The pre-ovulatory surge of gonadotrophins triggers a marked and obligatory increase in follicular prostaglandin synthesis prior to ovulation, and the cyclooxygenase (COX) enzyme is a key rate-limiting step in the biosynthesis of prostaglandins. In the early 1990s, the pre-ovulatory rise in follicular prostaglandin synthesis was shown to result from the selective induction of a novel COX isoform, now referred to as COX-2. Differences in the time-course of COX-2 induction in species with a short versus a long ovulatory process suggest that the enzyme could be a molecular determinant that sets the alarm of the mammalian ovulatory clock. Some of the fine molecular mechanisms involved in the transcriptional activation of the COX-2 gene in granulosa cells have also been elucidated. The binding of trans-activating upstream stimulatory factors (USF) to a consensus E-box cis-element in the proximal region of the promoter was shown to play a predominant role in COX-2 transcription. Studies showed that COX-2 expression could also serve as a valuable marker for follicular commitment to ovulation during hyperstimulatory cycles. This paper presents a comprehensive review of the events that led to the characterization of COX-2 in pre-ovulatory follicles, updates current concepts on the control of COX-2 expression in pre-ovulatory follicles, and addresses the consequences of COX-2 inhibition to women fertility and potential implications of COX-2 expression in ovarian cancer.

The aim of this study was to investigate whether inhibin A and/or activin A play a role in the acquisition of oocyte competence during the final stages of oogenesis. The particular goal was to establish whether inhibin A and activin A exert development-enhancing effects during in vitro maturation in serum-free media and whether such effects are related to changes in the kinetics of meiotic resumption and/or fertilization rates. Cumulus-oocyte-complexes (COCs) were matured in two control media (Medium 199 [M199] with hormones and serum, hormone-serum control; M199 + 0.6% BSA, BSA-control) and nine treatment media (M199 with 0.6% BSA containing 100, 10, and 1 ng/ml of recombinant human inhibin A, recombinant human activin A, and the combination of the two). Oocytes were fertilized and cultured using standard procedures. Cleavage was assessed at 54 h and blastocyst development at 8 days after in vitro fertilization. Kinetics of oocyte maturation and the fertilization rates were evaluated after fixing and staining (Hoechst 33342) of oocytes at 8, 16, and 22 h after onset of in vitro maturation or of presumptive zygotes at 12 h after in vitro fertilization, respectively. Although there was no effect on cleavage rates, inhibin A and activin A significantly enhanced postcleavage development at concentrations of 10 ng/ml (57.7 +/- 7.5% and 56.6 +/- 11.7%, respectively) and 100 ng/ml (50.6 +/- 18.6% and 56.4 +/- 4.0%, respectively) compared to that in the BSA-control group (24.6 +/- 3.2%). Whereas inhibin A- and activin A-treated oocytes showed development-enhancing effects similar to those in the hormone-serum controls, these groups differed with regard to the kinetics of meiotic resumption. Likewise, the enhanced development of the hormone-serum control and the inhibin A/activin A-treated oocytes was not related to increased fertilization rates relative to the BSA-control. These results suggest that inhibin A and activin A may play important roles during the final stages of oogenesis and that recombinant inhibins and activins are useful compounds for the development of a serum-free culture system for in vitro maturation of oocytes from cattle and possibly other mammalian species.

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In contrast to other species, the preovulatory rise in gonadotropins in mares causes a remarkable expansion of the entire granulosa cell layer in vivo, suggesting that hyaluronan (HA) synthesis may be regulated in mural granulosa cells in this species. The objectives of this study were to clone and characterize equine hyaluronan synthase 2 (HAS2) and investigate the regulation of its transcript and of HA synthesis in equine follicles during human chorionic gonadotropin (hCG)- induced ovulation. Results showed that the equine HAS2 cDNA contains a 5'-untranslated region of 436 bp, an open reading frame of 1659 bp, and a 3'-untranslated region of 707 bp. The open reading frame encodes a 552-amino acid protein that is highly conserved (98-99% identity), compared with other known mammalian homologs. The regulation of HAS2 mRNA was studied in equine follicles isolated during estrus between 0 and 39 h after an ovulatory dose of hCG and in corpora lutea obtained on d 8 of the estrous cycle. Results from semiquantitative RT-PCR/Southern blotting analyses revealed a transient induction of HAS2 during the ovulatory process. Levels of HAS2 transcripts were undetectable in follicles before hCG treatment (0 h), increased markedly after gonadotropin treatment (P < 0.05), but returned to undetectable levels in corpora lutea. Analyses performed on isolated preparations of theca interna and granulosa cells showed that the granulosa cell layer was the predominant site of HAS2 expression. An immunohistochemical approach showed that this induction of HAS2 transcript was accompanied by a dramatic increase in HA production after hCG treatment. The isolation and characterization of a 1.8-kb fragment of genomic sequence located immediately upstream of equine HAS2, and comparison with corresponding human and mouse genomic regions identified several conserved putative cis-acting elements. Thus, this study describes the primary structure of equine HAS2, demonstrates for the first time the regulation of HAS2 in mural granulosa cells during the ovulatory process in vivo and identifies a valuable model in which to study the molecular control of HAS2 gene expression.

Summary Endocrine changes in cattle treated with GnRH I. GnRH‐stimulated LH and FSH secretion in relation to stage of cycle and in cows with ovarian cysts The aim of the present investigation was to determine whether there is a difference between LH and FSH secretion in cows with ovarian cyst disease and normal cows stimulated by GnRH. Seven cows were treated with 20 μg GnRH (Buserelin) once in oestrus and on days 3, 13 and 19 of the oestrous cycle. Eighteen cows with ovarian cysts were divided into 2 groups according to a plasma progesterone concentration of greater or lower than 1 ng/ml. These cows, also, were treated with 20 μg Buserelin. The basal LH concentrations in the cyclic cows and in the animals with ovarian cysts were identical. The basal FSH secretion of the cows with ovarian cysts was 25 % lower than in the cyclic animals. The LH secretion released by GnRH of the “cystic” cows was twice that of cows in oestrus and on day 3 of the oestrous cycle. The FSH secretion induced by GnRH in the “cystic” cows with progesterone concentrations below 1 ng/ml were 40 % lower than that of the animals of all other cyclic stages. These differences in the endocrine functions open new aspects for the clinical assessment of ovarian cysts in the cow. Zusammenfassung Es wurde untersucht, ob sich die GnRH‐stimulierte LH‐ und FSH‐Sekretion von Kühen mit Ovarialzysten von derjenigen zyklischer Tiere unterscheidet. In aufeinanderfolgenden Zyklen wurden 7 Kühe der Deutschen Fleckviehrasse je einmal im Oestrus sowie am 3., 13. und 19. Zyklustag mit 20 μg des GnRH‐Analogons Buserelin behandelt. Blutproben zur Bestimmung von LH und FSH wurden vor der Injektion und danach bis zur 7. Stunde in stündlichen Abständen entnommen. Von 18 Kühen, die Ovarzysten mit einem Durchmesser von mindestens 2,5 Zentimeter aufwiesen, wurden auf Grund der Blutplasmaprogesteronkonzentrationen größer bzw. kleiner als 1 ng/ml Blutplasma 2 Gruppen gebildet. Diese Kühe wurden ebenfalls mit 20 μg Buserelin behandelt. Die basalen LH‐Konzentrationen der zyklischen und der an Ovarzysten erkrankten Kühe unterschieden sich nicht, während die basale FSH‐Konzentration der “Zystenkühe” 25% niedriger als die der zyklischen Tiere war (P < 0,05). Die GnRH‐stimulierte LH‐Sekretion der “Zystenkühe” war doppelt so hoch wie diejenige von Kühen im Oestrus und am 3. Zyklustag, während die GnRH‐stimulierte FSH‐Sekretion der “Zystenkühe” mit Progesteronkonzentrationen unter 1 ng/ml Plasma 40 % niedriger war als die der übrigen Tiere an allen Zyklustagen (P < 0,05 bzw. 0,01). Die endokrinen Funktionsunterschiede von “Zystenkühen” im Vergleich zu zyklischen Tieren bieten neue Ansätze für die klinischen Aspekte von Ovarialzystcn beim Rind.