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Isoproterenol increases Ca, Mg, and NaCl reabsorption in mouse thick ascending limb
C Bailly1, M Imbert-Teboul, N Roinel
1Laboratoire de Physiologie Rénale, Faculté Xavier Bichat, Université Paris, France.
Abstract:
The effect of isoproterenol (Iso) on tubular transport in the thick ascending limb of Henle's loop (TAL) was investigated by in vitro microperfusion of MTAL (medullary) and CTAL (cortical) from White Swiss mouse kidney. The pattern of activation of adenylate cyclase along the distal tubule was investigated in this strain: results indicated that Iso stimulated adenylate cyclase fivefold in MTAL and ninefold in CTAL. Data from microperfusion experiments showed that Iso (10(-7) M in the bath) significantly and reversibly increased Ca and Mg reabsorption in CTAL. No net transport of Ca and Mg was observed in MTAL whether Iso was present or not. With regard to Na and Cl, Iso significantly stimulated their reabsorption in both segments and increased the transepithelial voltage in MTAL. Iso abolished K reabsorption in MTAL and induced a net K secretion in CTAL, the latter effect being also observed with 10(-9) M of Iso. When applied on CTAL, propranolol (10(-6) M in the bath) inhibited all these effects. These data indicate that beta-adrenergic agonists are involved in the multihormonal modulation of the TAL function.
Insights
Isoproterenol (Iso) affects kidney tubules by increasing calcium, magnesium, and sodium reabsorption in the thick ascending limb (TAL). It also alters potassium transport, indicating beta-adrenergic agonists modulate TAL function.
Area of Science:
- Nephrology
- Renal Physiology
- Pharmacology
Background:
- The thick ascending limb (TAL) of Henle's loop plays a crucial role in renal salt and water reabsorption.
- Hormonal regulation of tubular transport is essential for maintaining kidney function and homeostasis.
Purpose of the Study:
- To investigate the effects of isoproterenol (Iso), a beta-adrenergic agonist, on tubular transport in the medullary (MTAL) and cortical (CTAL) segments of the mouse kidney TAL.
- To explore the role of adenylate cyclase activation in mediating these effects.
Main Methods:
- In vitro microperfusion of mouse kidney MTAL and CTAL segments.
- Measurement of adenylate cyclase activity.
- Assessment of net transport of electrolytes (Ca, Mg, Na, Cl, K) and transepithelial voltage.
Main Results:
- Isoproterenol significantly stimulated adenylate cyclase in both MTAL and CTAL.
- Iso increased Ca and Mg reabsorption in CTAL but not MTAL.
- Iso enhanced Na and Cl reabsorption in both segments and increased transepithelial voltage in MTAL.
- Iso abolished K reabsorption in MTAL and induced K secretion in CTAL.
- Propranolol blocked all observed effects of Iso on CTAL.
Conclusions:
- Beta-adrenergic agonists, like isoproterenol, play a significant role in the hormonal regulation of TAL function.
- These findings highlight the involvement of beta-adrenergic signaling in modulating electrolyte transport within the kidney TAL.