Modulation of Ca2 influx in the ovine somatotroph by growth hormone- releasing factor

Abstract

Voltage-gated Ca2+ currents were recorded using the nystatin-perforated whole cell recording configuration on the ovine somatotrophs. With the use of Ca2+ -tetraethylammonium chloride bath solution and Cs+ electrode solution, two types of Ca2+ currents were obtained with a predominant long- lasting (L) current blocked by nifedipine. A transient (T) current was isolated in the presence of nifedipine (3 μM) and was not blocked by ω- conotoxin (5 μM), but diminished to 47 ± 5% of control by Ni2+ (0.3 mM) or to 52 ± 10% of control by amiloride (0.5 mM). The nifedipine-blockable L- type current was not affected by ω-conotoxin (5 μM); it was, however, attenuated to 80 ± 4% of control by Ni2+ (0.3 ..