Iodohydroxybenzylpindolol binding to beta-adrenergic receptors of diabetic and control rat adipocytes' crude membrane.

We have characterized the binding of [125I]-Iodohydroxybenzylpindolol to rat adipocytes' crude membrane. The binding was rapid, reaching equilibrium within 19 min. Binding of [125I]-Iodohydroxybenzylpindolol was saturable with 9 nM. Half-maximal saturation provided an estimated Kd of 2.42 nM. The order for 125IHYP displacement by various compounds was (-)-propranolol (-)-isoproterenol greater than (-)-epinephrine greater than (-)-norepinephrine. [125I]-Iodohydroxybenzylpindolol binding was more sensitive to L-propranolol inhibition in crude membrane prepared from diabetic rat fat cells than in those prepared from controls. The basal cAMP level was identical in diabetic and control rat crude membrane. Isoproterenol increased the cAMP level in diabetic more than in control rats.