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Characterization and regulation of. beta. /sub 2/-adrenergic receptors in rat vas deferens

Thesis/Dissertation ·
OSTI ID:7023958

..beta../sub 2/-Adrenergic receptors in rat vas deferens were examined by measuring the binding of /sup 125/I-pindolol (/sup 125/IPIN) to membrane preparations and the inhibition of evoked contractions in intact tissues. /sup 125/IPIN labeled a single class of binding sites with mass action kinetics. Affinity constants for ..beta..-adrenergic receptor antagonists calculated from both binding and functional experiments agreed well, suggesting that /sup 125/IPIN labels the functional ..beta../sub 2/-adrenergic receptor. n-Bromoacetylalprenololmenthane (BAAM) was used to decrease receptor density so that agonist affinity constants could be determined functionally. Treatment of tissues with BAAM decreased the functional potencies of agonists. Higher concentrations of BAAM decreased the maximum tissue response. Affinity constants for agonists calculated after BAAM treatment were compared to affinity constants determined from binding studies done under conditions designed to promote high or low affinity agonist binding. Functional affinity constants for isoproterenol and salbutamol agreed with the low affinity binding constants, suggesting that the low affinity form of the receptor initiates the functional response. Because acute denervation of vasa deferentia did not alter the density of /sup 125/IPIN binding sites, the sites are probably post-junctional. Chronic infusion of isoproterenol reduced the potency of isoproterenol, the maximum tissue response, and the receptor density. These results suggest that ..beta..-adrenergic receptor density and responsiveness in rat vas deferens are not affected by removing catecholamine sources, but receptor density and responsiveness can be decreased by increasing agonist concentration at the receptor.

Research Organization:
Emory Univ., Atlanta, GA (USA)
OSTI ID:
7023958
Country of Publication:
United States
Language:
English

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Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
AZAARENES
AZOLES
BETA DECAY RADIOISOTOPES
BIOCHEMISTRY
BODY
CHEMISTRY
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
GONADS
HETEROCYCLIC COMPOUNDS
INDOLES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MALE GENITALS
MAMMALS
MEMBRANE PROTEINS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PROTEINS
PYRROLES
RADIOISOTOPES
RADIORECEPTOR ASSAY
RATS
RECEPTORS
RODENTS
SYMPATHOMIMETICS
TESTES
TRACER TECHNIQUES
VERTEBRATES