Table 4.
Comparison of quantitative characteristics, ionic sensitivity and pharmacology of spikes and [Ca2+]i transients recorded from GH-related cell lines (GH3 or GH4C1 and GC)
| A. Spikes | ||
|---|---|---|
| Parameter | GH3/GH4C1 | GC10 |
| Amplitude (mV) | 47.6 1 | 44.9 ± 1.9 |
| Peak (mV) | −12.4 ± 3.2 1 | −10.1 ± 1.2 |
| Duration (ms) | 184 ± 44 1 | — |
| Half-width (ms) | — | 180 ± 21 |
| Threshold (mV) | −44.5 ± 0.9 1 | −41.6 ± 1.1 |
| Time to peak (ms) | — | 164.3 ± 7.2 |
| Upstroke (V s−1) | 1.55 ± 0.30 1 | — |
| AHP (mV) | −60.0 ± 1.5 1 | −55.0 ± 1.4 |
| Frequency (Hz) | — | 0.38 ± 0.05 |
| Interspike interval (ms) | 3509 ± 1147 1 | 3200 ± 500 |
| 0 Ca2+ | blockade 2 | blockade |
| Inorganic Ca2+ channel blockers | blockade 234 | blockade |
| Nifedipine | blockade 3 | blockade |
| 0 Na+ | no effect 46 | hyperpolarization |
| hyperpolarization 3 | — | |
| TTX | no effect 346 | no effect |
| B. [Ca2+]i transients | ||
|---|---|---|
| Parameter | GH3/GH4C1 | GC 10 |
| Basal level (nM) | 123 ± 41 7 | 173 ± 20 |
| Amplitude (nM) | 236 ± 31 7 | 374 ± 57 |
| Half-width (ms) | — | 1000 ± 200 |
| Time to peak (ms) | 240 ± 16 | 872.5 ± 64.6 |
| Frequency (Hz) | 0.3 8 | 0.27 ± 0.03 |
| 0 Ca2+ | blockade579 | blockade |
| Cadmium | blockade 9 | — |
| Nifedipine | decrease 7 | blockade |
| blockade 95 | — | |