title: Response of pineal beta-adrenoceptors in different breeds of sheep to immunization against selected steroids.
abstract: Active immunization of Merino and Wiltshire Horn X Merino cross-bred sheep against a range of gonadal steroids has revealed that pineal beta-adrenoceptors in both breeds are sensitive to hormonal modification by androgens, but only in the less seasonal, non-shedding Merino do these receptors appear to be sensitive to regulation by estrogens. Neither breed showed sensitivity of its pineal beta-adrenoceptors to active immunization against the pineal hormone melatonin under either normal or reversed photoperiod treatment. These results (a) suggest that pineal related seasonal differences between the breeds (i.e. wool shedding and/or reproductive function) may reside in differential sensitivity of the pineal gland to regulation by specific circulating steroid hormones, and (b) indicate an absence of end-product regulation of beta-adrenoceptor-mediated pineal melatonin biosynthesis in both seasonally shedding and non-shedding sheep.
mesh_terms: D000728:Androgens / Q000502:physiology; D000818:Animals; D004967:Estrogens / Q000502:physiology; D004971:Estrus; D005260:Female; D012739:Gonadal Steroid Hormones / Q000502:physiology*; D006801:Humans; D007114:Immunization; D008550:Melatonin / Q000502:physiology; D010870:Pineal Gland / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D012621:Seasons; D012756:Sheep; D013045:Species Specificity
chemical_list: D000728:Androgens; D004967:Estrogens; D012739:Gonadal Steroid Hormones; D011943:Receptors, Adrenergic, beta; D008550:Melatonin