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Isolated MTAL cells produce an inhibitor of ouabain-sensitive oxygen consumption
L G Cantley1, R Fuhro, P Silva
1Department of Medicine, Beth Israel Hospital, Boston, Massachusetts 02215.
Abstract:
Dispersed medullary thick ascending limb (MTAL) cells of the rabbit kidney produce an inhibitor of transport-related oxygen consumption when incubated at 37 degrees C. Appearance of this inhibitor is enhanced by incubation with arachidonic acid. Its appearance can be prevented by either 10(-6) M nordihydroguaiaretic acid or 10(-4) M indomethacin, but not by 10(-6) M indomethacin. These results suggest that the transport inhibitor is an eicosanoid produced by a pathway other than that catalyzed by cyclooxygenase. It inhibits ouabain-sensitive respiration in intact cells treated with amphotericin, suggesting direct inhibition of the Na(+)-K(+)-ATPase.
Insights
Rabbit kidney cells produce an inhibitor of oxygen consumption, likely an eicosanoid, that directly affects the Na-K-ATPase. This process is enhanced by arachidonic acid and blocked by specific inhibitors, suggesting a non-cyclooxygenase pathway.
Area of Science:
- Nephrology
- Cell Physiology
- Biochemistry
Background:
- Medullary thick ascending limb (MTAL) cells are crucial for kidney function.
- Transport processes in MTAL cells are energy-dependent, relying on oxygen consumption.
- The precise mechanisms regulating MTAL cell energy metabolism are not fully understood.
Purpose of the Study:
- To investigate the production of an inhibitor of transport-related oxygen consumption by rabbit kidney MTAL cells.
- To elucidate the biochemical pathway and nature of this inhibitor.
- To determine the cellular target of the inhibitor.
Main Methods:
- Incubation of dispersed rabbit kidney MTAL cells at 37°C.
- Assessment of oxygen consumption.
- Treatment with arachidonic acid, nordihydroguaiaretic acid (NDGA), and indomethacin.
- Cell treatment with amphotericin to assess ouabain-sensitive respiration.
Main Results:
- MTAL cells produced an inhibitor of oxygen consumption when incubated at 37°C.
- Arachidonic acid enhanced inhibitor appearance.
- Nordihydroguaiaretic acid (10⁻⁶ M) and indomethacin (10⁻⁴ M) prevented inhibitor appearance, but 10⁻⁶ M indomethacin did not.
- The inhibitor affected ouabain-sensitive respiration, indicating direct inhibition of Na-K-ATPase.
Conclusions:
- The transport inhibitor is likely an eicosanoid.
- The eicosanoid is produced via a pathway independent of cyclooxygenase.
- The inhibitor directly targets the Na-K-ATPase in MTAL cells, impacting kidney transport functions.