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Effects of tetracyclines on aldosterone- and insulin-mediated Na+ transport in the toad urinary bladder
Abstract:
The effect of oxytetracycline and demethylchlortetracycline on aldosterone- and insulin-mediated Na+ transport (short-circuit current) were examined in toad urinary bladders mounted in modified Ussing chambers. Oxytetracycline had little or no effect on either basal or aldosterone-mediated Na+ transport. In contrast, demethylchlortetracycline markedly inhibited both basal and aldosterone-mediated Na+ transport. Furthermore, demethylchlortetracycline inhibited the aldosterone response significantly out of proportion to its effects on basal Na+ transport. Neither of the drugs had an effect on insulin-mediated Na+ transport. Consequently, the natriuresis observed in certain patients treated with demethylchlortetracyline may be related to drug-induced renal resistance to the effects of aldosterone.
Insights
Demethylchlortetracycline inhibits sodium transport in toad bladders, potentially causing kidney resistance to aldosterone. Oxytetracycline showed no significant effect on aldosterone- or insulin-mediated sodium transport.
Area of Science:
- Nephrology
- Pharmacology
- Cell Physiology
Background:
- Aldosterone is a key hormone regulating sodium (Na+) reabsorption in the kidneys.
- Tetracycline antibiotics, including demethylchlortetracycline, are known to cause side effects such as electrolyte imbalances.
- The precise mechanisms by which certain tetracyclines affect renal tubular function remain incompletely understood.
Purpose of the Study:
- To investigate the effects of oxytetracycline and demethylchlortetracycline on sodium transport pathways.
- To determine the impact of these antibiotics on aldosterone- and insulin-mediated sodium transport.
- To elucidate the potential link between demethylchlortetracycline and aldosterone resistance in the renal system.
Main Methods:
- Utilized toad urinary bladders as an in vitro model system.
- Employed modified Ussing chambers to measure short-circuit current, representing Na+ transport.
- Administered oxytetracycline and demethylchlortetracycline to assess their effects on basal, aldosterone-stimulated, and insulin-stimulated Na+ transport.
Main Results:
- Oxytetracycline exhibited minimal to no impact on basal or aldosterone-mediated Na+ transport.
- Demethylchlortetracycline significantly inhibited both basal and aldosterone-mediated Na+ transport.
- The inhibitory effect of demethylchlortetracycline on aldosterone response was disproportionately greater than its effect on basal Na+ transport.
- Neither antibiotic affected insulin-mediated Na+ transport.
Conclusions:
- Demethylchlortetracycline interferes with renal sodium transport mechanisms.
- The drug may induce resistance to the effects of aldosterone in the kidneys.
- This mechanism could explain the natriuresis observed in patients treated with demethylchlortetracycline.