Characterization of β‐adrenoceptors in the syrian hamster harderian gland: Sexual differences and effects of either castration of superior cervical ganglionectomy

Scatchard analysis of saturation isotherms of [¹²⁵I]‐iodopindolol was used to characterize β‐adrenoceptor density (B_max) and affinity constant (K_d) in female and male hamster Harderian glands. Single‐point experiments were also completed in intact females, intact males, and castrated or superior cervical ganglionectomized males. Scatchard analysis described a single population of binding sites with a B_max of 292.2 ± 45.1 fmol/mg protein (X ± SEM, n = 6) in females and 18.2 ± 3.0 fmol/mg protein (n = 6, P < 0.001) in males. The affinity also varied significantly (P < 0.05) with a K_d of 1.08 ± 0.18 versus 0.26 + 0.05 nM (n = 6) in the Harderian gland of females and males, respectively. Single‐point [¹²⁵I]‐IPIN (400 pM) binding values in females were 67.3 ± 4.0, in intact males were 12.8 ± 3.2, and in castrated males were 31.2 ± 4.2 fmol/mg protein (n = 7–9). Superior cervical ganglionectomy induced no significant changes in receptor binding. The results indicate pronounced sexual differences in the density and affinity of β‐adrenoceptors in the hamster Harderian gland, which may be sex hormone dependent.