Hormonal influence on expression and functionality of alpha1-adrenoceptor in rat submandibular gland

In this work, we characterized alpha(1)-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 alpha(1)-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 alpha(1) 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 alpha(1)-adrenoceptor density while progesterone decreased it. The results demonstrated that alpha(1)-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.