Cell cycle--dependent expression of L- and T-type Ca2+ currents in rat aortic smooth muscle cells in primary culture.
The expression of L- and T-type Ca2+ channels has been reported to change during various biological events, including cellular differentiation and proliferation. The present study aimed to examine whether or not the expression of L- and T-type Ca2+ channels depends on the cell cycle in rat aortic smooth muscle cells in primary culture. Both the phase of the cell cycle and the functional expression of Ca2+ channels were determined in the same single cell, using an immunocytochemical analysis of cell cycle-specific nuclear antigens and a whole-cell voltage-clamp method, respectively. In the G0 (n = 130) and M (n = 75) phases, all cells showed only L-type Ca2+ currents. The cells showing a T-type Ca2+ current appeared in the G1 phase (37%, n = 85) and increased in the S phase (90%, n = 21). For L-type Ca2+ channels, the current density was significantly greater in the G1 phase than in the G0 and M phases. However, either the voltage-dependent properties or the dose-response relationships of Bay K 8644- and second messenger-induced modulations of L-type Ca2+ current did not differ in the four phases of the cell cycle. These findings thus indicate that the expression of L- and T-type Ca2+ channels depends on the cell cycle, whereas the characteristics of L-type Ca2+ channels do not differ between the phases of the cell cycle.
Kuga
T
T
Research Institute of Angiocardiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Kobayashi
S
S
Hirakawa
Y
Y
Kanaide
H
H
Takeshita
A
A
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000502:physiology; D015220:Calcium Channels / Q000502:physiology*; D002453:Cell Cycle; D002478:Cells, Cultured; D004553:Electric Conductivity; D016193:G1 Phase; D008297:Male; D008938:Mitosis; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D051381:Rats; D017208:Rats, Wistar; D016192:Resting Phase, Cell Cycle; D013997:Time Factors
D015220:Calcium Channels