,000 (Direct Cost : ¥1,200,000)
(1) Formation of single channel subconductance is one of the unique characteristics of the L-type Ca^2^+ channel. The alpha, subunit exhibits a primary function of the channel, it remains uncertain whether alpha subunit alone is able to produce subconductance.
(2) We tested this by studying single channel currents of cloned cardiac alpha subunit expressed in Chinese hamster fibroblast (CHW) cells, with/without coexpression of cardiac beta subunit.
(3) The alpha, subunit exhibited four distinct levels of conductance (22.7, 14.3, 6.2 and 3.2 pS).
(4) Coexpression of beta subunit significantly increased the number of openings in all four levels of conductance without changing the conductance values.
(5) In whole-cell clamp study, both a1 channel and alpha, /beta channel yielded currents that peaked at -10 ms after voltage step. With coexpression of the beta subunit, the maximum peak currents were increased by -5 times and the fractional conductance curve were shifted to the negative potential by -10 mY.
(6) In single channel study, with coexpression of the beta subunit,
(1) The mean available time for channel openings was incresed,
(2) The burst duration was marginally increased,
(3) The mean first latency was shortened,
(4) The mean open time was increased, yielding a second open state,
(5) The mean closed times were unchanged.