Injection Of Gonadotrophin-releasing Hormone Agonist Research Articles

Effects of GnRHa on early embryonic development in mice receiving cyclophosphamide.

There is a controversy whether GnRH agonist can reduce the deleterious effects of chemotherapy to prevent ovarian failure. We aimed to examine the possible protective effects of a gonadotrophin-releasing hormone agonist (GnRHa) on the fertilization rate and sequential embryonic development in mouse oocytes exposed to Cy. Mice were assigned to three groups of six animals each. A single dose of 75 mg/kg Cy was given intraperitoneally to the Cy mice group. The subcutaneous GnRHa injection was initiated 1 week before and continued for 1 week after the Cy injection in the GnRHa + Cy group. The animals given cyclophosphamide mated 1 week after the Cy injection. At the end of the injection period, the animals underwent a superovulation regime with pregnant mare serum gonadotrophin and human chorionic gonadotrophin and were mated. Early embryos were collected at 48 h after mating. The control group received only the superovulation regime and then mated. Cyclophosphamide caused a significant decrease in the fertilization rate (p < 0.001), whereas the GnRHa improved the rate when compared to control group. The GnRHa induced a marked increase in the rate for 2-cell embryos compared with the Cy group (p = 0.003). In both Cy-injected groups, the rates for the 4-cell embryos were lower than those of the control animals (p < 0.001). However, this rate was higher in the GnRHa + Cy group than in the only Cy group. Morphologically abnormal embryos showed such characteristics as condensed cytoplasm, milky cytoplasm, fragmentation, and an empty zona pellucida. These results demonstrated that the GnRHa preserved the oocyte capability to develop into an embryo against ovarian toxic chemotherapy. Thus, we suggest that GnRHa cotreatment could increase the number and quality of early embryos in mice.

Dose-dependent effect of a single GnRHa injection on the spawning of meagre (Argyrosomus regius) broodstock reared in captivity

The present study aimed to determine the spawning efficacy, egg quality and quantity of captive breed meagre induced with a single gonadotrophin‐releasing hormone agonist (GnRHa) injection of 0, 1, 5, 10, 15, 20, 25, 30, 40 or 50 µg kg-1 to determine a recommended optimum dose to induce spawning. The doses 10, 15 and 20 μg kg-1 gave eggs with the highest quality (measured as: percentage of viability, floating, fertilisation and hatch) and quantity (measured as: total number of eggs, number of viable eggs, number of floating eggs, number of hatched larvae and number of larvae that reabsorbed the yolk sac). All egg quantity parameters were described by Gaussian regression analysis with R2=0.89 or R2=0.88. The Gaussian regression analysis identified that the optimal dose used was 15 μg kg-1. The regression analysis highlighted that this comprehensive study examined doses that ranged from low doses insufficient to stimulate a high spawning response (significantly lower egg quantities, p&lt;0.05) compared to 15 μg kg-1 through to high doses that stimulated the spawning of significantly lower egg quantities and eggs with significantly lower quality (egg viability). In addition, the latency period (time from hormone application to spawning) decreased with increasing doses to give a regression (R2=0.93) which suggests that higher doses accelerated oocyte development that in turn reduced egg quality and quantity. The identification of an optimal dose for the spawning of meagre, which has high aquaculture potential, represents an important advance for the Mediterranean aquaculture industry.

Effect of pretreatment with insulin on the response of buffaloes with inactive ovaries to gonadotrophin-releasing hormone agonist treatment in summer

The aim of the present study was to evaluate the effect of a pretreatment with insulin on the response of buffalo cows with inactive ovaries to gonadotrophin-releasing hormone agonist (GnRHa) treatment during hot summer months (July and August). Thirty-six Egyptian buffalo cows with inactive ovaries were randomly allocated into three groups: (1) group treated with GnRHa (G1, n = 16) in which each buffalo received an intramuscular injection of 250 mg of GnRHa (Day 0; gonadorelin, Fertagyl); (2) group treated with insulin before the GnRHa injection (G2, n = 8) in which each buffalo received a subcutaneous injection of biphasic insulin at a dose of 0.25 IU kg(-1) bodyweight once daily starting at Day -3 for 3 consecutive days, followed by an intramuscular injection of 250 mg of GnRHa on Day 0; and (3) the control group (G3, n = 12) in which each buffalo cow received an intramuscular injection of 2.5 mL of sterile saline on Day 0. The ovaries of all animals were examined by trans-rectal ultrasonography (5 MHz) on Days -7, -3 and 0 and continued thereafter at 4-day intervals until oestrus or the end of the experiment. On the same days that ultrasound examinations were performed blood samples were collected to measure the progesterone concentrations. Administration of insulin for 3 days before GnRHa injection (G2) significantly (P < 0.05) increased the diameter of the largest follicle from 6.85 +/- 0.64 to 12.4 +/- 0.88 mm. There was a significant (P < 0.01) increase in the oestrous induction rate in G2 compared with both G1 and G3 during the first 12 days after the treatment interval. It is concluded that pretreatment with insulin for 3 days before GnRHa injection increases the diameter of the dominant follicle and therefore the oestrous induction rate of acyclic buffaloes.

Quantification of stem cell factor mRNA levels in the rat testis: usefulness of clusterin mRNA as a marker of the amount of mRNA of sertoli cell origin in post pubertal rats

Spermatogenesis is a complex cellular process regulated by gonadotrophins and local cell-cell interactions. Stem cell factor (SCF) is one of the paracrine factors, produced by the Sertoli cells, involved in the local regulation of spermatogenesis. Measurement of its testicular level is important for addressing its role in testis physiopathology. However, the relative cell composition of experimental and pathological testis samples may lead to misinterpretation in relating SCF mRNA levels to the amount of RNA extracted from the whole tissue sample. Taking into account the relative RNA content of Sertoli cell origin should provide more significant data. In the present study, three sets of experiments were intended for modifying the proportion of RNA of Sertoli cell origin in RNA extracted from whole testis tissue samples: during postnatal development; following methoxy-acetic acid (MAA) administration; and after injecting a long-acting gonadotrophin-releasing hormone agonist (GnRHa). In a first step, we demonstrated clusterin mRNA level stability in purified Sertoli cell preparations between 20 days and adulthood, and following MAA or GnRHa treatment. In a second step, we used a competitive RT-PCR assay to measure SCF and clusterin mRNA levels and expressed the amount of SCF mRNA relative to the amount of clusterin mRNA under the above experimental conditions. The SCF/clusterin mRNA level ratio was found to remain roughly stable from 20 days post-partum to adulthood; i.e. during the development of spermatogenesis. MAA administration led to an overall increase in the SCF/clusterin mRNA level ratio between 7 and 14 days after administration, consistent with the replenishment of the testis with pachytene spermatocytes and round spermatids. Conversely, after long-acting GnRHa injection, the SCF/clusterin mRNA level ratio decreased only slightly from day 21 onward. Hence, the present studies indicate that, under physiopathological conditions, the amount of clusterin mRNA is a good marker of the amount of RNA of Sertoli cell origin in testis samples at day 20 or later; different experimental alterations of spermatogenesis are associated with different patterns of SCF mRNA levels; the relationship between FSH and SCF in vivo is not as simple as that described in vitro.

Use of a single bolus of GnRH agonist triptorelin to trigger ovulation after GnRH antagonist ganirelix treatment in women undergoing ovarian stimulation for assisted reproduction, with special reference to the prevention of ovarian hyperstimulation syndrome: preliminary report: short communication.

A new treatment option for patients undergoing ovarian stimulation is the gonadotrophin-releasing hormone (GnRH) antagonist protocol, with the possibility to trigger a mid-cycle LH surge using a single bolus of GnRH agonist, reducing the risk of developing ovarian hyperstimulation syndrome (OHSS) in high responders and the chance of cycle cancellation. This report describes the use of 0.2 mg triptorelin (Decapeptyl) to trigger ovulation in eight patients who underwent controlled ovarian hyperstimulation with recombinant FSH (rFSH, Puregon) and concomitant treatment with the GnRH antagonist ganirelix (Orgalutran) for the prevention of premature LH surges. All patients were considered to have an increased risk for developing OHSS (at least 20 follicles > or =11 mm and/or serum oestradiol at least 3000 pg/ml). On the day of triggering the LH surge, the mean number of follicles > or =11 mm was 25.1 +/- 4.5 and the median serum oestradiol concentration was 3675 (range 2980-7670) pg/ml. After GnRH agonist injection, endogenous serum LH and FSH surges were observed with median peak values of 219 and 19 IU/l respectively, measured 4 h after injection. The mean number of oocytes obtained was 23.4 +/- 15.4, of which 83% were mature (metaphase II). None of the patients developed any signs or symptoms of OHSS. So far, four clinical pregnancies have been achieved from the embryos obtained during these cycles, including the first birth following this approach. It is concluded that GnRH agonist effectively triggers an endogenous LH surge for final oocyte maturation after ganirelix treatment in stimulated cycles. Our preliminary results suggest that this regimen may prove effective in triggering ovulation and could be said to prevent OHSS in high responders. The efficacy and safety of such new treatment regimen needs to be established in comparative randomized studies.

Effects of chronic treatment with a gonadotrophin-releasing hormone agonist on peripheral concentrations of FSH and LH, and ovarian function in heifers

The effect of chronic treatment with a gonadotrophin-releasing hormone agonist (GnRHa) on ovarian function in cattle was investigated by injecting heifers i.m. twice a day with saline, 5 micrograms GnRHa (Buserelin) or 10 micrograms GnRHa (n = 7) for 21 days. Blood samples were taken twice a day during the treatment period, and then three times a day for 7 days and once daily for a further 4 days. Frequent samples were also collected on day 1, day 10 and day 21 of treatment. The ovaries of all heifers were examined daily using real-time ultrasonography throughout the experimental period. No significant differences in the response were observed between two doses of GnRHa. The first GnRHa injection produced a large LH and FSH surge and this acute response was still present by day 21 of treatment, but both the magnitude and duration of response were significantly attenuated (P < 0.01). After an initial increase, LH returned to the basal concentration, which was maintained until the termination of treatment, when concentrations increased significantly, with a preovulatory surge occurring approximately 6 days later. Peripheral FSH concentrations during the oestrous cycle in control animals displayed a pattern of three waves, each of which closely preceded a wave of follicular development. Concentrations of FSH in GnRHa-treated heifers showed a normal pattern for the first wave after the start of treatment. During the next wave, concentrations increased and remained at the peak values until about 4 days after the end of treatment. An additional ovulation was induced in 11 of 14 GnRHa-treated heifers within 2-3 days of the start of treatment, and a significant (P < 0.05) increase in serum progesterone concentrations was detected 2 days later. All GnRHa-treated heifers then showed a normal follicular wave, with the development and regression of a dominant follicle. The dominant follicles from the next wave grew to only 7-9 mm in diameter and remained at this size until the end of treatment, when they resumed growth, ovulated approximately 7 days later and formed corpora lutea. We conclude that chronic treatment of heifers with GnRHa for 3 weeks suppresses pulsatile secretion of LH and blocks the development of dominant follicles beyond 9 mm in diameter, preventing the preovulatory LH surge and ovulation. However, GnRHa did not suppress the secretion of FSH within the 3 week treatment period. The maintenance of the dominant follicles for an extended period should provide an ideal model to study the control of follicular atresia in cattle in vivo.

Effects of hormonal manipulation on the resumption of postpartum reproductive activity in Texel ewes

Three experiments were conducted on Texel ewes to study the influence of prostaglandin F 2α (PGF 2α), prolactin (PRL), estradiol (E 2), and gonadotrophin releasing hormone (GnRH) on postpartum reproductive activity. In Experiment 1, oral administration of indomethacin (25 to 50 mg/day/ewe) from Day 3 post partum to the first detected estrus inhibited plasma 13, 14-dihydro-15-keto, PGF 2α (PGFM) concentrations (P < 0.0001). This treatment resulted in an earlier rise in the frequency and amplitude of luteinizing hormone (LH) pulses and a resumption of estrous behavior (P < 0.05), while ovarian activity estimated by progesterone (P 4) concentrations resumed to the same extent in treated ewes and controls. Bromocriptine treatment (2.5 mg/day/ewe) reduced plasma PRL levels (P < 0.0001) but had no effect on ovarian activity as evidenced by P 4 and resumption of estrus or on either the frequency or amplitude of the LH pulse. In Experiment 2, a single injection of GnRH agonist (42 mcg of buserelin/ewe) on Day 16 post partum resulted in an abrupt elevation of plasma LH concentrations; mean LH values were 18 to 27 times higher when compared with those of the control ewes. Two days after this treatment, ovulations occurred in 5 of the treated ewes and in 2 of the control ewes. This induced ovarian activity was not associated with estrous behavior; however, after an adequate subsequent luteal phase all the treated ewes displayed estrus, the resumption of estrus thus being earlier in treated than in control ewes (P < 0.01). In Experiment 3, E 2 supplementation from Day 16 to Day 28 post partum increased the number of LH pulses per 6 hours in suckling ewes (P < 0.05) and induced earlier resumption of estrus in dry ewes but not in suckling ewes (P < 0.01). Luteal function was detected about 5 and 8 days after the insertion of E 2 implants in 4 dry ewes and in 2 suckling ewes, respectively.

Endocrine composition of follicular fluid comparing human chorionic gonadotrophin to a gonadotrophin-releasing hormone agonist for ovulation induction

Concentrations of inhibin, oestradiol and progesterone were determined in pre-ovulatory follicular fluid from 16 women undergoing in-vitro fertilization and embryo transfer treatment. A prospective randomized design was used such that ovulation was induced in eight women with human chorionic gonadotrophin (HCG) (9000 IU), and in eight women with an endogenous surge of luteinizing hormone (LH) and follicle stimulating hormone (FSH) caused by a single injection of gonadotrophin-releasing hormone agonist (GnRHa). Inhibin was measured by an enzyme-linked immunosorbent assay, and oestradiol and progesterone were measured by radio-immunoassay. Concentrations of inhibin and progesterone are significantly higher in follicular fluids collected after ovulation induction with HCG compared with ovulation induction with GnRHa (P < 0.001, P < 0.02, respectively). Concentrations of oestradiol were similar in the two groups. This study shows that the method by which ovulation is triggered significantly affects the micro-environment of the oocyte just prior to ovulation. The results indicate that HCG causes a prolonged luteotrophic effect well before ovulation, compared to an endogenous surge of gonadotrophins caused by GnRHa, and suggest that follicular maturation with an endogenous surge of gonadotrophins may be closer to the natural cycle than those cycles in which HCG is administered for ovulation induction. In addition, this study shows that the concentrations of inhibin and progesterone in follicular fluid may be valuable parameters in assessing the midcycle LH surge requirements for induction of ovulation.

Progesterone ensures full-length luteal phases during the breeding season in ewes

To test the hypothesis that each luteal-phase increase in the serum concentration of progesterone throughout the breeding season prevents a short luteal phase in the next cycle, 22 ewes were treated with an i.v. injection of 10 micrograms gonadotrophin-releasing hormone (GnRH) agonist every 12 h for 33 days beginning on day 12 of a cycle synchronized with prostaglandin F2 alpha. Six days after the last injection of GnRH agonist, ten of the ewes were treated s.c. for 14 days with progesterone-containing silicone elastomer implants to generate luteal-phase serum concentrations. Twenty ewes stopped cycling during GnRH agonist treatment and 16 of these, eight controls and eight treated with progesterone, resumed cycling after the end of treatment. In the control ewes, oestrous cycles began 25.0 +/- 7.5 (S.E.M.) days after the end of GnRH agonist administration, a short luteal phase preceding initiation of cycles in six ewes. In contrast, all eight progesterone-treated ewes resumed cycling synchronously 22.0 +/- 0.2 days after the end of GnRH agonist treatment and all began with full-length luteal phases. These results support the hypothesis that each luteal-phase increment in the serum concentration of progesterone throughout the breeding season prevents a short luteal phase in the next cycle.