Hormonal influence on expression and functionality of α1-adrenoceptor in rat submandibular gland

In this work, we characterized α1-adrenoceptor expression and functionality in rat submandibular gland. Cumulative dose–response curve of methoxamine was constructed to determine the peroxidase secretion by glands from proestrous, estrous, metestrous and diestrous rats. They were compared to those from animals untreated or treated with sex hormones, estradiol and progesterone. The sensitivity of glands to an α1-adrenoceptor agonist varied depending on hormonal state, i.e. glands from proestrous and estrous were more sensitive to the stimulatory action of methoxamine than those from metestrous, diestrous and ovariectomised animals. The efficacy of the α1 agonist was enhanced in glands from ovariectomised estrogen-treated rats but it was ineffective in glands from ovariectomised progesterone-treated rats. The functional studies correlated with 3H-prazosin binding assays in which estrogen increased α1-adrenoceptor density while progesterone decreased it. The results demonstrated that α1-adrenoceptor expression and functionality in rat submandibular glands are apparently under hormonal control and probably represent other examples of bidirectional interactions between neuronal and exocrine systems.