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Expression of a hypotonic swelling-activated Cl conductance during ontogeny of collecting duct epithelium
1Physiologisches Institut, Ludwig-Maximilians-Universität, 80336 Munich, Germany.
Insights
Ion channel activity in developing rat kidney cells shifts from constitutive to swelling-activated during development. This study investigates chloride channel expression changes in embryonic and postnatal collecting duct cells.
Area of Science:
- Physiology
- Molecular Biology
- Developmental Biology
Background:
- Ion channels are crucial for cellular function, including regulatory volume decrease.
- Understanding developmental changes in ion channel expression is vital for kidney development research.
Purpose of the Study:
- To investigate the developmental expression of ion channels involved in regulatory volume decrease in rat ureteric bud and cortical collecting duct cells.
- To characterize the properties and activation patterns of chloride (Cl) channels during kidney development.
Main Methods:
- Primary monolayer cell cultures of rat embryonic (E17) and perinatal (P1-6) ureteric bud, and postnatal (P9-14) cortical collecting duct cells were used.
- Whole-cell patch-clamp electrophysiology was employed to measure ion channel conductance.
- DIDS sensitivity and ion permselectivity (I, Cl, Br, gluconate) were assessed under isotonic and hypotonic conditions.
Main Results:
- Whole-cell conductance was highest in embryonic (E17) cells and decreased in perinatal (P1-6) and postnatal (P9-14) cells.
- A DIDS-sensitive Cl conductance decreased significantly with development.
- Hypotonic conditions activated a time-dependent, inactivating Cl conductance in P1-6 and P9-14 cells, but not in E17 cells.
Conclusions:
- Chloride channel expression in developing kidney collecting duct cells shifts from a constitutively active form in embryonic stages to a hypotonic swelling-activated form in later development.
- These developmental changes in ion channel activity are critical for establishing proper kidney function.
Abstract:
Developmental expression of ion channels possibly participating in regulatory volume decrease was studied in rat embryonic (day E17) and perinatal (days P1-6) ureteric bud and in postnatal (P9-14) cortical collecting duct cells in primary monolayer culture. In isotonic bath solution, whole cell conductance (in nS/10 pF) was highest in E17 (4.0 +/- 0.5, n = 31) compared with P1-6 (2.0 +/- 0.1, n = 16) and P9-14 (1.3 +/- 0.2, n = 12) due to a decreasing contribution of a DIDS-sensitive Cl conductance, from E17 (2.8 +/- 0. 7, n = 12) to P1-6 (0.53 +/- 0.07, n = 9) and P9-14 (0.05 +/- 0.1, n = 7). Cl conductance in E17 exhibited a permselectivity of I approximately Cl approximately Br >> gluconate, and it activated time dependently. Hypotonic bath solution induced a large increase of whole cell conductance in P1-6 and in P9-14 but not in E17 (by 20. 0 +/- 3.7, 21.5 +/- 5.5, and 4.9 +/- 1.7; n = 11, 12, and 25, respectively) due to the activation of a time-dependently inactivating Cl conductance with a permselectivity of I >/= Br > Cl >> gluconate. In conclusion, the expression of Cl channels, as studied in vitro, appears to shift from an apparently constitutively active embryonic to a hypotonic swelling-activated type during late embryonic development of the collecting duct.