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Impaired cyclic AMP generation in outer medullary tubules of gentamicin-treated rats
D Kidwell1, S Subramaniam, C Ott
1Department of Physiology and Biophysics, University of Kentucky College of Medicine, Lexington 40536-0084.
Abstract:
We have examined the effects of chronic gentamicin treatment on arginine8-vasopressin (AVP)-dependent cyclic AMP (cAMP) metabolism in rat medullary collecting tubules (oMCT) and medullary thick ascending limbs of Henle's loop (mTALH). Gentamicin attenuated AVP-stimulated cAMP accumulation to a greater extent in the mTALH (delta -51%) than in the oMCT (delta -25%). The mechanism of attenuation differed between segments, and could not be attributed to either direct inhibition of adenylate cyclase activity nor direct potentiation of cAMP-phosphodiesterase activity. These data suggest that the gentamicin-induced decrease in renal concentrating ability may be due at least in part to reduced AVP-dependent cAMP accumulation in the oMCT and mTALH.
Insights
Chronic gentamicin treatment impairs kidney function by reducing cyclic AMP (cAMP) signaling in response to arginine 8-vasopressin (AVP). This occurs in specific kidney tubules, affecting the body's ability to concentrate urine.
Area of Science:
- Nephrology
- Pharmacology
- Molecular Biology
Background:
- Arginine 8-vasopressin (AVP) is crucial for regulating renal water reabsorption and urine concentration.
- Gentamicin, an aminoglycoside antibiotic, is known to cause nephrotoxicity, potentially affecting kidney concentrating ability.
- Cyclic AMP (cAMP) acts as a key second messenger in the AVP signaling pathway within renal tubules.
Purpose of the Study:
- To investigate the impact of chronic gentamicin exposure on AVP-stimulated cAMP metabolism in specific rat renal tubule segments.
- To determine the cellular mechanisms underlying gentamicin's effects on cAMP signaling in the outer medullary collecting tubules (oMCT) and medullary thick ascending limbs of Henle's loop (mTALH).
Main Methods:
- Primary rat renal tubule segments (oMCT and mTALH) were isolated and subjected to chronic gentamicin treatment.
- AVP-stimulated cAMP accumulation was measured in these treated segments.
- Adenylate cyclase activity and cAMP-phosphodiesterase activity were assessed to elucidate the mechanism of gentamicin's effect.
Main Results:
- Gentamicin significantly attenuated AVP-stimulated cAMP accumulation in both oMCT and mTALH.
- The inhibitory effect was more pronounced in the mTALH (51% reduction) compared to the oMCT (25% reduction).
- The observed attenuation could not be explained by direct inhibition of adenylate cyclase or potentiation of cAMP-phosphodiesterase.
Conclusions:
- Chronic gentamicin treatment reduces AVP-dependent cAMP accumulation in rat oMCT and mTALH.
- This reduction in cAMP signaling likely contributes to the gentamicin-induced decrease in renal concentrating ability.
- The findings highlight a specific molecular mechanism for gentamicin nephrotoxicity affecting kidney water balance.