| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Regular Article |
a Department of Marine Science, Marine Science Institute, University of Texas at Austin, Port Aransas, Texas 78373-5015
ABSTRACT
Changes in ovarian maturation-inducing steroid (MIS; 17,20ß,21-trihydroxy-4-pregnen-3-one [20ß-S]) membrane receptor concentrations during the reproductive cycle were investigated in spotted seatrout (Cynoscion nebulosus) captured at their spawning grounds. Ovarian receptor concentrations increased gradually during ovarian recrudescence and subsequently increased rapidly during oocyte maturation, reaching 3.5-fold the prematuration values by the beginning of ovulation. The significant elevation of receptor concentrations by the germinal vesicle migration stage of oocyte maturation was accompanied by increases in circulating levels of gonadotropin (LH, GTH II) and MIS (20ß-S). The regulation and physiological significance of the increase in ovarian MIS membrane receptor concentrations were investigated in a double in vitro incubation system. Incubation of fully grown, follicle-enclosed oocytes with hCG (10 IU/ml) for 6 h caused a two- to fourfold increase in oocyte and ovarian MIS receptor concentrations and the development of oocyte maturational competence (OMC; ability to complete oocyte maturation in vitro in response to exogenous 20ß-S in a second incubation). Both upregulation of the MIS receptor and development of OMC in response to gonadotropin were blocked by coincubation with actinomycin D or cycloheximide, which are inhibitors of mRNA and protein synthesis, respectively, but not by cyanoketone, which is an inhibitor of 3ß-hydroxysteroid dehydrogenase-dependent steroid synthesis. Incubation with a variety of steroids, including 20ß-S, failed to increase receptor concentrations or to induce OMC, further supporting a steroid-independent mechanism of gonadotropin action. In contrast, insulin-like growth factor I (IGF-I) mimicked the actions of gonadotropin, which suggests IGF-I may be a component of the hormone signaling pathway. A close correlation was found between the relative increase in MIS receptor concentrations and the percentage of oocytes that became maturationally competent after treatment with different concentrations of gonadotropins and drugs that elevate cAMP levels. The finding that upregulation of the MIS receptor in response to gonadotropin and other treatments is invariably associated with the development of OMC indicates that these two processes are intimately related, and it suggests that the increase in MIS receptor concentrations is a critical regulatory step in the hormonal control of oocyte maturation.
1 Supported by PHS grant ES04214 to P.T.
2 Correspondence: Peter Thomas, Marine Science Institute, University of Texas at Austin, 750 Channel View Dr., Port Aransas, TX 78373-5015. FAX: 361 749 6777; thomas{at}utmsi.utexas.edu
3 Current address: Department of Fisheries and Oceans, 4160 Marine Dr., West Vancouver, BC, V7V 1N6 Canada.
4 Current address: Department of Internal Medicine, Yale University, School of Medicine, VA Medical Center, West Haven, CT 06516.
This article has been cited by other articles:
|
|
 |
|
  M. C. Pace and P. Thomas Steroid-Induced Oocyte Maturation in Atlantic Croaker (Micropogonias undulatus) Is Dependent on Activation of the Phosphatidylinositol 3-Kinase/Akt Signal Transduction Pathway Biol Reprod, November 1, 2005; 73(5): 988 - 996. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W.-K. So, H.-F. Kwok, and W. Ge Zebrafish Gonadotropins and Their Receptors: II. Cloning and Characterization of Zebrafish Follicle-Stimulating Hormone and Luteinizing Hormone Subunits--Their Spatial-Temporal Expression Patterns and Receptor Specificity Biol Reprod, June 1, 2005; 72(6): 1382 - 1396. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. M. Weber and C. V. Sullivan Insulin-Like Growth Factor-I Induces Oocyte Maturational Competence but Not Meiotic Resumption in White Bass (Morone chrysops) Follicles In Vitro: Evidence for Rapid Evolution of Insulin-Like Growth Factor Action Biol Reprod, May 1, 2005; 72(5): 1177 - 1186. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Wang and W. Ge Spatial Expression Patterns of Activin and Its Signaling System in the Zebrafish Ovarian Follicle: Evidence for Paracrine Action of Activin on the Oocytes Biol Reprod, December 1, 2003; 69(6): 1998 - 2006. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. M. LOSEL, E. FALKENSTEIN, M. FEURING, A. SCHULTZ, H.-C. TILLMANN, K. ROSSOL-HASEROTH, and M. WEHLING Nongenomic Steroid Action: Controversies, Questions, and Answers Physiol Rev, July 1, 2003; 83(3): 965 - 1016. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Zhu, C. D. Rice, Y. Pang, M. Pace, and P. Thomas From the Cover: Cloning, expression, and characterization of a membrane progestin receptor and evidence it is an intermediary in meiotic maturation of fish oocytes PNAS, March 4, 2003; 100(5): 2231 - 2236. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Patino, G. Yoshizaki, D. Bolamba, and P. Thomas Role of Arachidonic Acid and Protein Kinase C During Maturation-Inducing Hormone-Dependent Meiotic Resumption and Ovulation in Ovarian Follicles of Atlantic Croaker Biol Reprod, February 1, 2003; 68(2): 516 - 523. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Pang and W. Ge Gonadotropin and Activin Enhance Maturational Competence of Oocytes in the Zebrafish (Danio rerio) Biol Reprod, February 1, 2002; 66(2): 259 - 265. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
