title: Sodium regulation of alpha 2-adrenoceptor-agonist interactions in renal membranes of young and old Dahl rats.
abstract: Systolic blood pressure, the affinity and density of the alpha 2-adrenoceptors, Na+ effect on alpha 2-adrenoceptors as measured by specific [3H]yohimbine binding, and Na+ regulation of alpha 2-adrenoceptor-agonist interactions were studied in 6 week and 9 month old inbred salt sensitive (S) and inbred salt-resistant (R) rats. The systolic blood pressure of 6 week old S and R rats was not significantly different, while the systolic blood pressure of 9 month old S rats was higher than the age-matched R rats. The affinity of the alpha 2-adrenoceptors for yohimbine was the same in the 6 week old S and R rats but it was 2-fold less in the 9 month old S rats compared to the age-matched R rats. In the 6 week old rats, the number of alpha 2-adrenoceptors (Bmax) was significantly higher in the S rats than in the R rats; whereas, in the 9 month old rats, the alpha 2-adrenoceptors were 2.6 times higher in the S rats than the age-matched R rats. Na+, up to 80 mM, did not modify the number of alpha 2-adrenoceptors in the 6 week and 9 month old S and R rats. However, Na+ reduced the affinity of the alpha 2-adrenoceptors for epinephrine and this effect of Na+ was found to be the same in the 6 week and 9 month old S and R rats. These findings suggest that Na+ regulation of alpha 2-adrenoceptor-agonist interactions was not altered with age and it was found to be similar in prehypertensive rats and rats with severe hypertension; further, the resistance of R rats to salt-induced hypertension was not due to the absence of Na+ binding component in the alpha 2-adrenoceptor-adenylate cyclase complex.
authors.affiliation: Department of Pharmacology, Medical College of Ohio, Toledo 43699.
authors.forename: S M
authors.initials: SM
authors.lastname: Periyasamy
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008024:Ligands; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology; D015016:Yohimbine / Q000378:metabolism
chemical_list: D000316:Adrenergic alpha-Agonists; D008024:Ligands; D015016:Yohimbine; D012965:Sodium Chloride; D012964:Sodium; D004837:Epinephrine