The mode of action of aldosterone on the energetics of H+ transport in the turtle bladder was examined with the rate of glucose oxidation as an index of the metabolic activity of the epithelium (we show that H+ transport is not coupled to fatty acid oxidation). Within 6 h of addition of aldosterone H+, transport increased; so did glucose oxidation. The amount of H+ transport per mole of 14CO2 produced from glucose oxidation was 15.6 eq-mol-1 in the control hemi-bladder, while in the aldosterone-treated bladder it was 13.6, delta = 2.0+/-4.0 (n = 6). However, in bladders exposed to aldosterone for 20 h, the relation of transport to glucose oxidation was significantly altered: control 10.8, aldosterone 16.4, delta = 4.5+/-2.5, P less than 0.02, n = 7. The slope of H+ transport on the applied electrochemical gradient was steeper during both short- and long-term incubations. However, the maximum gradient necessary to nullify the net rate of secretion was unaltered in both experiments. Evidence is presented that aldosterone does not alter the passive backflux into the cell. In five additional experiments where aldosterone produced no significant stimulation of H+ transport, no change was noted in any of the metabolic or transport characteristics measured, suggesting that the alterations discussed above are dependent on the stimulation of H+ transport by the hormone. These results, along with some thermodynamic considerations, suggest that the effect of aldosterone is primarily exerted on the transport process rather than on metabolism. Further, it appears that prolonged stimulation of transport work leads to secondary alterations in the metabolic pathways reminiscent of the changes that occur in skeletal muscles of athletes undergoing physical conditioning.
Q Al-Awqati
Usage data is cumulative from April 2023 through April 2024.
Usage | JCI | PMC |
---|---|---|
Text version | 128 | 0 |
79 | 19 | |
Scanned page | 113 | 0 |
Citation downloads | 13 | 0 |
Totals | 333 | 19 |
Total Views | 352 |
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.