Characterisation of beta 1 and beta 2 adrenoceptor subtypes in the atrioventricular node of diabetic rat hearts by quantitative autoradiography.
OBJECTIVE
The aim was to determine whether the changes in beta adrenoceptors might be involved in the conduction system of diabetic rat hearts.


METHODS
beta Adrenoceptors in the atrioventricular node of diabetic hearts and controls were characterised by quantitative autoradiography.


METHODS
The experiments were performed in five male Wistar rats injected with streptozotocin (65 mg.kg-1) to induce diabetes and in five rats injected with vehicle alone.


RESULTS
125I-iodocyanopindolol binding sites decreased by 25% in atrioventricular node of diabetic hearts compared to control hearts without a significant change in the affinity. The selective beta 1 adrenoceptor antagonist CGP20712A (100 nmol.litre-1) displaced about 30% and 50% of the total atrioventricular node binding sites in diabetic and control hearts, respectively.


CONCLUSIONS
These data support the concept that a decrease in beta adrenoceptors, mainly of the beta 1 subtype, in the atrioventricular node may play an important role in the cardiac conduction disturbance of diabetic animals.
Saito
K
K
Health Service Centre, National Institute of Fitness and Sports, Kanoya, Japan.
Kuroda
A
A
Tanaka
H
H
D000818:Animals; D001283:Atrioventricular Node / Q000737:chemistry*; D001345:Autoradiography; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000737:chemistry*
D011943:Receptors, Adrenergic, beta