Supersensitivity of the renal tubule to catecholamines in the chronically denervated canine kidney

Experiments were performed on anesthetized dogs to study whether or not renal tubules of the chronically denervated kidney show supersensitivity toward circulating catecholamines. In one kidney the influence of plasma catecholamines was inhibited by intrarenal administration of the alpha adrenergic receptor blocker phenoxybenzamine (POB, 2 g/min), and renal parameters of the infused kidney were compared to those of the contralateral noninfused organ. Before POB infusion urine flow (V), urinary sodium and potassium excretion (U_NaV, U_KV) as well as clearance of inulin and PAH (GFR, C_PAH) were similar in infused and contralateral kidneys in all the groups studied. In dogs (n=8) with two innervated kidneys POB infusion elevated V and U_NaV by 53±13% and 102±34% (p<0.05). In dogs (n=8) with acute bilateral renal denervation POB administration failed to alter any of the measured parameters. In contrast, V and U_NaV from chronically denervated kidneys (n=7) were increased after POB infusion by 40±9% and 103±34% (p<0.05). Glomerular filtration rate, C_PAH and U_KV were not changed by alpha adrenoceptor blockade in any of the groups. In an additional group of animals (n=8) acute unilateral renal denervation increased V and U_NaV to a significantly higher extent (by 282±85% and 330±106%) than POB administration did in the innervated kidney and elevated U_KV (44±10%), too. It is concluded that supersensitivity to catecholamines developed in renal tubules of the chronically denervated dog kidney and, in consequence, circulating catecholamines at elevated plasma levels caused by surgery were capable of increasing tubular reabsorption of sodium and water.