Cell cycle--dependent expression of L- and T-type Ca2+ currents in rat aortic smooth muscle cells in primary culture
Kuga, T.; Kobayashi, S.; Hirakawa, Y.; Kanaide, H.; Takeshita, A.
Circulation Research 79(1): 14-19
1996
ISSN/ISBN: 0009-7330 PMID: 8925562 Document Number: 459958
The expression of L- and T-type Ca-2+ 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 Ca-2+ 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 Ca-2+ 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 G-0 (n = 130) and M (n = 75) phases, all cells showed only L-type Ca-2+ currents. The cells showing a T-type Ca-2+ current appeared in the G-1 phase (37%, n = 85) and increased in the S phase (90%, n = 21). For L-type Ca-2+ channels, the current density was significantly greater in the G-1 phase than in the G-0 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 Ca-2+ current did not differ in the four phases of the cell cycle. These findings thus indicate that the expression of L- and T-type Ca-2+ channels depends on the cell cycle, whereas the characteristics of L-type Ca-2+ channels do not differ between the phases of the cell cycle.