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Glucocorticoids have a different action than aldosterone on target tissue
J Halevy1, E L Boulpaep, M E Budinger
1Department of Medicine, Yale School of Medicine, New Haven, Connecticut 06510.
The American Journal of Physiology
|January 1, 1988
Summary
Glucocorticoids influence rat colon electrical properties via a distinct pathway, not by binding to aldosterone receptors. This specific mechanism affects ion transport independently of aldosterone receptor activity.
Area of Science:
- Physiology
- Endocrinology
- Molecular Biology
Background:
- Glucocorticoids are known to affect electrolyte transport in the colon.
- The precise mechanism, specifically whether it involves aldosterone receptors, remains unclear.
Purpose of the Study:
- To investigate if glucocorticoid effects on rat distal colon electrical properties are receptor-specific or involve cross-binding to aldosterone receptors.
- To elucidate the independent action of glucocorticoids on colonic ion transport.
Main Methods:
- Utilized a synthetic glucocorticoid, RU 28362, with negligible aldosterone receptor binding.
- Measured transepithelial potential differences (VT), equivalent short-circuit current (ISC), and epithelial resistance (RT).
- Performed cell-impalement studies to assess membrane potential changes and tested effects of amiloride and spironolactone.
Main Results:
- RU 28362 significantly altered VT, ISC, and RT, similar but less potent than aldosterone.
- RU 28362 showed minimal effects on basolateral and apical membrane potentials compared to aldosterone and dexamethasone.
- Amiloride and spironolactone, which inhibit aldosterone effects, had little impact on RU 28362-induced changes.
Conclusions:
- Glucocorticoids exert a specific, aldosterone receptor-independent effect on the electrical properties of the rat distal colon.
- This suggests a distinct molecular mechanism for glucocorticoid action on colonic ion transport.