Abstract
Dopamine induces renal vasodilatation in the mature canine. Low affinity DR in renal artery and high affinity DR in glomerulus have been reported but no measurements have been made on the arterial segments interposed between these two structures. These experiments characterize, for the first time, DR in dog IRA by radioligand binding using 3H-haloperidol (H). IRA were dissected and homogenized. Specific H binding was defined as the difference in binding in the presence and absence of 30 uM cis-flupenthixol (a potent dopamine antagonist). Kinetic analysis revealed a binding site that saturated in 3 min. and remained at steady state for over 1 hr. The dissociation constant (Kd) calculated from kinetic data was 8 nM. Competition studies were consistent for DR: LY-141865>YM-09151>cis-flupenthixol=(-)-propranolol>metoclopramide>prazosin>SKF 82526-J and stereoselective: (+)-apomorphine >>(-)-apomorphine. Rosenthal plots of saturation data revealed biphasic curves suggestive of multiple classes of binding sites. The high affinity DR site had a Kd of 2.3±1.0 nM and a maximum receptor density (Bmax) of 19.5±5.0 fmol/mg protein (±SEM, n=5). For the low affinity site the Kd was 31.8±1.7 nM and the Bmax was 92±20 fmol/mg protein (n=5). These results suggest that the adult canine IRA contain specific DR. The specific DR-2 antagonist YM-09151 and the DR-2 agonist LY-141865 were more potent than the relatively DR-1 selective antagonist cis-flupenthixol and DR-1 agonist SKF 82526-J respectively suggesting that the predominant DR in the canine IRA is of the DR-2 subtype.
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Felder, R., Worthington, J. & Jose, P. DOPAMINE RECEPTORS (DR) IN DOG INTRARENAL ARTERIES(IRA). Pediatr Res 18 (Suppl 4), 361 (1984). https://doi.org/10.1203/00006450-198404001-01607
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DOI: https://doi.org/10.1203/00006450-198404001-01607