Meeting Abstract

11.5  Jan. 4  Regulation of interrenal steroidogenic mRNAs in the elasmobranchs Dasyatis sabina and Potamotrygon motoro EVANS, A.N.*; IP, Y.K.; NUNEZ, B.S.; University of Texas Marine Science Institute; National University of Singapore; University of Texas Marine Science Institute aevans@utmsi.utexas.edu

The steroidogenic acute regulatory protein (StAR) is critical for the production of steroid hormones, delivering cholesterol to the rate-limiting steroidogenic enzyme, cholesterol side-chain cleavage (SCC); the production of both sex steroids and corticosteroids requires further conversion by 3β-hydroxysteroid dehydrogenase (3β-HSD). Regulation of the genes encoding these enzymes in steroidogenic tissues is therefore necessary for the timely production of steroids required for vital physiological processes. We examined the regulation of StAR, SCC and 3β-HSD mRNA in the freshwater stingray P. motoro and euryhaline stingray D. sabina using quantitative PCR. To examine the effects of environmental salinity on mRNAs encoding these primary steroidogenic enzymes, freshwater P. motoro were challenged with 10 ppt salinity for one week. We then determined levels of interrenal gland StAR, SCC and 3β-HSD mRNAs. There was no significant difference in the relative levels of interrenal steroidogenic mRNAs in control vs. experimental animals; however lack of statistical significance was due to high levels of StAR and SCC mRNA in a single 10 ppt individual. Relative basal levels of StAR and SCC mRNA expression were determined in interrenal glands taken from freshwater and saltwater D. sabina. In addition, the in vitro regulation of StAR and SCC mRNAs by hormones involved in osmoregulation (angiotensin II and C-type natriuretic peptide) and stress (adrenocorticotropic hormone and 1α-hydroxycorticosterone) was investigated in D. sabina steroidogenic tissues. Future research will examine the role of interrenal steroidogenesis in the acclimation of D. sabina to fresh water.