Usage Information
Citation Information: J Clin Invest. 1982;69(4):759-769. https://doi.org/10.1172/JCI110514.
Abstract
Isolated cortical thick ascending limbs of Henle's loop were perfused in order to directly evaluate magnesium transport in this segment. Transepithelial potential difference was altered by varying the NaCl concentration in perfusate and bath and adding 50 microM furosemide to the perfusate. Perfusion under standard conditions with isotonic solutions resulted in a mean transepithelial potential difference of +8.8 +/- 0.7 mV and net magnesium absorption at a rate of 0.32 +/- 0.06 pmol/mm per min. Perfusion with a hypotonic solution significantly increased potential difference and the net absorptive rate of magnesium, calcium, and potassium. Conversely, reversal of the polarity of the potential difference with low NaCl bath and luminal furosemide produced net secretion of magnesium, calcium, and potassium. Parathyroid hormone in a bath concentration of 1.0 U/ml increased magnesium absorption from 0.32 +/- 0.06 to 0.63 +/- 0.06 pmol/mm per min (P less than 0.001) and calcium from 0.52 +/- 0.08 to 0.97 +/- 0.08 pmol/mm per min (P less than 0.001). Dibutyryl cyclic AMP produced similar effects on both calcium and magnesium absorption. Increasing bath calcium concentration twofold significantly inhibited net calcium absorption from 0.79 +/- 0.27 to 0.16 +/- 0.02 pmol/mm per min but magnesium transport was unaffected. Increasing bath magnesium concentration twofold significantly inhibited net magnesium absorption from 0.56 +/- 0.14 to -0.09 +/- 0.13 pmol/mm per min but had no effect upon net calcium transport. Net absorption of magnesium was significantly increased with increased concentration in the perfusate but calcium transport was unchanged. Similarly, increasing perfusate calcium concentration produced an increase in net calcium transport but did not alter magnesium transport. These data indicate that this segment of the loop of Henle is an important site for magnesium transport. Transport is influenced by luminal and bath concentration and is stimulated by parathyroid hormone and cyclic AMP. The data do not provide support for the concept of an interactive process between calcium and magnesium, and suggest that the positive transepithelial voltage is an important driving force for net reabsorption of magnesium, as well as calcium and potassium in this segment.
Authors
G R Shareghi, Z S Agus
Usage data is cumulative from August 2024 through August 2025.
| Usage | JCI | PMC |
|---|---|---|
| Text version | 230 | 19 |
| 52 | 7 | |
| Scanned page | 505 | 10 |
| Citation downloads | 76 | 0 |
| Totals | 863 | 36 |
| Total Views | 899 | |
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.
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)