Alpha 1-adrenoceptor mediation of urinary bicarbonate excretion.
The adrenoceptor mechanism that mediates the reduction of urinary sodium (UNa V) and bicarbonate (UHCO3 V) excretion during 1.0-Hz renal nerve stimulation (RNS) was evaluated in 21 anesthetized dogs. In each animal RNS decreased UNa V and UHCO3 V without changing mean arterial pressure, renal blood flow, or glomerular filtration rate. After these initial responses, dogs were administered phentolamine [2.0 micrograms.kg-1.min-1 intrarenal artery (ira); n = 7], prazosin (0.7 micrograms.kg-1.min-1 ira; n = 5), (+/- )-propranolol (2.0 micrograms.kg-1.min-1 ira; n = 4), or atenolol (50 mg/kg iv; n = 5) and the renal responses to RNS were again tested. Both the antinatriuretic response and reduction of UHCO3 V during RNS were abolished by alpha 1/alpha 2-adrenoceptor blockade with phentolamine and by alpha 1-adrenoceptor antagonism with prazosin. beta-Adrenoceptor blockade with (+/- )-propranolol (beta 1/beta 2) or atenolol (beta 1) did not alter either the decrease in UNa V or UHCO3 V after RNS. These results provide further evidence that, during low-frequency RNS, reduction of UNa V is mediated in part by carbonic anhydrase-dependent bicarbonate reabsorption. These antinatriuretic responses and decreases in UHCO3 V during 1.0-Hz RNS are mediated by adrenergic neurotransmitter stimulation of alpha 1-adrenoceptors.
Osborn
J L
JL
Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
Harland
R W
RW
D000818:Animals; D001639:Bicarbonates / Q000652:urine*; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects; D007668:Kidney / Q000294:innervation / Q000502:physiology*; D008297:Male; D010646:Phentolamine / Q000494:pharmacology*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D012016:Reference Values; D012079:Renal Circulation / Q000187:drug effects; D012964:Sodium / Q000652:urine
D001639:Bicarbonates; D011942:Receptors, Adrenergic, alpha; D012964:Sodium; D010646:Phentolamine