Binding of [3H]befunolol to beta-adrenoceptors in cardiac muscles of fetal and neonatal rat |
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Authors: | K Koike H Tanaka K Shigenobu I Takayanagi |
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Affiliation: | Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan. |
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Abstract: | Characterization of beta-adrenoceptors was studied in heart muscles of rat fetus and neonate. The results of binding assay with [3H]befunolol, a beta-adrenergic partial agonist, to membrane fractions from rat heart muscles indicate that beta-adrenoceptors contain two different affinity sites. In the presence of 5'-guanylylimidodiphosphate, the low affinity site was reduced, while the high affinity site was not affected. The dissociation constants for both sites did not change during pre- and post-natal development. But the maximum binding sites for both sites decreased slightly but significantly (p less than 0.05) during development. A 10-fold decrease in norepinephrine sensitivity and isoprenaline sensitivity during pre- and post-natal development was not explained by the slight decrease in the maximum binding sites. |
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