RESUMEN
The specific binding of 125I-(-)-cyanopindolol (125I-(-)-CYP) to homogenates and cryostat sections of rat nasal mucosa was saturable, stereoselective and of high affinity (Kd = 5.0 +/- 0.4 pM. Bmax = 204 +/- 12 fmol/mg protein and Kd = 7.2 +/- 0.7 pM; Bmax = 15 +/- 1 fmol/mg protein respectively). The subtype-selective antagonists, LK203-030 and ICI118,551, inhibited specific 125I-(-)-CYP binding according to a two-binding site model, indicating the presence of 57 and 45% beta 1-adrenoceptors in homogenates and cryostat sections, respectively. Competition of isoprenaline for antagonist binding to homogenates demonstrated 30 +/- 3% high-affinity agonist binding sites. A steepening of the curve was observed in presence of guanine nucleotides. In vitro labelling of cryostat sections of rat nasal mucosa was combined with autoradiography. The autoradiographs generated after incubation with 20 pM 125I-(-)-CYP showed specific labelling of the epithelium and glandular excretory ducts. It appeared from autoradiographs generated with subtype-selective antagonists in addition to the radioligand that beta 1- and beta 2-adrenoceptors were present in both structures.
Asunto(s)
Mucosa Nasal/metabolismo , Receptores Adrenérgicos beta/análisis , Animales , Autorradiografía , Técnicas In Vitro , Radioisótopos de Yodo , Yodocianopindolol , Isoproterenol/farmacología , Cinética , Mucosa Nasal/anatomía & histología , Pindolol/análogos & derivados , Ensayo de Unión Radioligante , Ratas , Ratas Endogámicas , EstereoisomerismoRESUMEN
The distribution of beta-adrenergic receptors in rat nasal glands has been investigated with the use of an in vitro autoradiographic technique. Radioligand binding studies indicated that [125I]cyanopindolol binds specifically to beta-adrenergic receptors in cryostat sections of these glands. Autoradiograms generated after incubation with 0.02 nM [125I]cyanopindolol and dipping in nuclear K2 emulsion, showed specific labelling of the striated excretory ducts. These in vitro observations suggest a sympathetic control of the ion and water content of the glandular secretion.