Inactivation of voltage-dependent calcium current in an insulinoma cell line |
| |
Authors: | Carla Marchetti Carolina Amico Daniela Podestà Mauro Robello |
| |
Institution: | (1) Istituto di Cibernetica e Biofisica, Consiglio Nazionale delle Ricerche, Via Dodecanesco 33, I-16146 Genova, Italy;(2) University degli Studi di Genova, Via Dodecanesco 33, 1-16146 Genova, Italy |
| |
Abstract: | We have studied the mechanism of Ca current inactivation in the -cell line HIT-T15 by conventional and perforated patch recording techniques, using two pulse voltage protocols and a combination of current and tail current measurements. In 5 mM Ca, from a holding potential of - 80 mV, the maximum current showed a complex time course of inactivation: a relatively fast, double exponential inactivation ( h1 12 ms and h2 60 ms) and a very slowly inactivating component ( > 1 s). The faster component ( h1) was due to the voltage-dependent inactivation of a low-threshold-activated (LVA), T-type current, which deactivates more slowly ( 3–5 ms) than the other components ( 0.2–0.3 ms). The intermediate component ( h2) was due to the Ca-dependent inactivation of a portion of the high-threshold-activated (HVA) current. A saturating dose of the dihydropyridine (DHP) nifedipine (10 M) did not affect the LVA current, but inhibited by 68 ± 5% the transient, Ca-sensitive portion of the HVA current and by 33 ± 12% the long lasting component. We suggest that three components of the calcium current can be resolved in HIT cells and the main target of DHPs is a HVA current, which inactivates faster than the DHP-resistant HVA component and does so primarily through calcium influx.
Correspondence to: C. Marchetti |
| |
Keywords: | -cells" target="_blank">gif" alt="beta" align="MIDDLE" BORDER="0">-cells Perforated patch recording Ca-dependent inactivation Dihydropyridines |
本文献已被 SpringerLink 等数据库收录! |
|