Beta-adrenoceptors in the extraorbital lacrimal gland of the Syrian hamster. Characterization with [125I]-iodopindolol and evidence of sexual dimorphism.
Saturation and competition experiments with the radiolabeled beta-adrenergic antagonist (--)-[125I]-iodopindolol were used to characterized beta-adrenoceptor density (Bmax) and receptor affinity in the extraorbital lacrimal gland of male and female Syrian hamsters. Specific binding to the receptor was saturable. Scatchard analysis of saturation isotherms revealed a single population of receptor sites. Male glands had a significantly higher Bmax (38.9 +/- 5.0 vs. 23.3 +/- 2.1 fmol/mg protein, means +/- SEM, p less than 0.02) and receptor affinity (expressed in a lower dissociation constant Kd: 0.065 +/- 0.013 vs. 0.120 +/- 0.015 nM, p less than 0.02) than female glands. Binding of the radiolabeled ligand in competition with various adrenergic antagonists showed the receptor to be stereospecific and of the beta 2-subtype.