Effects of riboflavin deficiency upon age-related changes in beta-adrenergic and adenosine receptor binding in rat adipocytes

The binding of (-)(3H)dihydroalprenolol (DHA) and (-)-N6-(3H)phenyl-isopropyladenosine (PIA) to beta-adrenergic and adenosine receptors, respectively, was determined in membranes of adipocytes isolated from riboflavin-deficient rats and age-matched, pair-fed controls for feeding periods of three to forty weeks. In normal chow-fed animals, the binding of both ligands to receptors markedly decreased in older compared to that in younger animals. In young, riboflavin-deficient animals, DHA binding diminished compared to that in age-matched controls. No further decrease in binding of DHA occurred in older, aged-matched, riboflavin-deficient rats. Riboflavin deficiency did not have any effect on PIA binding in either young or old animals. Thus, in riboflavin deficiency, beta-adrenergic binding in adipocyte membranes from young animals is reduced and the normal age-related decrease in this receptor binding does not occur. By contrast, the binding of PIA to adenosine receptors is lower in older than in younger animals regardless of riboflavin nutriture.