Occurrence of dopaminergic (D(2)) receptors within the rabbit pulmonary circulation.
The pharmacological characteristics and the microanatomical localization of dopamine D(2)-like receptors, or more correctly spiroperidol binding sites, in the rabbit pulmonary circulation were studied using combined marker binding and light microscopy autoradiography with [((3))H]-spiroperidol (spiperone) as marker. The marker was bound to the samples of the pulmonary artery in a manner consistent with the labelling of dopamine D(2)-like receptors with an equilibrium dissociation constant (K(d)) of about 2.4+/-0.07 nmol/l and a maximum density of binding sites of 65+/-4.5 fmol/mg tissue. Samples of bronchial artery show the same results as those of the pulmonary artery. In contrast, binding experiments made with samples of rabbit lung (capillary of the microcirculation), of pulmonary veins and/or of bronchial veins did not allow the evaluation of specific binding.Autoradiography, observed with light microscopy, showed the development of specific silver grains within the whole wall of extraparenchymal branches of the pulmonary artery and/or of the bronchial artery. Development of silver grains was inhibited by compounds active on the dopamine receptors. The greater sensitivity to displacement by domperidone, haloperidol, and bromocriptine than to displacement by N-propyl-nor-apomorphine, quinpirole and clozapine suggests that the binding sites observed in extraparenchymal, large and medium-sized branches of the rabbit pulmonary and bronchial arteries belong, likely, to the dopamine D(2) receptor subtype. Quantitative analysis of images let us count the amount of these receptors in many samples of the pulmonary and/or bronchial arteries.
Bruzzone
Paolo
P
Department of Surgery (2nd Division), University La Sapienza, via Alfonso Borelli 50, 00161 Rome, Italy.
D'Andrea
Vito
V
Motta
Cecilia
C
Cavallotti
Carlo
C
D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive / Q000187:drug effects / Q000502:physiology; D001981:Bronchial Arteries / Q000737:chemistry / Q000187:drug effects; D002196:Capillaries / Q000737:chemistry; D018492:Dopamine Antagonists / Q000378:metabolism; D008297:Male; D011651:Pulmonary Artery / Q000737:chemistry / Q000187:drug effects; D011652:Pulmonary Circulation / Q000187:drug effects; D011667:Pulmonary Veins / Q000737:chemistry; D011817:Rabbits; D017448:Receptors, Dopamine D2 / Q000032:analysis* / Q000187:drug effects; D013134:Spiperone / Q000378:metabolism; D014316:Tritium; D014680:Veins / Q000737:chemistry / Q000187:drug effects
D018492:Dopamine Antagonists; D017448:Receptors, Dopamine D2; D014316:Tritium; D013134:Spiperone