Evolution of FRET ratio and properties of Ca2+ release flux
| Conditions | R initial | R final | Peak flux | Amount | [Ca]SR initial | [Ca]SR final | n cells |
| mM s−1 | µM | µM | µM | ||||
| WT EGTA | 1.32 (0.03) | 1.04 (0.03) | 54.6 (9.7) | 1,926 (259) | 507 (99.0) | 179 (19.3) | 14 |
| WT BAPTA | 1.26 (0.04) | 1.07 (0.05) | 119 (11.8)a | 1,093 (65.9)a | 437 (54.1) | 201 (26.8) | 22 |
| All WT | 1.28 (0.03) | 1.06 (0.03) | 94.0 (9.6) | 1,416 (126) | 464 (50.2) | 207 (18.6) | 36 |
| Null EGTA | 1.25 (0.07) | 0.68 (0.04)b | 43.4 (6.7) | 1,189 (174)b | 448 (111) | 39 (9.99)a | 9 |
| Null BAPTA | 1.35 (0.04) | 0.74 (0.04) | 115 (15.3)a | 982 (78.8) | 604 (100) | 59 (8.30)a | 14 |
| All null cells | 1.32 (0.04) | 0.72 (0.03)b | 89.2 (12.4) | 1,061 (82.7)b | 547 (75.2) | 51 (8.46)a | 23 |
| Conditions | R initial | R final | Peak flux | Amount | [Ca]SR initial | [Ca]SR final | n cells |
| mM s−1 | µM | µM | µM | ||||
| WT EGTA | 1.32 (0.03) | 1.04 (0.03) | 54.6 (9.7) | 1,926 (259) | 507 (99.0) | 179 (19.3) | 14 |
| WT BAPTA | 1.26 (0.04) | 1.07 (0.05) | 119 (11.8)a | 1,093 (65.9)a | 437 (54.1) | 201 (26.8) | 22 |
| All WT | 1.28 (0.03) | 1.06 (0.03) | 94.0 (9.6) | 1,416 (126) | 464 (50.2) | 207 (18.6) | 36 |
| Null EGTA | 1.25 (0.07) | 0.68 (0.04)b | 43.4 (6.7) | 1,189 (174)b | 448 (111) | 39 (9.99)a | 9 |
| Null BAPTA | 1.35 (0.04) | 0.74 (0.04) | 115 (15.3)a | 982 (78.8) | 604 (100) | 59 (8.30)a | 14 |
| All null cells | 1.32 (0.04) | 0.72 (0.03)b | 89.2 (12.4) | 1,061 (82.7)b | 547 (75.2) | 51 (8.46)a | 23 |
Effects of long lasting depolarization are shown. The second column shows initial FRET ratio in resting cells. The third column shows steady value of ratio reached after a pulse to 30 mV, 0.4–0.5 s long in experiments with BAPTA or 1–1.5 s in experiments with EGTA. Note that R initial is approximately the same for different preparations, but the extent of decay (depletion) is much greater in Casq-null cells. The fourth and fifth columns show peak Ca2+ release flux and amount released after the maximal long-lasting pulse. Note significantly greater peak flux in BAPTA but no difference in peak flux values between WT and nulls. Amount released is decreased in the null cells by about 30%. The sixth and seventh columns show initial and final values of [Ca2+]SR, calculated from corresponding R values. SEM values are shown in parentheses.
Values in BAPTA are significantly different from those in EGTA.
Values in null are significantly different from those in WT.