The ovary

Intra-follicular activin availability is altered in prenatally-androgenized lambs

Prenatal exposure of sheep to testosterone (T) disrupts ovarian cyclicity and leads to anovulation in adulthood. We propose that the disruption of ovarian function in prenatally-androgenized sheep is mediated via follicular defects stemming from reduced intrafollicular activin availability/action. The intra-follicular activin availability/action that facilitates follicular development is dictated by the relative proportions of activins, inhibins (antagonists of activin action) and follistatins (FS; binding proteins of activin and negator of activin action). Inhibin alpha, beta A, beta B, and FS mRNA expression were determined by in situ hybridization in 5 week-old ovaries from control (C) lambs or those exposed to testosterone (T) or DHT from 30-90 days of gestation. In utero exposure to T, but not DHT, increased total ovarian weight (0.4+/-0.1,1.5+/-0.5 and 0.3+/-0.1 g, C, T and DHT, respectively) and total number of follicles (16.5+/-2.8,37.8+/-7.9, and 18.8+/-3.0). With the exception of two follicles in T animals, all follicles were < or = 2 mm in diameter. All follicles < or = 2 mm in all groups expressed FSH receptor mRNA in the granulosa cells and LH receptor only in the thecal cells. The percentage of follicles expressing FS mRNA was increased (P<0.05) in sheep prenatally-androgenized with either T (80.4+/-8) or DHT (80.3+/-5.5) as compared to C (50.8+/-8.2). In contrast, the percentage of follicles expressing activin beta B mRNA tended to be lower (P=0.06) in the T (30.9+/-7.1) and DHT (40.5+/-3.3) groups as compared to C (66.1+/-15.6). Increased expression of FS along with the reduced expression of activin beta B mRNA provides evidence for compromised intra-follicular activin availability in the majority of follicles in the androgenized groups. The increase in ovarian weight and follicular number in the T, but not in the DHT group, suggests that the effects of T are mediated through the action of estrogen. We speculate that the decrease in relative abundance of activin may contribute to the selection defects in prenatally-androgenized sheep. If true, this may be a useful model to understand the etiology of polycystic ovarian syndrome.

Insulin-like growth factor binding protein-3 reduction in follicular fluid in spontaneous and stimulated cycles

OBJECTIVE

To investigate serum and follicular fluid insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) behavior in spontaneous and in superstimulated cycles.

DESIGN

Estradiol, GH, IGF-I, and IGFBP-3 were evaluated in serum and in follicular fluid during spontaneous and stimulated cycles.

SETTING

Department of Obstetrics and Gynecology, University of Naples, Naples, Italy.

PATIENT(S)

Ninety-two patients with regular menstrual cycles and tubal and/or male factor infertility undergoing treatment with an IVF program.

INTERVENTION(S)

The superstimulated IVF program uses leuprolide acetate suppression followed by hMG in a sequential manner in the subsequent cycle. After sufficient follicular development, hCG was administered, followed 34-36 hours later by oocyte retrieval.

MAIN OUTCOME MEASURE(S)

Growth hormone, IGF-I, and IGFBP-3 were assayed by RIA and immunoradiometric assay techniques.

RESULT(S)

Growth hormone levels in serum and in follicular fluid were higher after FSH-stimulated cycles than after physiologic cycles. Serum and follicular fluid IGF-I did not change during physiologic and FSH-stimulated cycles. Serum IGFBP-3 decreased only in FSH-stimulated cycles. Levels of IGFBP-3 in follicular fluid were lower than serum levels in late follicular phase both in physiologic and in FSH-stimulated cycles.

CONCLUSION(S)

Reduction of IGFBP-3 is an important mechanism allowing a larger local availability of free IGFs, which modulate the response of follicles to gonadotropin stimulation. This effect is amplified in stimulated cycles.

A sparsely vascularised zone in the cortex of the bovine ovary

We consider that the microvascular bed may play a role in the initiation and maintenance of growth from primordial to primary follicles. Therefore, using immunochemistry, we examined microvessels in calf and cow ovaries to identify the presence of factor VIII-related antigen endothelial cells. A vessel-poor zone was observed in the cortex of immature and mature cow ovaries. Primordial and primary follicles were assembled in this zone. It is concluded that follicular dormancy is likely to be maintained by the scarcity of microvessels and thus by the consequent poverty of the blood supply.

Effect of sheep and human follicular fluid on the maturation of sheep oocytes in vitro

This study examines the effect of sheep and human follicular fluid on the in vitro maturation (IVM) of sheep follicular oocytes. Oocyte cumulus complexes recovered post mortem were matured for 24 to 26 h at 38.6 degrees C, 5% CO(2) in air, in TCM-199 bicarbonate medium supplemented with 20% fetal calf serum (FCS) and, where stated, with maturation hormones, including FSH (5.0 microg/ml), LH (5.0 microg/ml) and estradiol (1 microg/ml), or with sheep follicular fluid recovered from large (>5 mm) or small (2 to 5 mm) ovarian follicles post mortem, or with human periovular follicular fluid obtained during routine IVF procedures. The matured oocytes were then denuded, and their maturation stage and developmental capacity were assessed by in vitro fertilization (IVF) and culture (IVC). It was found that inclusion of sheep or human follicular fluid or hormone supplements in the IVM media more than doubled the number of oocytes completing maturation (FCS alone 33%, compared with 76.2% for maturation hormones, 84.2% for fluid from large and 69.6% for fluid from small sheep follicles and 82.6% for human follicular fluid), and significantly increased fertilization rates (FCS alone 51.6%, compared with 71.9% for maturation hormones, 78.4% for fluid from the large and 75.7% for fluid from small sheep follicles and 73.1% for human follicular fluid) without discernible adverse effects on the development of the cleaving embryos to the morula or blastocyst stage in culture. Omission of FCS and supplements from the IVM medium resulted in a marked reduction (56%) in the number of oocytes maturing. This reduction could be offset to a large part, but not completely, by inclusion of human follicular fluid or human follicular fluid plus LH (5 microg/ml) in the medium. The results of this study show that addition of sheep or human follicular fluid to maturation medium can enhance rather than inhibit the maturation and fertilizability of sheep follicular oocytes in vitro.