Expression of the insulin-like growth factor and insulin systems in the luteinizing macaque ovarian follicle
Received 23 April 2008; received in revised form 18 December 2008; accepted 18 December 2008. published online 24 February 2009.
Objective
To determine intrafollicular hormone levels and characterize the mRNA expression of the insulin-like growth factor (IGF) receptors, IGF binding proteins (IGFBP), and pregnancy-associated plasma protein-A (PAPP-A) in granulosa cells before and after an ovulatory hCG stimulus.
Design
Experimental animal study.
Setting
Academic medical center.
Animal(s)
Adult rhesus macaques.
Intervention(s)
Animals received exogenous FSH to promote the development of multiple preovulatory follicles. Follicles were aspirated before (0 hours) or 3, 6, 12, or 24 hours after an ovulatory hCG bolus.
Main Outcome Measure(s)
IGF1, IGF2, and insulin levels in follicular fluid were determined by radioimmunoassay. Messenger RNA (mRNA) levels in granulosa cells were determined by real-time reverse transcriptase–polymerase chain reaction. IGFBPs and PAPP-A in follicular fluid were determined by Western blot analysis and enzyme-linked immunosorbent assay.
Result(s)
IGF1, IGF2, and insulin in follicular fluid did not change during luteinization. IGF1R, IGFBP1, and IGFBP2 mRNAs were unchanged by hCG. IGF2R, IGFBP3, -5, and -6 and PAPP-A mRNA levels increased after hCG administration, while insulin receptor and IGFBP4 mRNA levels decreased after hCG administration. IGFBP3 and -6 and PAPP-A protein increased after hCG administration.
Conclusion(s)
Dynamic changes in the expression of the IGFBPs and PAPP-A suggest tight regulation of IGF action during ovulation and corpus luteum formation.
aDepartment of Biology, Loyola College in Maryland, Baltimore, Maryland
bDepartment of Obstetrics, Gynecology, and Reproductive Sciences, University of Maryland School of Medicine, Baltimore, Maryland
cCalifornia National Primate Research Center, Davis, California
Reprint requests: Charles L. Chaffin, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Maryland School of Medicine, Baltimore, Maryland 21201 (FAX: 410–706–5747).
R.S.B. has nothing to disclose. S.M. has nothing to disclose. M.P. has nothing to disclose. C.A.V. has nothing to disclose. C.L.C. has nothing to disclose.
This research was supported in part by National Institutes of Health grant nos. HD043358 (to CLC), RR13439 (to CAV), and RR00169 (to the California National Primate Research Center).
ABSTRACT