Table 3.
Effects of low and high luminal calcium concentration, calcium chelator, Ca-ATPase inhibitor, and IP3 receptor antagonist on flow-induced changes in bicarbonate absorption under low and high perfusion rates in mouse proximal tubules
| 5 nl/min |
20 nl/min |
||||||
|---|---|---|---|---|---|---|---|
| Group | n | JHCO3a, pmol·min−1·mm−1 | n | JHCO3b, pmol·min−1·mm−1 | ΔJHCO3 (JHCO3b − JHCO3a) | ΔJHCO3/JHCO3a * 100 | (ΔJHCO3/JHCO3a)/(ΔT/Tr) |
| Control (1.2 mM CaCl2) | 15 | 66.5 ± 3.7 | 15 | 135.6 ± 3.7*** | 69.1 ± 5.3 | 103.9 ± 5.6 | 2.36 ± 0.13 |
| 5 mM CaCl2 | 6 | 43.8 ± 4.3†† | 6 | 74.2 ± 7.8**††† | 30.4 ± 8.9††† | 69.5 ± 17.8† | 1.05 ± 0.27††† |
| 0 mM CaCl2+ EGTA | 6 | 63.1 ± 2.9NS | 6 | 136.4 ± 1.9***NS | 73.2 ± 3.5NS | 116.0 ± 3.1NS | 3.13 ± 0.08††† |
| BAPTA +0 mM CaCl2+EGTA | 6 | 72.1 ± 6.4NS | 6 | 92.3 ± 8.2ns††† | 20.2 ± 10.5††† | 28.0 ± 11.4††† | 0.70 ± 0.29††† |
| Thapsigargin | 6 | 49.9 ± 8.7NS | 6 | 78.5 ± 5.1*††† | 28.6 ± 10.1††† | 57.4 ± 10.2††† | 1.44 ± 0.25††† |
| 2-APB | 7 | 68.0 ± 2.7NS | 7 | 81.4 ± 6.1ns††† | 13.4 ± 6.7††† | 19.7 ± 9.0††† | 0.36 ± 0.17††† |
Values are means ± SE; n, no. of perfused tubules; JHCO3, bicarbonate absorption; ΔJHCO3, the differences in JHCO3 between perfusion rate of 5 and 20 nl/min; ΔJHCO3/JHCO3a * 100, percent changes in bicarbonate reabsorption from low flow rate. ns, Not significantly different from low flow rates in the same group.
Significant difference from low flow rates in the same group (*P < 0.05, **P < 0.01, ***P < 0.001). NS, not significantly different compared with control at the similar flow rates.
Significant difference compared with control at the similar flow rates (†P < 0.05, ††P < 0.01, †††P < 0.001).