Progesterone Concentrations In Samples Research Articles

Role of LH in luteolysis and growth of the ovulatory follicle and estradiol regulation of LH secretion in heifers

The role of LH in luteolysis and development of the ovulatory follicle and the involvement of GnRH receptors in estradiol (E2) stimulation of LH secretion were studied in heifers. A pulse of PGF2α, as indicated by a metabolite, was induced by E2 treatment on Day 15 (Day 0 = ovulation) and LH concentration was reduced with a GnRH-receptor antagonist (acyline) on Days 15, 16, and 17. Blood samples were collected every 6 h on Days 14–17 and hourly for 10 h beginning at the Day-15 treatments. Four groups were used (n = 6): control, acyline, E2, and E2/acyline. The number of LH pulses/heifer during the 10 h posttreatment was greater (P < 0.0002) in the E2 group (2.3 ± 0.4, mean ± SEM) than in the acyline group (0.2 ± 0.2) and was intermediate in the E2/acyline group (1.4 ± 0.2). Concentrations of progesterone in samples collected every 6 h on Day 15 showed a group-by-hour interaction (P < 0.02); concentrations decreased in the acyline group but not in the control group. The 12 heifers in the combined acyline and E2/acyline groups had three follicular waves compared to two waves in 10 of 12 heifers in the combined control and E2 groups. Results (1) supported the hypothesis that LH delays the progesterone decrease associated with luteolysis, (2) supported the hypothesis that LH has a positive effect on the continued development and growth of the selected ovulatory follicle, and (3) indicated that E2 stimulates LH production through an intracellular pathway that involves GnRH receptors on the gonadotropes and a pathway that does not involve the receptors.

Timed Artificial Insemination with Estradiol Cypionate or Insemination at Estrus in High-Producing Dairy Cows

A total of 799 Holstein cows from 3 herds were randomly assigned at 37±3 d in milk (DIM) to timed artificial insemination (AI) or insemination at detected estrus. Cows were presynchronized with injections of PGF2α at 37 and 51 DIM. At 65 DIM, cows received an injection of GnRH, followed 7 d later by PGF2α. Cows in the estrus-detected group were inseminated after being observed in estrus during the 7 d after the last PGF2α. Cows in the timed AI group received an injection of 1mg of estradiol cypionate (ECP) 24h after the last PGF2α. If detected in estrus≤24h after ECP, cows were inseminated then or at a fixed time 48h after ECP. Pregnancy was diagnosed by ultrasonography at 30 d and by palpation at 44 and 58 d after AI. Plasma progesterone was measured in 4 samples per cow collected on days of 1) second PGF2α, 2) GnRH, 3) third PGF2α, and 4) 48h after third PGF2α. Cows were classified as cyclic or anovulatory based on progesterone concentrations in samples 1 and 2. Similarly, cows were classified according to progesterone concentrations in samples 2, 3, and 4 (H = ≥1 ng/mL; L = <1 ng/mL), resulting in 8 combinations (LLL, LHL, LLH, LHH, HHH, HHL, HLH, and HLL). Conception rates and pregnancy rates were higher for cows in the timed AI group than in the estrus-detected group at 30, 44, and 58 d (e.g., at 58 d, pregnancy rates were 42.2% for multiparous cows or 34.4% for primiparous cows in the group receiving ECP and timed AI compared with only 20.8 or 18.8% for respective parity subgroups for the treatment group inseminated only at detected estrus). Pregnancy losses were 11.5% from 30 to 58 d and did not differ between treatments. Cyclic cows within both treatments had higher estrous responses, conception rates, and pregnancy rates. Cows that responded to presynchronization and to luteolysis (HHL) had the highest conception and pregnancy rates, followed by cows classified as LHL. Use of 1mg of ECP to induce ovulation as part of a synchrony regimen improved reproduction at first postpartum insemination in dairy cows.

Social dominance of female goats affects their response to the male effect

The aim of this study was to assess the influence of social rank of anestrous goats on their interval to ovulation after exposure to males. Forty-five adult females were observed before and after the introduction of males to their pen. Behavioural sampling was used in both periods to record agonistic interactions. An index of success (IS) for each goat, based on its ability to displace other individuals was then calculated and three ranking categories were designated, low, medium, and high-ranking goats. When the goats were exposed to the male, scan sampling every 5 min was used to record the position of each goat with respect to the male. An index of association (IA) with the male was then calculated for each goat. The time of ovulation was determined through progesterone concentrations in samples taken daily for 30 days after the introduction of the males. The time of conception was retrospectively calculated after kidding. Analysis of variance and Mann–Whitney tests were used to compare the intervals from the introduction of the males to ovulation and to conception between categories. Spearman correlations were used to relate the time of ovulation with the indices of success and association, as well as within each index. High and medium ranking goats ovulated before low-ranking individuals ( P<0.05). A total of 32 goats (76%) ovulated after the introduction of the males to the pen. The percentages of females ovulating in the high, medium, and low-ranking groups were 81.8% (9/11), 75% (12/16) and 73% (11/15), respectively ( P>0.05). High-ranking females conceived earlier than the other two categories ( P<0.05). The time from exposure to the male to ovulation was negatively correlated with the index of success (Rs=−0.49, P<0.05) and with the index of association of the female with the male (Rs=−0.58, P<0.05). A positive correlation was found between a doe’s index of success and her index of association with the male (Rs=0.64, P<0.01). It is concluded that after the introduction of males, the high-ranking goats are the first individuals to ovulate and to conceive, probably due to the more intense stimulation that results from their closer association to the males.

Effect of gonadotrophin-releasing hormone agonist-induced suppression of LH and FSH on follicle growth and corpus luteum function in the ewe.

Continuous infusion of a gonadotrophin-releasing hormone (GnRH) agonist (buserelin) by osmotic minipump from day 1 of the luteal phase in five Welsh ewes resulted in a sustained suppression of plasma concentrations of FSH which increased three- to eightfold within 2 days after the end of infusion 29 days later. Plasma concentrations of LH increased three- to eightfold over the first 5 days of infusion and then became basal and non-pulsatile until 1 day after the end of infusion. Duration of the luteal phase and plasma concentrations of progesterone were not significantly different in control and treated ewes. Pulses of LH in control ewes were followed by increases in concentrations of progesterone in samples collected at 10-min intervals for 7 h on days 10 and 14 of the luteal phase. However, progesterone was also released in a pulsatile manner in the absence of LH pulses in both control and GnRH agonist-treated ewes. After natural luteolysis, no ovulation or corpus luteum function occurred in treated ewes up to 15 days after the end of treatment on day 29, even though oestrus, indicating follicular development and oestrogen secretion, had occurred 8-11 days after treatment ended. After 30 days of infusion the ovaries of GnRH agonist-treated ewes contained no follicles greater than 2.5 mm in diameter. In follicles of 1-2 mm in diameter the basal and LH-stimulated production of oestradiol and testosterone in vitro were similar in both control and GnRH agonist-treated ewes, and a similar proportion of these follicles was oestrogenic (greater than 370 mol oestradiol per follicle) in GnRH agonist-treated and control ewes. These results show (1) that progesterone secretion by the corpus luteum of the ewe can be sustained in the presence of basal concentrations but absence of pulsatile secretion of LH, and progesterone is released in a pulsatile manner whether or not LH pulses are present, (2) that follicular development beyond 2.5 mm in diameter in the ewe is dependent upon adequate stimulation by both LH and FSH and (3) that the continuous infusion of GnRH agonist is a simple method for providing reproducible suppression of LH and FSH and follicular development in the ewe to allow the study of gonadotrophin action on the ovary in vivo.

In vitro metabolism of ovarian steroids by bovine whole blood and plasma

Experiments were conducted to evaluate the effects of time and temperature on the potential of bovine whole blood (WB) or plasma (PL) to metabolize the ovarian steroids progesterone, estradiol-17β and testosterone. During a radioimmunoassay study (Experiment 1), we observed a temperature and time-dependent reduction (P<0.001) of plasma progesterone concentrations in samples incubated as WB at 5, 15, 25, or 35C for up to 48 hr. Most notable was the observation that 27% of progesterone present in controls was lost when WB was incubated at 5C for 48 hr and a 17% reduction was observed when PL samples were incubated at 35C for 48 hr. Immunoreactive estradiol-17β concentrations (Experiment 2) in PL and WB incubates were not affected by time or temperature. However, immunoreactive testosterone concentrations increased more than 3-fold by 48 hr in WB incubates held at 35C. To examine the latter observation further, 3H-progesteone was incubated with WB at 35C, followed by extraction and thin-layer chromatography (Experiment 3). Results generally supported RIA findings and revealed the presence of significant 17α-hydroxylase, 17–20 lyase and aromatase activity. Heretofore this has not been considered to occur outside major steroid metabolizing organs.

Salivary steroid assays for assessing variation in endocrine activity

Salivary sampling regimens are non-invasive, and therefore facilitate dynamic tests of hormone function and assessment of biological rhythms. Concentrations of neutral steroids in saliva are independent of flow rate and appear to reflect the non-protein-bound, 'free' fraction. Comparison of replicate determinations of quality control pools with determinations of samples collected at 2 min intervals allows the significance of short-term fluctuations in cortisol and testosterone secretory activity to be estimated. Samples collected at 15 min intervals provide a convenient way to estimate circadian rhythms, particularly in young children. Determination of salivary progesterone concentrations in samples collected by women daily, over extended periods of time, provides a valuable means of assessing ovarian function. Such assays may be used to monitor ovulation-induction therapy.