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Inner medullary collecting duct function during rebound alkalemia.
The American Journal of Physiology
|April 1, 1987
Summary
Rebound metabolic alkalemia (RMA) in rats shows continued proton secretion in the inner medullary collecting duct (IMCD), despite systemic alkalemia. This suggests factors beyond blood pH regulate IMCD function during RMA.
Area of Science:
- Nephrology
- Renal Physiology
- Acid-Base Balance
Background:
- Rats fed ammonium chloride (NH4Cl) develop metabolic acidosis.
- Discontinuation of NH4Cl leads to rebound metabolic alkalemia (RMA).
- The inner medullary collecting duct (IMCD) plays a role in acid-base regulation.
Purpose of the Study:
- To investigate the function of the IMCD during RMA.
- To determine if proton secretion in the IMCD is altered during systemic alkalemia.
Main Methods:
- Rats were induced into RMA by NH4Cl feeding followed by water.
- Arterial blood gases and pH were measured.
- IMCD fluid was collected using microcatheterization from deep and tip samples.
- Measurements included pH, PCO2, bicarbonate, titratable acid, and ammonium delivery.
Main Results:
- IMCD fluid pH decreased and PCO2 increased from deep to tip samples.
- Bicarbonate delivery decreased along the IMCD.
- Titratable acid and ammonium delivery increased along the IMCD.
- Calculated net acid excretion increased from deep to tip samples.
Conclusions:
- Proton secretion continues along the IMCD during RMA, despite systemic alkalemia.
- Factors other than systemic acid-base status appear to regulate IMCD proton secretion.
- IMCD function is maintained even when the body is in an alkalemic state.