Table 9.
Less negative Vh of fast ramps markedly decreases INS and IPS in P but not in VM cells
| Param | VM cells n 7 | VM cells | P cells n 4 | P cells |
|---|---|---|---|---|
| Vh (mV) | −80 ± 0 | −50 ± 0 | −82.5 ± 2.5 | −55.0 ± 2.8 |
| IK1 peak (pA) | 999 ± 223 | 92 ± 19* | 270 ± 57 | 53.0 ± 15.5* |
| IK1 peak (mV) | −47.7 ± 4.4 | −41.5 ± 2.8 | −60 ± 3.4 | −47.0 ± 2.8* |
| INS (pA) | −388 ± 75 | −246 ± 46 | −261 ± 91 | −10.5 ± 6.5 (2/4) * |
| INS peak (mV) | −9.3 ± 4.7 | −22.7 ± 3.4 | −26.3 ± 3.0 | −35.8 ± 6.3 (2/4) |
| INa1 (pA) | −7988 ± 1170 | −298 ± 87* | −9334 ± 665 | −123 ± 123 (1/4) * |
| ICa start (mV) | −7.5 ± 4.7 | −7.1 ± 5.8 | 0 ± 0 | 0 ± 0 |
| ICa (pA) | −184 ± 52 | −183 ± 77 | 0 ± 0 | 0 ± 0 |
| ICa peak (mV) | 15.5 ± 10.3 | 13.6 ± 5.4 | 0 ± 0 | 0 ± 0 |
| Ito start (mV) | 5.6 ± 7.8 | 14.2 ± 4.6 | −15.4 ± 12 | −6.8 ± 17.7 |
| Ito peak (pA) | 341 ± 87 | 542 ± 132 | 1586 ± 579 | 1789 ± 667 |
| Iramp peak−Ih (pA) | 842 ± 154 | 284 ± 98* | 1597 ± 565 | 1826 ± 677 |
| Irepol (pA) | 192 ± 53 | 511 ± 104* | 1420 ± 582 | 1831 ± 679 |
| Irepol peak (mV) | 8.6 ± 7.5 | −5.6 ± 5.2 | −31.1 ± 5.3 | −30.9 ± 9.2 |
| IPS start (mV) | 5.7 ± 8.0 | 4.4 ± 4.5 | −28.8 ± 6.8 | 0 ± 0* |
| IPS peak (pA) | 214 ± 61 | 218 ± 63 | 36.0 ± 20 (3/4) | 0 ± 0 |
| IPS peak (mV) | −39.2 ± 6.0 | −41 ± 5.0 | −50.5 ± 5.0 | 0 ± 0* |
| IPS−Ih (pA) | 820 ± 198 | −5.0 ± 15.2* | 213 ± 81 (3/4) | 24.6 ± 15* |
n, number of cells studied; IK1 peak (pA), amplitude of IK1 peak in pA, measured as the difference from Ih; IK1 peak (mV), voltage in mV at which IK1 peaked; INS (pA), current amplitude in pA during the negative slope region; INS, peak (mV), voltage in mV of INS peak; INa1 (pA), amplitude in pA of INa1; ICa start (mV), beginning of ICa component in mV determined as the departure of current trace from INS peak; ICa (pA), amplitude of ICa component in pA as the difference between its beginning and its peak; ICa peak (mV), voltage in mV at which ICa peaked; Ito, start (mV), voltage in mV at which the increasing outward current started at INS or ICa peaks; Ito peak (pA), amplitude of outward current in pA measured between its beginning and ramp peak; Iramp peak−Ih (pA), outward current at ramp peak measured as difference from Ih; Irepol (pA), amplitude in pA of the outward current between ramp peak and its smallest value prior to the beginning of IPS; Irepol peak (mV), voltage in mV at which the outward current was smallest prior to INS beginning; IPS start (mV), voltage in mV at which IPS began; IPS peak (pA), current in pA at IPS peak, measured as difference between its beginning and its peak; IPS peak (mV), voltage in mV at which PS region peaked; IPS peak−Ih (pA), current in pA measured as difference between IPS peak and Ih; Vh (mV), holding potential in mV; Param, parameters measured; VM cells, data from ventricular myocardial cells; P cells, data from Purkinje cells; *statistically significant difference between the data at the two Vh values either in VM or P cells.