The effect of in vitro aging on human lung fibroblast beta-adrenergic receptor density, coupling and response

Abstract

Age-related changes in regulation of receptor response have been observed in several tissues and include regulation of beta-adrenergic receptor (beta-receptor) responses. The role of cellular aging in age-related changes in receptor response is not clear. We have examined the effect of aging in vitro on human fibroblast beta-receptor produce cells of early, middle and late stages corresponding to the following cumulative population doublings: 15–20, 35–45 and > 50, respectively. Fibroblast membrane beta-receptor responses to isoproterenol (ISO, 0.1 mM) did nor to differ between the three stages. Adenylate cyclase response to prostaglandin E 1 (PGE 1, 1 μM), guanosine triphosphate (GTP, 0.1 mM) and 5′-guanylimidodiphosphate (Gpp(NH)p. 0.1 mM) were also similar between the stages. Beta-receptor density (B max) was unaffected by in vitro aging. Beta-receptor agonist affinity, an indication of the capacity or beta-receptor coupling to the nucleotide binding protein (N s), was also unaffected by cell aging. These findings suggest that cellular aging in fibroblasts alone is not accompanied by changes in beta-receptor function.