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ABSTRACT
Four Romney ewes were actively immunized with a partially purified preparation of inhibin derived from bovine follicular fluid and their ovulation rates in four successive oestrous cycles were compared with those of four ewes receiving adjuvant alone. The ovulation rates of the ewes immunized with the inhibin preparation were significantly higher than those of the control ewes (2·06 ± 0·16 (s.e.m.) vs 1·31±0·06 ovulations/ewe, n= 4). Plasma concentrations of FSH and LH, measured in blood samples taken three times a week for 11 weeks, during which time each ewe was immunized three times, were not significantly different between the two treatment groups. These results suggest that active immunization with inhibinenriched follicular fluid may be a potential means of increasing fecundity in sheep.
J. Endocr. (1984) 102, 305–309
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Laboratory of Veterinary Physiology, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183, Japan
(Received 2 May 1977)
When an amount of human chorionic gonadotrophin (HCG) sufficient to cause ovulation is given to 4-day cyclic rats on the day of dioestrus, premature ovulation is induced the next morning (Eto & Imamichi, 1955). The pattern of release of follicle-stimulating hormone (FSH) responsible for the initiation of follicular maturation of the next set of follicles (Schwartz, 1969; Welschen & Dullaart, 1976) after HCG-induced ovulation has not been previously evaluated. The present communication is concerned with this problem and indicates that a large amount of FSH is released within 12 h of administration of HCG, with only a small concomitant rise in the concentration of luteinizing hormone (LH).
Adult female Wistar rats were maintained under a 14 h light : 10 h darkness schedule (lights on 05.00 h), and those showing three or
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I.N.R.A., Station de Physiologie de la Reproduction, 37380 Nouzilly, France
(Received 5 July 1974)
Plasma levels of oestradiol-17β (OE) and progesterone are correlated with the ovulation rate of pregnant mare serum gonadotrophin (PMSG)-treated cattle (Henricks & Lamond, 1972; Lemon & Saumande, 1972). No correlation was found however between the size of the preovulatory discharge of luteinizing hormone (LH) and OE secretion or the ovulation rate (Henricks, Hill, Dickey & Lamond, 1973).
To study the relationship between plasma OE and LH concentrations and the ovulation rate of cattle, seven cows and six heifers were treated to produce superovulation by giving 1600 i.u. PMSG on day 16 of the cycle (day 0 = day of oestrus) and 1500 i.u. human chorionic gonadotrophin (HCG) at the onset of the next oestrus [used to induce multiple pregnancies in our laboratory (Mauleon, Mariana, Benoit, Solari & Chupin, 1970)]. Blood was collected by acute puncture of
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SUMMARY
The effect of treatment with prostaglandin F2α (PGF2α on luteal function was examined in hysterectomized guinea-pigs. Regression of corpora lutea was found to occur when 0·25 mg (or more) was injected daily for 3 days and ovulation usually ensued within 5 days after treatment. The administration of 1 mg PGF2α daily for 7 days caused marked luteolysis but ovulation did not occur. Ovulation was blocked in three of four intact female guinea-pigs given 1 mg PGF2α/day for 7 days from day 15, but took place normally in five females injected with 0·25 mg/day. Treatment of hysterectomized guinea-pigs with 0·62 mg adrenaline hydrochloride/day, 1·97 mg atropine sulphate/day or 0·52 mg histamine dihydrochloride/day did not cause luteal regression, while the injection of 0·25 mg or 1 mg prostaglandin E2 daily for 3 days was likewise ineffective.
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ABSTRACT
The effects were analysed of a unilateral lesion in the anterior or medial hypothalamus made on the day of oestrus on right or left hemicastrated rats. On the day of oestrus after two consecutive oestrous cycles of the same length, the ovulation rate in rats with lesions in the anterior left hypothalamus was lower than in control hemicastrated animals (5/16 vs 18/20; P<0·01), and normal in those rats with lesions in the right side (14/18). None of the animals with lesions in the left side of the anterior hypothalamus and with the left ovary in situ ovulated (0/7), but 5/9 with the right ovary in situ did ovulate (P<0·05). Lesions on either side of the medial hypothalamus did not modify ovulation rate. Compensatory ovulation was reduced in those animals with lesions in the right anterior hypothalamus and with the right ovary in situ. Lesions in either side of the medial hypothalamus reduced compensatory ovulation. Lesions in the right side of the anterior and medial hypothalamus increased compensatory ovarian hypertrophy in the left ovary and decreased it in the right ovary. Lesions in the left side of the anterior hypothalamus increased compensatory ovarian hypertrophy in the left ovary only, whereas lesions in the left side of the medial hypothalamus reduced compensatory ovarian hypertrophy in the right ovary. The results suggest that the information arising in each side of the anterior and medial hypothalamus plays different roles in the ipsi-and contralateral ovary, when either the left or the right ovary is absent.
Journal of Endocrinology (1990) 124, 37–41
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In rats with 4- or 5-day reproductive cycles various responses to the blockade of ovulation with sodium pentobarbitone at pro-oestrus (or at pro-oestrus and on the next day) were compared. The blood concentrations of oestradiol decreased rapidly during the 24 h period after injection of sodium pentobarbitone at pro-oestrus in rats with 5-day cycles. In those with 4-day cycles this response took almost a day to develop. Injection of sodium pentobarbitone at pro-oestrus and on the next day interfered with ovulation of the present crop of large follicles in rats with 5-day cycles. In 4-day cyclic rats this procedure delayed ovulation of these follicles by 48 h. Receptive behaviour was absent on the day after the second injection of sodium pentobarbitone in rats with 5-day cycles; some receptivity was, however, induced by the injection of gonadotrophin. The latter injection resulted in the release of a low number of eggs; fertilization of these eggs, however, did not occur. In 4-day cyclic rats receptive behaviour was recorded on the day after the second injection of sodium pentobarbitone: fertilization of delayed ovulated eggs took place normally but pregnancy was seen only rarely.
The results indicated clear differences in responses to blockade of ovulation with sodium pentobarbitone between rats with 4- or 5-day cycles. The differences most probably result from a more advanced 'age' of preovulatory follicles at pro-oestrus of 5-day cycles compared with those of 4-day cycles. Experimental delay of ovulation reveals ageing changes and the probable onset of atresia at an earlier time after blockade in 5-day cyclic than in 4-day cyclic rats.
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In immature rats primed with pregnant mare serum gonadotrophin, antiserum to progesterone could prevent or reduce ovulation in response to injected human chorionic gonadotrophin (HCG). To be effective, antiserum treatment had to be within 6 h of gonadotrophin treatment; antiserum given 9 h after HCG was ineffective. Progesterone restored the antiserum blocked ovulation completely or incompletely when administered intravenously within 6 h of treatment with HCG. The first 6 h was shown to be a progesterone-dependent step in the ovulatory process in this experimental system.
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ABSTRACT
In late-prepubertal female rats passive immunoneutralization of endogenous inhibin was achieved by injection of inhibin antiserum. Effects on follicle population, timing of sexual maturation, ovulation rate at first and second oestrus and serum FSH levels were studied.
Rats were injected with antiserum, (non-immune) control serum from castrated sheep (castrated serum) or their IgG fractions, or with saline on day 33 or 3 or 2 days (days −3/−2) before the expected day of first ovulation, day 38·5±0·2 (n = 70). Blood was collected from different subgroups at 8, 24 and 48 h, and at first and second oestrus after injection. At necropsy, ovaries were histologically prepared for differential counting of follicles (48 h and first oestrus) and counting of corpora lutea (CL; first and second oestrus) as an index of ovulation rate.
Results from rats injected with either serum or its IgG fraction were not different, as was the case when rats were injected with either castrated serum or saline. Thus, results from groups treated with antiserum and antiserum IgG were combined and labelled 'antiserum', and the castrated serum, castrated serum IgG and saline-treated groups were combined and labelled 'control'. The activity of inhibin-neutralizing antibodies in the circulation of antiserum-treated rats was reduced by 43% between 8 h and second oestrus after injection, as determined by the binding of purified bioactive radioiodinated 31 kDa bovine inhibin.
After antiserum injection on day 33, more healthy antral follicles (vol. > 100 × 105 μm3, diameter > 260 μm) were present in the ovaries at 48 h (70·6 vs 54·4; P < 0·05) and at first oestrus (73·1 vs 50·8; P < 0·05) if first oestrus was reached within 5 days, but numbers were not different if first oestrus was more than 5 days after injection (52·6 vs 50·8). The number of CL after injection of antiserum on day 33 was increased at first oestrus compared with control (13·4±0·5, n = 30, vs 10·0±0·2, n = 40; P<0·001), an effect that was even more clearly present in antiserum-injected rats ovulating within 5 days (14·4±0·7, n = 20; P < 0·001).
Rats injected with antiserum at days −3/−2 showed a doubling of ovulation rate at first oestrus when compared with control animals (21·5±0·8, n = 12, vs 10·5±0·2, n = 15; P < 0·001). No differences in the number of CL was seen at second oestrus. Age and body weight on the day of first ovulation were not influenced by antiserum treatment.
Serum FSH was significantly (P < 0·01) increased at 8 h after antiserum injection on either day 33 or on days −3/−2 to a level of 250 and 800% of control levels respectively.
Thus, injection with inhibin–neutralizing antiserum into prepubertal female rats resulted, through an increase in serum FSH concentration 8 h after injection, in the growth of additional numbers of healthy antral follicles. Supranormal ovulation rate occurred if antiserum injections were given within the last 5 days before first ovulation, with a maximal ovulation rate after injection on days −3/−2. The data support the view that, in the immature female rat during the last 5 days before the day of first ovulation, inhibin is (through its regulation of serum FSH levels) progressively involved in the control of follicle growth and ovulation rate.
Journal of Endocrinology (1991) 130, 289–296
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SUMMARY
1. Sixty crossbred maiden ewes, twelve of which were hysterectomized, and eighteen mature ewes were used during the non-breeding season in two experiments involving injection with 75 mg of progesterone intramuscularly and 1000 i.u. of pregnant mare serum (PMS) subcutaneously, either alone or in combination.
2. Progesterone given as two daily injections of 12·5 mg each for 3 days, followed 2 days later by 1000 i.u. of PMS resulted in oestrus with ovulation in sixteen out of eighteen ewes treated. The two remaining ewes failed to ovulate owing to the presence of active corpora lutea.
3. Three injections of 25 mg progesterone/day, or a single injection of 75 mg progesterone followed by PMS, were decreasingly less effective in inducing oestrus.
4. Progesterone alone in the form of two daily injections of 12·5 mg for 3 days without subsequent PMS, was followed by ovulation in five out of six mature ewes, three of them exhibiting oestrus and producing lambs subsequently.
5. Time relationships were physiologically normal, oestrus commencing 24 to 36 hr after PMS and preceding ovulation by 10–20 hr. The ovaries showed no histological abnormalities.
6. Hysterectomized and intact ewes responded alike, suggesting that the conditioning effect of progesterone is a central phenomenon.
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SUMMARY
A possible involvement of oestrogens in regulating the ovulatory release of luteinizing hormone (LH) has been explored by using an oestrogenantagonist, clomiphene. When given orally in the afternoon on the day before pro-oestrus to rats with a 4-day cycle, the compound prevented ovulation on the morning of oestrus. This was not associated with interference with vaginal cornification, uterine ballooning or mating. Similarly, clomiphene prevented ovulation in hamsters when given at a corresponding stage of the cycle. In adult rats ovulation could be fully restored by the intravenous administration of LH or LH releasing factor at 14.00 hr. on the day of pro-oestrus. Oestradiol benzoate given simultaneously with clomiphene on the day before pro-oestrus or the stimulus provided by mating on the night of pro-oestrus were also effective in this respect. It is implicit in these findings that clomiphene interferes with ovulation by virtue of its anti-oestrogenicity. This indicates that a positive feedback of oestrogen is an integral part of the chain of events culminating in the ovulatory release of LH in the reproductive cycle.
