CaV 3.1 and CaV 3.3 account for T-type Ca2+ current in GH3 cells.
T-type Ca2+ channels are important for cell signaling by a variety of cells. We report here the electrophysiological and molecular characteristics of the whole-cell Ca2+ current in GH3 clonal pituitary cells. The current inactivation at 0 mV was described by a single exponential function with a time constant of 18.32 +/- 1.87 ms (N = 16). The I-V relationship measured with Ca2+ as a charge carrier was shifted to the left when we applied a conditioning pre-pulse of up to -120 mV, indicating that a low voltage-activated current may be present in GH3 cells. Transient currents were first activated at -50 mV and peaked around -20 mV. The half-maximal voltage activation and the slope factors for the two conditions are -35.02 +/- 2.4 and 6.7 +/- 0.3 mV (pre-pulse of -120 mV, N = 15), and -27.0 +/- 0.97 and 7.5 +/- 0.7 mV (pre-pulse of -40 mV, N = 9). The 8-mV shift in the activation mid-point was statistically significant (P < 0.05). The tail currents decayed bi-exponentially suggesting two different T-type Ca2+ channel populations. RT-PCR revealed the presence of alpha1G (CaV3.1) and alpha1I (CaV3.3) T-type Ca2+ channel mRNA transcripts.
Mudado
M A
MA
Laboratório de Membranas Excitáveis, Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
Rodrigues
A L
AL
Prado
V F
VF
Beirão
P S L
PS
Cruz
J S
JS
D020747:Calcium Channels, T-Type / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D002999:Clone Cells; D004594:Electrophysiology; D006801:Humans; D010902:Pituitary Gland / Q000166:cytology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D020747:Calcium Channels, T-Type