Glomerulotubular balance during renal sympathetic stimulation.
In volume-expanded dogs receiving ethacrynic acid, a linear relationship, glomerulotubular balance (GTB), applies between the remaining sodium reabsorption and the glomerular filtration rate (GFR) during mechanical aortic constriction. To examine whether GTB applies during sympathetic stimulation, the GFR was progressively reduced by 70-75% in anaesthetized dogs by renal nerve stimulation, intrarenal norepinephrine infusion or by selective stimulation of alpha-adrenoceptors by intrarenal methoxamine infusion. Linear relationships (GTB) were obtained (r greater than 0.9). Reabsorption was not different during the various kinds of sympathetic stimulation, but less than during aortic constriction; the largest difference in NaCl reabsorption at comparable GFR amounted to 10-15% and was obtained 30-40% below control GFR, whereas inhibition of NaHCO3 reabsorption was uncertain. To inhibit NaHCO3 reabsorption and associated NaCl reabsorption in the proximal tubules, acetazolamide (30 mg kg-1) was administered instead of ethacrynic acid. No difference in reabsorption was observed at comparable GFR during norepinephrine infusion and mechanical aortic constriction. Hence, GTB applies during sympathetic stimulation. Compared with data obtained during aortic constriction, alpha-adrenergic stimulation reduces proximal reabsorption of NaCl and, possibly, NaHCO3 and exerts no effect on distal transcellular NaCl reabsorption.
Hartmann
A
A
Langberg
H
H
Holdaas
H
H
Kiil
F
F
D000086:Acetazolamide / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D004573:Electrolytes / Q000378:metabolism; D004976:Ethacrynic Acid / Q000494:pharmacology; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D007668:Kidney / Q000294:innervation*; D007678:Kidney Glomerulus / Q000502:physiology*; D007684:Kidney Tubules / Q000502:physiology*; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D012965:Sodium Chloride / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D004573:Electrolytes; D012965:Sodium Chloride; D008729:Methoxamine; D004976:Ethacrynic Acid; D000086:Acetazolamide; D009638:Norepinephrine