Metabolic alkalosis in the larval salamander,Ambystoma tigrinum: Partitioning regulatory responses between the skin and kidneys
✍ Scribed by Stiffler, Daniel F. ;Bachoura, Norma
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 696 KB
- Volume
- 258
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Abstract
Larval Ambystoma tigrinum were non‐occlusively cannulated in the truncus arteriosus for blood collection. One group was infused with a single dose of 1 ml of 200 mM NaHCO~3~ to induce a metabolic alkalosis. This increased pH from 7.79 to 8.22 after 5 minutes. Bicarbonate ion concentration increased from 16.3 mM to 48.6 mM during this time. After 2 h [HCO~3~^−^] was still elevated but pH had returned to control as the P~CO2~ became elevated. A series of infusions of 1 ml of 200 mM NaHCO~3~ at 40 minute intervals into a second group of animals produced a prolonged alkalosis that persisted 8 hours. During this period C1^−^ influx increased by 130%. There was a similar increase in C1^−^ efflux resulting in no change in net C1^−^ flux. There was no significant change in Na^+^ influx, however, Na^+^ efflux increased by almost 150%. Bicarbonate fluxes were measured directly in a third group of serially infused animals whose cloacae were cannulated to permit partitioning of renal and extra renal routes of HCO~3~^−^ excretion. There was a significant increase in total HCO~3~^−^ excretion during alkalosis and 95% of it was extrarenal. Although the kidneys can increase base excretion during metabolic alkalosis their capacity is limited with the great majority of base excretion occurring across the skin and/or gills.