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ABSTRACT
Human luteal tissue recovered from varying stages of the luteal phase was minced and incubated for 3 h and the effect of human chorionic gonadotrophin (hCG), prolactin and hCG + prolactin on progesterone and oestradiol production measured. While hCG generally enhanced both progesterone and oestradiol synthesis, prolactin alone at either 20 or 200 μg/l had no significant effect on steroidogenesis. When prolactin was added along with hCG in four of six corpora lutea, however, progesterone production significantly increased and in three of six corpora lutea oestradiol production was increased above that induced by hCG alone. It is concluded that prolactin may play some role in the control of steroidogenesis by the human corpus luteum.
J. Endocr. (1984) 103, 107–110
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Serum and plasma from human and domestic animals contain variable amounts of non-specific material(s) which may be mistaken for hormone in assays for human LH and FSH, based upon antisera of high sensitivity and hormonal monospecificity. The non-specific response curves are generally, but not invariably, less steep than those of the hormone standards and endogenous homologous hormones. The levels of non-specific intrusion can be of sufficient magnitude to obscure specific estimations seriously, particularly at low hormone levels, unless the assays are designed to minimize this effect.
The non-specific effects could be minimized (but not abolished) by careful optimization of the assays which involved making the response curve as sensitive as possible and incorporating the serum at a final dilution of 1: 2, since further dilution increased the relative contribution of the non-specific substance(s). The optimized assays require only 48 h of total incubation and show a sevenfold increase in the mean concentration of LH between sera from prepubertal children and adults accompanied by a mean threefold difference in the concentration of FSH.
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ABSTRACT
In order to investigate the development and possible heterogeneity in the luteal population following superovulation, anoestrous ewes were induced to ovulate using progestagen priming followed by injections of pregnant mare serum gonadotrophin (1000 IU) and hCG (1000 IU). Ovaries were recovered from ewes on each of days 2, 4, 6, 8, 10, 12 and 15, and the weight, progesterone content, 125I-labelled hCG binding and progesterone synthesis in vitro of the individual corpora lutea measured. The results obtained showed that plasma progesterone concentrations on the day of slaughter were significantly correlated with time (P<0·05), total weight of luteal tissue (P< 0·001) and number of corpora lutea (P<0·05). The number of corpora lutea recovered per animal ranged from two to 12 and was significantly (P<0·05) correlated with the day after hCG injection until day 10. There was much variation between individual corpora lutea, particularly in terms of weight and progesterone content, although both were significantly (P<0·001) correlated with day of recovery until day 10. 125I-Labelled hCG binding was significantly (P<0·001) correlated with time until day 15. There was a significant (P<0·001) effect of age of the tissue on progesterone production in vitro, with output declining throughout the luteal phase.
These results show that the number of corpora lutea induced by superovulation in anoestrous ewes was very variable, and suggest that ovulation may have continued to occur during the luteal phase. Moreover, there was much variation between individual corpora lutea recovered from the same animal, and thus it should not be assumed that an individual corpus luteum is representative of the entire population.
Journal of Endocrinology (1989) 121, 459–465
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Abstract
The present study was designed to investigate the hormone profiles (oestradiol, LH, FSH, inhibin, progesterone) in high ovulating Meishan sows (MS; n = 9) and in contemporary Large-White hybrid control sows (LW; n = 9) during the follicular phase, the periovulatory period and the early luteal phase. Ovulation rate was higher in MS than LW animals (23·7 and 16·6 respectively; P<0·001) and overall was correlated with the area of the oestradiol peak (P<0·05) and inhibin concentrations (P<0·05). Both the duration of and the area of the oestradiol peak were greater in MS than LW (P<0·01; P<0·02), as were inhibin concentrations both before and after the LH surge (P<0·05). Neither basal nor peak concentrations of LH or FSH differed between the breeds (P>0·05), although FSH concentrations were correlated with the area under the oestradiol peak (P<0·05). Finally, the time-interval from the onset of the LH surge until the rise in plasma progesterone was shorter in MS than LW (54·5 and 74·3 h respectively; P<0·01). In conclusion, these results show for the first time that the higher ovulation rate in MS is associated with enhanced oestradiol and inhibin secretion with no significant difference in LH or FSH concentrations. The more rapid luteinization response to the LH surge by MS in terms of plasma progesterone concentrations may be important in ensuring the high level of embryo survival in this breed.
Journal of Endocrinology (1996) 150, 141–147
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ABSTRACT
The role of FSH in gonadotrophin-releasing hormone (GnRH)-induced follicular development in anoestrous ewes was investigated using injections of bovine follicular fluid (bFF) to reduce plasma FSH levels. Groups of five animals were treated for 12 h with GnRH (250 ng at 2-h intervals) alone, GnRH plus bFF or saline alone, or for 36 h with GnRH alone, GnRH plus bFF or bFF alone. The administration of bFF (1·5 ml s.c. at 8-h intervals) significantly (P<0·05) reduced mean plasma FSH levels, but with the exception of animals treated with bFF alone, had no effect on LH levels. Treatment with bFF alone for 36 h resulted in a significant (P<0·05) increase in LH concentrations. There was considerable variation in the number of follicles ≥2 mm in diameter in the treatment groups. The mean diameter, oestradiol secretion and number of 'oestrogenic' follicles were significantly (P<0·01) reduced in ewes treated with GnRH plus bFF or bFF alone for 36 h compared with those treated with GnRH alone. Testosterone secretion by the follicles was not affected by treatment.
These results confirm previous findings that treatment with bFF decreases circulating FSH levels in anoestrous ewes and, moreover, that concurrent administration of bFF and GnRH inhibits the follicular maturation that is induced by treatment with GnRH alone, suggesting that FSH as well as LH is required for follicular maturation in the ewe.
J. Endocr. (1988) 119, 95–100
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ABSTRACT
Immunization against inhibin consistently results in an increase in ovulation rate in sheep, but the effects that this treatment has on follicle development are unknown. In order to determine the influence of inhibin, parameters of follicle development were assessed in ewes that had been actively immunized against a synthetic peptide homologous to the N-terminal sequence (α1–29, Tyr30) of the a subunit of bovine inhibin, a treatment that neutralizes the biological activity of endogenous inhibin. The final stages of preovulatory follicle development that culminate in ovulation were induced in seasonally anoestrous ewes, and follicles were recovered prior to the predicted time of ovulation. After priming with progestagen, inhibin-immunized and control ewes were treated with gonadotrophin-releasing hormone (GnRH) by continuous infusion (200 ng/h). The ovaries were recovered at slaughter 24 h after the start of GnRH treatment and all follicles ≥ 2·0 mm diameter were dissected out and their capacity to produce oestradiol in vitro was assessed. Further groups of similarly treated animals were blood-sampled daily to determine luteal function following GnRH-induced ovulation. The ovaries were recovered from these ewes at slaughter 10 days after the start of GnRH treatment, the corpora lutea were dissected out and their progesterone content was assessed.
There were more (P < 0·01) follicles of 5–6 mm diameter (3·2 ± 0·45 (s.e.m.) compared with 1·1 ± 0·25 follicles/ewe) and more (P < 0·001) follicles of > 6 mm diameter (2·8 ± 0·56 compared with 0·9 ± 0·17 follicles/ewe) in inhibin-immunized than in control ewes. In addition, the mean number of the antral follicles that were oestrogenic was greater (P < 0·05) in immunized than in control ewes (2·8 ± 0·66 compared with 1·3 ± 0·25 follicles/ewe).
In animals slaughtered 10 days after the start of GnRH treatment, mean ovulation rate was greater (3·17 ± 0·65 and 1·14 ± 0·14, P < 0·01) in inhibin-immunized ewes. Although there was more (P < 0·01) total luteal tissue/ewe in the immunized group, both the mean weight and progesterone content (ng/mg tissue) of individual corpora lutea were similar between treatment groups. Mean plasma progesterone levels increased earlier and reached higher (P < 0·01) mean concentrations in immunized than in control ewes.
These results demonstrate that immunization against inhibin increases the number of preovulatory follicles during the follicular phase, and that steroidogenesis within these follicles and the resultant corpora lutea appears to be normal.
Journal of Endocrinology (1992) 133, 413–419
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ABSTRACT
Analysis of ovine conceptus RNA by slot blotting, Northern analysis and nested polymerase chain reaction failed to detect oxytocin–neurophysin prohormone mRNA. Probes used hybridized with both the 3' end of the prohormone mRNA and the oxytocin-coding sequence. Northern analysis of bovine and porcine conceptus RNA was also negative, and polymerase chain reaction demonstrated oxytocin–neurophysin mRNA in ovine corpus luteum, but not in human corpus luteum or decidua, or in ovine endometrium. Infusion of oxytocin into the uterine lumen in cyclic ewes between days 9 and 19 or 20 after oestrus failed to prolong the luteal phase of the cycle and had no effect on endometrial oxytocin receptor concentrations or uterine prostaglandin F secretion. Oxytocin administered systematically prevented luteolysis and reduced uterine prostaglandin F secretion. Taken together, these data suggest that blastocyst-derived oxytocin is unlikely to contribute to corpus luteum maintenance in early pregnancy. They are inconsistent with a previous report that the ovine blastocyst synthesizes and secretes oxytocin.
Journal of Endocrinology (1991) 130, 443–449
