ALTERATIONS OF SUBTYPES OF CARDIAC ADRENOCEPTORS IN OLD RAT

AIM: To determine alterations of subtypes of adrenoceptors in senescen ce. METHODS: Heart membrane preparations were made from 3- and 25-mont h old Wistar alpha(1)- and beta-adrenoceptors were measured by radioli gand, I-125-BE2254 and I-125-pindolol, binding assays, respectively. R ESULTS: In the old rat heart, alpha(1)- and beta-adrenoceptor densitie s were declined from the young rats of 119+/-4 and 45.9+/-1.9 pmol L(- 1) to 70+/-6 and 36.4+/-1.6 pmol L(-1) (P<0.01), with a greater change in alpha(1)-AR and in beta-AR. The ratio of alpha(1A)/alpha(1B) subty pes was decreased from the young rats of 39/61 to the old rats of 26/7 4 (P<0.05). CONCLUSION: The cardiac adrenoceptors are decreased with d ifferent extents in the different subtypes in old rats.