| Author/Editor | Kocmur-Bobanović, L | |
| Title | Napetostno odvisne kalcijeve prevodnosti hipofiznih celic | |
| Type | monografija | |
| Place | Ljubljana | |
| Publisher | Medicinska fakulteta | |
| Publication year | 1994 | |
| Volume | str. 70 | |
| Language | slo | |
| Abstract | The aim of our study was to determine the types of voltage-activated calcium channels in the plasma membrane of rat melanotrophs. These excitable cells secrete a number of peptides including alphaMSH and endorphin. The role of voltage-activated calcium channels is well accepted in the regulation of hormone secretion, although roles of multiple calcium channel types are not clear. It is still under discussion whether rat melanotrophs possess two or three types of voltage-activated calcium channels: one low (=-50 mV; LVA) and one or two high voltage-activated (=-20 mV; HVA) ones. In order to isolate currents through voltage-activated calcium channels we used "whole cell" patch-clamp technique. We found that the success of calcium current registration depended on external calcium concentration as well as on the chloride concentration mostly cytosolic. In an attempt to solve the question of the number of calcium channel types in rat melanotrophs, we employed a new approach, based on applying voltage ramps of different gradients. The application of voltage ramps of 300 ms in duration (voltage gradient of 0.5 V/s) resulted in a clear separation of two inward current components conesponding to low and high voltageactivated calcium current components, since they are activated at different voltages (low and high voltage-activated respectively). To determine pharmacological characteristics of both current types we tested their sensitivity to dihydropyridines, phenylalkylamines and benzothiazepines, known as specific L-type high voltage-activated calcium channel blockers. Previously i t has been reported that only high voltage-activated calcium channels are sensitive to dihydropyridines BAY K 8644 and nifedipine.(trunc.) | |
| Descriptors | PITUITARY GLAND CALCIUM CHANNELS CELL MEMBRANE MELANOPHORES PATCH-CLAMP TECHNIQUES ANIMALS, LABORATORY RATS CYTOSOL DIHYDROPYRIDINES BAY K 8644 NIFEDIPINE NICARDIPINE NITRENDIPINE VERAPAMIL DILTIAZEM CHLORIDES CALCIUM |