Ovarian response and FSH profile in cows following injection of various doses of inhibin antiserum

Superovulation with an anti-inhibin monoclonal antibody improves the reproductive performance of rat strains by increasing the pregnancy rate and the litter size

Rats are multiparous rodents that have been used extensively in research; however, the low reproductive performance of some rat strains hampers the broader use of rats as a biomedical model. In this study, the possibility of increasing the litter size after natural mating in rats through superovulation using an anti-inhibin monoclonal antibody (AIMA) was examined. In outbred Wistar rats, AIMA increased the number of ovulated oocytes by 1.3-fold. AIMA did not affect fertilization and subsequent embryonic development, resulting in a 1.4-fold increase in litter size and a high pregnancy rate (86%). In contrast, conventional superovulation by eCG/hCG administration decreased the pregnancy rate to 6-40% and did not increase the litter size. In inbred Brown Norway rats, AIMA increased the litter size by 1.2-fold, and the pregnancy rate increased more than twice (86% versus 38% in controls). AIMA also increased the litter size by 1.5-fold in inbred Tokai High Avoiders and Fischer 344 rats. AIMA increased the efficiency of offspring production by 1.5-, 2.7-, 1.4-, and 1.4-fold, respectively, in the four rat strains. Thus, AIMA may consistently improve the reproductive performance through natural mating in rats, which could promote the use of AIMA in biomedical research.

A combined treatment with progesterone, anti-inhibin serum, and equine chorionic gonadotropin improves number of ovulated oocytes in young C57BL/6J mice

Superovulation procedures are routinely and widely used in mouse reproductive technology. Previous studies have shown that a large number of oocytes can be obtained from adult mice (> 10 weeks old) using a combined treatment with progesterone (P4) and anti-inhibin serum (AIS). However, these effects have not been fully investigated in young (4 weeks) C57BL/6J mice. Here, we found that a modified superovulation protocol (combined treatment with P4, AIS, eCG (equine chorionic gonadotropin), and hCG (human chorionic gonadotropin); P4D2-Ae-h) improved the number of oocytes compared to the control (eCG and hCG) (39.7 vs. 21.3 oocytes/mouse). After in vitro fertilization, pronuclear formation rates were 69.3% (P4D2-Ae-h group) and 66.2% (control group). After embryo transfer, 46.4% (116/250) of the embryos in the P4D2-Ae-h group successfully developed to term, which was comparable to the control group (42.9%; 123/287 embryos). In conclusion, our protocol (P4D2-Ae-h) was effective for superovulation in young C57BL/6J mice.

Use of anti-inhibin monoclonal antibody for increasing the litter size of mouse strains and its application to i-GONAD

The litter size of mouse strains is determined by the number of oocytes naturally ovulated. Many attempts have been made to increase litter sizes by conventional superovulation regimens (e.g., using equine or human gonadotropins, eCG/hCG but had limited success because of unexpected decreases in the numbers of embryos surviving to term. Here, we examined whether rat-derived anti-inhibin monoclonal antibodies (AIMAs) could be used for this purpose. When C57BL/6 female mice were treated with an AIMA and mated, the number of healthy offspring per mouse increased by 1.4-fold (11.9 vs. 8.6 in controls). By contrast, treatment with eCG/hCG or anti-inhibin serum resulted in fewer offspring than in nontreated controls. The overall efficiency of production based on all females treated (including nonpregnant ones) was improved 2.4 times with AIMA compared with nontreated controls. The AIMA treatment was also effective in ICR mice, increasing the litter size from 15.3 to 21.2 pups. We then applied this technique to an in vivo genome-editing method (improved genome-editing via oviductal nucleic acid delivery, i-GONAD) to produce C57BL/6 mice deficient for tyrosinase. The mean litter size following i-GONAD increased from 4.8 to 7.3 after the AIMA treatment and genetic modifications were confirmed in 80/88 (91%) of the offspring. Thus, AIMA treatment is a promising method for increasing the litter size of mice and may be applied for the easy proliferation of mouse colonies as well as in vivo genetic manipulation, especially when the mouse strains are sensitive to handling.

Changes in the ovary and the peripheral concentrations of sex hormones after the aspiration of follicular fluid from the spontaneous follicular cysts of dairy cows

The aim of the present study was to clarify the ovarian and hormonal dynamics after the aspiration of follicular fluid in cows with follicular cysts. Follicular fluid was aspirated from the follicular cysts and follicles that were fated to become cystic follicles and other coexisting normal follicles, respectively, in lactating cows (n = 3). After the aspiration procedure, new follicles developed and reached a diameter of 25 mm without ovulation within 13–19 days. The plasma concentrations of inhibin decreased and follicle-stimulating hormone increased rapidly after the aspiration procedure, and subsequently increased and decreased, respectively, as a new follicle grew. No luteal structures developed after the aspiration procedure, and the animals’ plasma progesterone levels remained low. The present study indicates that the cystic follicles are never luteinized by the aspiration of follicular fluid, and consequently, new follicular cysts are observed to repeatedly develop.

The stimulatory effect of subluteal progesterone environment on the superovulatory response of passive immunization against inhibin in goats

The objective of the current study was to investigate the effect of subluteal progesterone environment on the efficacy of the ovarian responses in goats passively immunized against endogenous inhibin. Twelve cycling female Shiba goats were synchronized using two doses of prostaglandin F2α 11 days apart. After detection of ovulation (D0, by ultrasonography), goats were randomly assigned into 2 groups: (1) Subluteal P4 group (SLP; n = 6), treated with a previously once-used controlled intravaginal progesterone-releasing device (ou-CIDR) intravaginal from D 6 to D 12 concurrently with a luteolytic dose of PGF2α at D6 (2) Normal Luteal P4 group (NLP; n = 6), had neither ou-CIDR nor PGF2α. In both groups, goats were treated with an intravenous injection of 10 ml of inhibin antiserum at D10. After that, another luteolytic dose of PGF2α was administrated to goats in both groups at D12, and withdrawal of ou-CIDR in the SLP group. Detection of estrous behavior was checked again 24 h following PGF2α administration and or ou-CIDR withdrawal at 8 h intervals with a teaser buck. The follicle populations ≥4 mm in each goat were monitored through transrectal ultrasonography daily from 1 day after inhibin antiserum administration (0 h) and continued until ovulation had been detected (disappearance of large dominant follicles by ultrasonography). In addition, a repeated ultrasonographic scanning was performed 7 days after ovulation, and the ovulation rate had been estimated by counting the number of observed corpora lutea by ultrasonography. Blood samples were collected for measurement of plasma circulating inhibin binding activity, FSH, LH, estradiol (E2), and progesterone (P4) in both groups. Results revealed significant increases in maximum diameter of the preovulatory follicles (5.92 ± 0.17 mm vs 5.31 ± 0.26 mm; P < 0.05), and the mean maximum number of follicles ≥ 4 mm in diameter (18.45 ± 3.40 vs 12.15 ± 6.21; P < 0.05) in the SLP group compared with that of the NPL group. No significant differences were observed between both groups in term of inhibin binding activity %, and FSH. Following immunization, significant increases in the concentrations of circulating LH (at 72 h) and E2 (from 48 to 84 h) were noted in the SLP group as compared with the values obtained from the goats in the NLP group. Moreover, significant increases in ovulation rate (13.85 ± 1.40 vs 5.67 ± 2.10; P < 0.01) and subsequent P4 concentrations (from 192 to 288 h) were found in the SLP group as against those of the NLP group. In conclusion, maintaining a subluteal P4 environment concurrently with passive immunization against endogenous inhibin may improve the superovulatory response in female Shiba goats.

Superovulation using the combined administration of inhibin antiserum and equine chorionic gonadotropin increases the number of ovulated oocytes in C57BL/6 female mice

Superovulation is a reproductive technique generally used to produce genetically engineered mice. Superovulation in mice involves the administration of equine chorionic gonadotropin (eCG) to promote follicle growth and then that of human chorionic gonadotropin (hCG) to induce ovulation. Previously, some published studies reported that inhibin antiserum (IAS) increased the number of ovulated oocytes in ddY and wild-derived strains of mice. However, the effect of IAS on the C57BL/6 strain, which is the most widely used inbred strain for the production of genetically engineered mice, has not been investigated. In addition, the combined effect of IAS and eCG (IASe) on the number of ovulated oocytes in superovulation treatment has not been examined. In this study, we examined the effect of IAS and eCG on the number of ovulated oocytes in immature female mice of the C57BL/6 strain in superovulation treatment. Furthermore, we evaluated the quality of obtained oocytes produced by superovulation using IASe by in vitro fertilization (IVF) with sperm from C57BL/6 or genetically engineered mice. The developmental ability of fresh or cryopreserved embryos was examined by embryo transfer. The administration of IAS or eCG had a similar effect on the number of ovulated oocytes in C57BL/6 female mice. The number of ovulated oocytes increased to about 3-fold by the administration of IASe than by the administration of IAS or eCG alone. Oocytes derived from superovulation using IASe normally developed into 2-cell embryos by IVF using sperm from C57BL/6 mice. Fresh or cryopreserved 2-cell embryos produced by IVF between oocytes of C57BL/6 mice and sperm from genetically engineered mice normally developed into live pups following embryo transfer. In summary, a novel technique of superovulation using IASe is extremely useful for producing a great number of oocytes and offspring from genetically engineered mice.

Changes in circulatory FSH of Barbari goats following treatment with high molecular weight inhibin isolated from buffalo follicular fluid

The objective of the present study was to isolate and purify high MW inhibin (≈ 129 kDa) from buffalo ovarian follicular fluid (buFF) and to investigate its biological activity. Throughout the process of purification, the inhibin fractions were evaluated for bioactivity by a specific, sensitive and uniformly reproducible bioassay in mice. The final biological activity of this preparation was tested in normal cycling adult female Barbari goats. Eight animals, randomly divided into two groups, were synchronized for estrus by administering PGF2α twice at an interval of ten days. Following synchronization, the treatment group (n=4) received (i.m.) 0.4 ml (240 μg protein total dose) of purified inhibin (MW ≈ 129 kDa) of buFF in the morning at 08.00 h for the four consecutive days of follicular phase, while the control group (n=4) received only saline (0.4 ml). Blood samples were collected from jugular vein immediately before the first injection and subsequent collections were made daily in the afternoon until day 8 of the experiment including four days (0, 1, 2, & 3 days) of the next cycle. FSH was assayed in all the samples by ELISA. The peripheral FSH concentration sharply declined from 1.854±0.137 to 0.979 ± 0.02 u/l, 8h after the administration of inhibin on the first day. The value in controls was 2.004 ± 0.132 u/l. For the duration of treatment of four consecutive days, the FSH level in experimental group remained significantly low (p<0.05) compared to control group. After cessation of treatment, the FSH level remained low on day 0 and 1 of the next cycle in the experimental and control animals. However, a significant rebound increase in plasma FSH levels occurred on day 2 & 3 (2.73 ± 0.179 & 1.849 ± 0.128 u/l) only in the experimental group compared to control animals (P<0.05). This increment might be caused by the rebound surge of FSH from anterior pituitary which further corroborates the effect of inhibin in treated animals. In conclusion, the present study demonstrates that the high MW form of inhibin (≈ 129 kDa) isolated from buFF has comparable biological activity as revealed by 31-32 kDa inhibin from other species.

An MspI polymorphism in the inhibin alpha gene and its associations with superovulation traits in Chinese Holstein cows

To identify a predictor to forecast superovulation response on the basis of associations between superovulation performance and gene polymorphism, the PCR-RFLP method was applied to detect an A>G transition determining an MspI polymorphism at position 192 in the exon I of the bovine inhibin alpha (INHA) gene and evaluate its associations with superovulatory response in 118 Chinese Holstein cows treated for superovulation. Association analysis showed that cows with the GG genotype resulted in a significant increase in the number of ova (TNO) than AG and AA genotypes in the first (P=0.023), second (P=0.004) and third (P=0.002) superovulation treatments and produced more transferable embryos (NTE) than that of AG and AA genotypes in the third (P=0.045) superovulation treatment. Moreover, individuals with GG genotype produced more transferable embryos than AA (P<0.05) genotype in the second superovulation treatment and all cows without superovulation response were mutations with genotypes of AA and AG. These results indicate that INHA gene can be used as a predictor for superovulation in Chinese Holstein cows, and imply that cows with AA genotype should be excluded for superovulation practices.

Development and evaluation of a novel DNA vaccine expressing inhibin alpha (1-32) fragment for improving the fertility in rats and sheep

Inhibin is an important protein hormone in regulating folliculogenesis. Immunization against inhibin can improve follicle developments. The objective of present study is to investigate inhibin DNA immunization as a potential tool for improving follicle development and litter sizes of female animals. In our study, the inhibin DNA vaccine was constructed with inhibin alpha (1-32) fragment inserted into the C termination of HBsAg-S. Ninety rats and forty sheep were immunized with inhibin DNA vaccine. In rats, immunization against inhibin resulted in increase of positive sera ratio (P<0.01). The treatment was accompanied by a significant increase in the total number of mature follicles of >0.8mm in diameter on the onset of estrous cycle after twice immunization (31.0+/-3.9 in the test groups versus 27.4+/-5 in control groups) and after third immunization (35.2+/-6.7 in the test groups versus 30.3+/-5.2 in control groups). Litter sizes were significantly (P<0.05) bigger in rats treated with inhibin DNA vaccine (12.7+/-4.5 n=6) than in control (9.8+/-4.5). In sheep, twinning rate in test groups (39.2%) was significantly higher than that in control groups (10%) after immunization (P<0.05). These results indicated that inhibin was an important factor in improvement of fertility in rats and sheep, and demonstrated that DNA immunization against inhibin could induce more mature follicles resulting in increased litter sizes. Our results revealed that inhibin DNA vaccine may be an alternative to the use of exogenous gonadotrophins for increasing ovarian follicular development and improving animal fertility.

Immunization of Goats against Inhibin Increased Follicular Development and Ovulation Rate

In the present study, two experiments were conducted to induce superovulation in goats using passive and active immunization against inhibin. In the first experiment, two groups of goats were given an intravenous injection of either 10 ml normal goat serum (control; n=6) or inhibin antiserum developed against [Tyro30]-inhibin alpha (1-30) (passively immunized; n=6) 48 h before treatment with PGF2alpha. In the second experiment, two groups of goats were immunized with inhibin vaccine (actively immunized; n=5) or Freund's adjuvant (control; n=5) followed by three booster immunizations at 4 week intervals. Blood samples were collected for determination of FSH, LH, estradiol-17beta, and progesterone. Ultrasonography was used to determine ovarian activity at PGF2alpha injection and ovulation rate one week after estrus. In both experiments, there was a significant increase in plasma FSH concentration compared with the controls. However, the pattern of the FSH levels was different between the passively and actively immunized goats. The numbers of follicles in passively and actively immunized goats (22.4 +/- 2.3 and 18.6 +/- 2.1, respectively) were significantly greater than those in the controls (2.6 +/- 0.4 and 2.3 +/- 0.4, respectively). In addition, the ovulation rate was greater in the immunized animals compared with the controls. Therefore, either passive or active immunization against inhibin could be used to induce superovulation in goats.

Reproductive Hormones and Follicular Growth During Development of One or Multiple Dominant Follicles in Cattle1

The mechanisms regulating ovulation rate under natural conditions are not yet defined, particularly for monovular species. In the present study, we evaluated ovarian structures (every 12 h by ultrasonography) and circulating hormones (every 6 h) to determine the differences between cows that developed one (single dominant; n = 16), two (double dominant; n = 8), or three (triple dominant; n = 3) dominant follicles. The four largest follicles were tracked retrospectively, and the data were normalized to the time of expected follicular deviation (F1 >/= 8.5 mm; hour 0). Follicular dynamics from emergence to deviation were similar, whereas after deviation, expected subordinate follicles continued to grow at a rate similar to the dominant follicle. Triple dominants had greater FSH than double dominants (hour -24 to hour -12) and single dominants (hour -42 to hour -6), and double dominants had greater FSH than single dominants (hour -24 to hour -12). Increased circulating estradiol but lower inhibin were observed in cows that developed multiple follicles. In addition, double dominants had greater LH than single dominants (hour -42 to hour -24 and hour -6 to hour 0) and lower progesterone than single dominants (hour -12 and hour -6). Luteal volume was similar between groups, but milk production was greater for codominant than for single-dominant cows. Thus, selection of multiple dominant follicles during high milk production is related to a transient increase in circulating FSH and LH during the 24 h before follicular selection, producing continued postdeviation growth of follicles that ordinarily would have regressed. Increased FSH and LH probably result from decreased circulating inhibin and progesterone in cows that develop codominant follicles.

Active immunization against inhibin improves superovulatory response to exogenous FSH in cattle

The effect of active immunization against inhibin on the response to superovulatory treatment by porcine FSH (pFSH) was investigated in cattle. Japanese black cows were sc injected with 1 mg of porcine inhibin alpha-subunit fragment (1-26) conjugated with rabbit serum albumin (inhibin-immunized group; n=14) or rabbit serum albumin alone (control group; n=12) in Freund's complete adjuvant. Booster injections (half the amount of the primary injection) were given 35 and 70 days after the primary injection. All cows were superovulated three times with pFSH. Three days after each injection of the antigen, a progesterone-releasing intravaginal device (CIDR-B) was inserted vaginally into all animals and left in place for 10 days. Forty-eight hours before CIDR-B removal, all animals were sc injected with 30 mg pFSH dissolved in 40% polyvinylpyrrolidone, and im injected with 750 microg of PGF2alpha at CIDR-B removal. Cows were artificially inseminated twice during estrus, and ova or embryos were collected 7 or 8 days after estrus. The number of corpora lutea, the number of ova or embryos and the number of transferable embryos in inhibin-immunized cows (12.1+/-1.2, 11.1+/-1.3 and 6.2+/-1.0, respectively) were significantly greater than those in the controls (8.2+/-1.0, 5.7+/-1.1 and 3.1+/-0.7, respectively). These results indicate that active immunization against inhibin enhanced ovarian response to the usual superovulatory treatment in cattle. Therefore, immunization against inhibin may be a useful approach for improving the response to superovulation in cattle.

Plasma concentrations of inhibin A in cattle with follicular cysts: relationships with turnover of follicular waves and plasma levels of gonadotropins and steroid hormones

We investigated the profiles of circulating levels of inhibin A and total inhibin in beef cows with follicular cysts in relation to the patterns of follicular development and circulating gonadotropins and steroid hormones. Turnover of follicular waves was monitored in five cows every 2 days for 70 days from 10 days after detection of estrus without ovulation. The mean interwave intervals were 19.6 +/- 1.0 days (n = 18 waves with cysts from the five cows). Circulating levels of inhibin A were approximately 170 pg/ml before emergence of follicular waves with cysts and increased (P < 0.05) concomitantly with follicle emergence. High concentrations of inhibin A (greater than 300 pg/ml) were noted for 7 days during the growth phase of cystic follicles, but inhibin A levels decreased gradually when development of the cysts reached a plateau. This profile of inhibin A was similar to those of total inhibin and estradiol, but was inversely related to the changes in plasma FSH concentrations. LH pulse frequency and mean concentrations of LH in cows with cysts were higher than those observed in the luteal phase of normal cyclic cows. These results indicate that the capacity to secrete inhibin, as well as estradiol, is maintained in cystic follicles, the growth of which is extended by LH secretion at levels greater than those seen in the normal luteal phase. Inhibin A plays an important role in the extension of interwave intervals by suppressing recruitment of a new cohort of follicles.

Effects of re-immunization of heifers against inhibin on hormonal profiles and ovulation rate

To study the effect of re-immunization against inhibin on ovarian response and hormonal profiles, Japanese beef heifers (n = 5) were re-immunized three times with inhibin vaccine (recombinant ovine inhibin α-subunit in oil emulsion, 125 μg ml−1) one year after the primary immunization. Control heifers (n = 5) were injected with placebo (Montanide: Marcol adjuvant alone). Oestrous cycles were synchronized by using prostaglandin F2α (PGF2α) and ovarian response was monitored daily by ultrasonography. Blood samples were collected by jugular venipuncture for assessment of hormonal levels and inhibin antibody titres. In contrast to controls, inhibin re-immunized heifers generated antibodies against inhibin rapidly reaching a peak level 9 days after the first booster injection. The mean concentrations of FSH in re-immunized cows increased significantly in comparison with controls. In addition, there was a significant increase in oestradiol-17β and progesterone levels in re-immunized cows compared with controls. Inhibin re-immunized heifers had a significant increase in small (≥4 < 7 mm), medium (≥7 < 10 mm) and large (≥10 mm in diameter) sized follicles. Moreover, the mean ovulation rate was 5.0 ± 1.1 after the third booster injection in re-immunized heifers compared with control heifers (single ovulation). These results clearly demonstrate that re-immunization of inhibin can be used to enhance ovarian follicular development and ovulation rate. Furthermore, the great number of follicles is a potential source of oocytes that could be harvested for in vitro fertilization and embryo transfer programmes.

A new alternative method for superovulation using passive immunization against inhibin in adult rats

The present study was undertaken to investigate the effects of passive immunoneutralization of endogenous inhibin on ovulation rate and embryo development in vivo and in vitro to establish a new alternative superovulation method in the adult rat. Female adult rats of Wistar strain were superovulated with a single injection of inhibin antiserum (inhibin-AS; 100 or 400 microl) or an injection of 20 IU eCG followed by an injection of 10 IU hCG. Untreated animals served as controls. Embryos were collected from oviducts or uteri on Days 1-5 of pregnancy, and the number of embryos and implantation sites were observed. On Day 1 of pregnancy, the two-cell-stage embryos were cultured and embryos from the 100-microl inhibin-AS group and the control group were transferred to recipient females to determine developmental competence. There were no significant differences between groups in fertilization rate. The numbers of normal embryos in the inhibin-AS-treated groups were significantly higher than the control and the eCG-hCG-treated groups throughout Days 1-4 of pregnancy. The number of implantation sites observed on Day 5 of pregnancy in the inhibin-AS-treated groups was significantly higher than both the control and the eCG-hCG-treated groups. Furthermore, the rate of blastocyst development in vitro in the inhibin-AS-treated groups and posttransfer viability in the 100-microl-inhibin-AS group were comparable with those of the control group. These results indicate that immunoneutralization of endogenous inhibin is a new practical alternative for induction of superovulation as a substitution for eCG-hCG method in the adult rat.

Passive Immunoneutralization of Endogenous Inhibin Increases Ovulation Rate in Miniature Shiba Goats

We reported previously that passive immunization against inhibin enhances follicular growth and increases the ovulation rate. However, the ovulation rate was not comparable to the number of follicles. Therefore, the aim of this study was to attempt to increase the ovulation rate by increasing the interval between inhibin immunization and PGF2alpha injection. Five miniature Shiba goats were treated with 10 ml inhibin antiserum (inhibin-AS) developed against [Tyro30]-inhibin alpha (1-30). A control group (n=5) was treated with normal goat serum. All animals were injected intramuscularly with 125 microg PGF2alpha 72 h after treatment to induce estrus and ovulation. Blood samples were collected for hormonal assay and the ovulation rate was determined by laparotomy. In contrast to the control group, there was a significant increase in plasma concentrations of FSH in the immunized group. After luteolysis, plasma concentrations of estradiol-17beta increased markedly to a preovulatory peak about 2 folds higher (P<0.01) than that of controls. In addition, the ovulation rate was greater in the immunized group (14.4 +/- 2.2) than in the control group (2.2 +/- 0.6), and the mean number of follicles > or = 4 mm in diameter was 10.0 +/- 0.8 in the inhibin-AS group compared with 2.4 +/- 0.3 in control group. The present results demonstrate that immunoneutralization of endogenous inhibin increased FSH secretions in miniature shiba goats. The increased FSH secretion enhanced follicular growth and increased the ovulation rate. Additionally, increasing the interval between inhibin-AS and PGF2alpha injections (to 72 h) resulted in a greater ovulation rate compared with the previous protocol (48 h). Therefore, inhibin-AS treatment proved to be an effective alternative to exogenous gonadotropin methods for induction of superovulation in goats.

A Direct Time-Resolved Fluoroimmunoassay (TR-FIA) for Measuring Plasma Estradiol-17.BETA. Concentrations in Cattle

A direct Time-Resolved Fluoroimmunoassay (TR-FIA) system for measuring estradiol-17beta (E(2)) in bovine plasma was developed and evaluated. A 100 microl sample of bovine plasma was used for a TR-FIA without prior extraction and purification. The dose-response curves of reference standards ranged from 0.0625 to 10 pg/well. The minimum detectable concentration of this assay system was 0.625 pg/ml, and 19 pg/ml of E(2) caused a 50% reduction of maximum binding. The intra- and inter-assay coefficients of variation were 10.2 and 17.4%, respectively. The plasma E(2) concentrations measured by direct TR-FIA correlated closely with those measured after extraction (r=0.939). The results in the present study indicate that the TR-FIA reagent for E(2), designed for human research can also be utilized, with some modification, for direct assaying in bovine plasma. This assay type seems to fulfill the requirements for safety, sensitivity, specificity, reproducibility and practical convenience.

Dizygotic twinning is not linked to variation at the alpha-inhibin locus on human chromosome 2

Natural multiple pregnancy in women leading to dizygotic (DZ) twins is familial and varies across racial groups, suggesting a genetic predisposition. Mothers of DZ twins have a higher incidence of spontaneous multiple ovulation and elevated FSH concentrations. FSH release is controlled by feedback of inhibin peptides from the ovary, and immunization against inhibin alpha-subunit results in an increased ovulation rate in animals. The inhibin alpha-subunit is therefore a candidate gene for mutations that may increase the frequency of DZ twinning. Restriction digests of a PCR product from exon 1 with the enzyme SpeI detects a C/T polymorphism at bp 128 with two alleles of 447 and 323/124 bp. The polymorphism was typed in 1,125 individuals from 326 pedigrees with 717 mothers of spontaneous DZ twins. The alpha-inhibin locus mapped within 3 centimorgans of D2S164, and linkage with DZ twinning was excluded [decimal log odds ratio (LOD) score, -2.81 at theta = 0]. There was complete exclusion of linkage (LOD, less than -2) of a gene conferring relative risk 1.8 (lambdas, >1.8) across the chromosome, except at the p-terminus region and a small peak (maximum LOD score, 0.6) in the region of D2S151-D2S326. Analysis using either recessive or dominant models excluded linkage with DZ twinning in this population (LOD score, less than -2.5) across chromosome 2. We conclude that dizygotic twinning is not linked to variation in the alpha-inhibin locus. The results also suggest that mutations in other candidates on chromosome 2, including the receptor for FSH and the betaB-inhibin subunit (INHBB) cannot be major contributors to risk for DZ twinning.