Functional Roles of Estradiol in the Olfactory and Vomeronasal Mucosae of Mammals: A Working Hypothesis

Abstract

It has been known that androgens and estrogens, which are referred to as sex steroids, make many effects on two major nasal chemosensory mucosae such as olfactory mucosa and vomeronasal organ. Our studies conducted in rodents have demonstrated that two of the constituent cells in the olfactory mucosa, sustentacular cells and acinar cells in the associated glands of the olfactory mucosa, Bowman’s glands, express four different enzymes involved in the biosynthesis of estradiol-17β (E2). Furthermore, our ongoing study has shown that olfactory sensory cells contain immunoreactivity for an estrogen receptor (beta-type). In case of vomeronasal organ, vomeronasal sensory cells express two enzymes that catalyze conversion of E2 and estrone, and that of testosterone and androstenedione. In addition, vomeronasal sensory cells contain an estrogen receptor (alpha-type). These results strongly suggest that de novo synthesis of E2 and metabolism of E2 take place in the olfactory mucosa and vomeronasal organ, respectively. With special emphasis of subcellular characteristics of steroid-producing cells, such as presence of large amount of smooth endoplasmic reticulum and vesicular mitochondria, we will introduce our findings and present working hypotheses for E2 functions in the olfactory mucosa and vomeronasal organ.