Distribution of beta-adrenoceptor subtypes in gastrointestinal tract of nondiabetic and diabetic BB rats - A longitudinal study

The effects of aging and diabetes on the distribution of beta-adrenoceptor subtypes in the gut were investigated in the BE rat, [I-125]Cyanopindolol binding to 10-mu m sections was evaluated using film autoradiography, Cyanopindolol binding to beta-, beta(1)-, and beta(2)-adrenoceptors was displaced by 1 mu M propranolol, 50 nhl ICI-89-406, and 100 nM ICI-118-551, respectively. beta-Adrenoceptor binding was highest in the circular muscle of proximal colon and lowest in the pylorus of 4- to 5-month-old rats. Aging (8- to 10-month-old vs, 4- to 5-month-old rats) was associated with increased beta-adrenoceptor binding in the pylorus and reduced binding in the proximal colon. Diabetes had a time-dependent effect on the level of beta-adrenoceptor binding. It was increased in the antral and pyloric stomach but longer periods of diabetes caused a reduction in beta-adrenoceptor binding in the pylorus. Those in the intestine were reduced time-dependently and involved beta(1)- or beta(2)-adrenoceptors or both.