Table 1.
Effects of low and high luminal calcium concentration, calcium chelator, Ca-ATPase inhibitor, and IP3 receptor antagonist on flow-induced changes in cell volume and torque in mouse proximal tubules
| Group | n | Vo, nl/min | L, mm | Volume, μm3 | ID, μm | OD, μm | T/Tr |
|---|---|---|---|---|---|---|---|
| Control (1.2 mM CaCl2) | 15 | 5.2 ± 0.4 | 0.82 ± 0.02 | 929.4 ± 14.7 | 11.17 ± 0.4 | 36.17 ± 0.3 | 1.00 ± 0.05 |
| 15 | 20.5 ± 0.6 | 0.82 ± 0.02 | 1,044.6 ± 41.5* | 17.29 ± 0.3 | 40.29 ± 0.7 | 1.44 ± 0.06*** | |
| 5 mM CaCl2 | 6 | 4.6 ± 0.6 | 0.92 ± 0.07 | 940.8 ± 19.7NS | 11.46 ± 0.5 | 36.46 ± 0.5 | 1.00 ± 0.09 |
| 6 | 22.7 ± 1.2 | 0.92 ± 0.07 | 890.1 ± 13.1†ns | 18.33 ± 0.4 | 38.33 ± 0.4 | 1.66 ± 0.04†*** | |
| 0 mM CaCl2+EGTA | 6 | 5.2 ± 0.4 | 1.07 ± 0.07 | 888.7 ± 7.3NS | 11.04 ± 0.5 | 35.42 ± 0.3 | 1.00 ± 0.08 |
| 6 | 21.3 ± 0.6 | 1.07 ± 0.07 | 861.8 ± 7.3 †* | 17.43 ± 0.2 | 37.43 ± 0.2 | 1.37 ± 0.02NS** | |
| BAPTA+0 mM CaCl2+EGTA | 6 | 5.3 ± 0.5 | 0.98 ± 0.04 | 949.0 ± 20.7NS | 11.67 ± 0.5 | 36.67 ± 0.5 | 1.00 ± 0.06 |
| 6 | 20.3 ± 0.8 | 0.98 ± 0.04 | 877.0 ± 8.3†** | 17.92 ± 0.3 | 37.92 ± 0.3 | 1.40 ± 0.04NS*** | |
| Thapsigargin | 6 | 5.9 ± 0.8 | 1.01 ± 0.07 | 925.7 ± 25.3NS | 11.67 ± 0.4 | 36.25 ± 0.6 | 1.00 ± 0.08 |
| 6 | 21.6 ± 1.3 | 1.01 ± 0.07 | 877.0 ± 8.3†ns | 17.92 ± 0.3 | 37.92 ± 0.3 | 1.40 ± 0.05NS** | |
| 2-APB | 7 | 5.1 ± 0.5 | 0.98 ± 0.05 | 939.7 ± 16.7NS | 11.43 ± 0.4 | 36.43 ± 0.4 | 1.00 ± 0.08 |
| 7 | 21.1 ± 1.6 | 0.98 ± 0.05 | 858.3 ± 13.4††** | 17.32 ± 0.4 | 37.32 ± 0.4 | 1.54 ± 0.07NS*** |
Values are means ± SE; n: no. of perfused tubules; Vo, original perfusion rate; L, tubular length; volume formula is π*(OD/2)2*1 − π*(ID/2)2*1; 1 indicates the length or height is 1 μm; ID, inner tubular diameter; OD, outer tubular diameter; T, total torque; Tr, torque measured at the perfusion rate of 5 nl/min. The cell-permeable calcium chelator BAPTA-AM (2 × 10−5 M), 10−7 M intracellular Ca-ATPase inhibitor thapsigargin, and 10−5 M inositol 1,4,5-trisphosphate (IP3) receptor antagonist 2-aminoethoxydiphenyl borate (2-APB) were added to the luminal perfusate, respectively. ns, Not significantly different from low flow rate 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 rate (†P < 0.05, ††P < 0.01, †††P < 0.001).