Some effects of epidermal growth factor on reproductive function in Merino sheep

Radford, H. M.; Avenell, J. A.; Panaretto, BA

doi:10.1530/jrf.0.0800113

Cited by 14 publications

(10 citation statements)

References 4 publications

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“…The secretion rates of oestradiol-178, progesterone and inhibin were calculated from a knowledge of the plasma concentration, ovarian blood flow and haematocrit (Goding et al 1967). The concentrations of LH (Martensz, Baird, Scaramuzza & Van Look, 1976) and FSH (Radford, Avenell & Panaretto, 1987) were determined in the jugular venous plasma using estab¬ lished radioimmunoassays. Statistical analysis.…”

Section: Methodsmentioning

confidence: 99%

Secretion of Bioactive Inhibin by the Ovary of the Booroola Merino Ewe With or Without a Copy of the Fecundity (F) Gene.

Tsonis

Baird²,

Campbell³

et al. 1988

Journal of Endocrinology

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The secretion rates of bioactive inhibin, oestradiol and progesterone were measured during the mid-luteal phase and at various times during the follicular phase of the cycle by a sensitive bioassay using sheep pituitary cells in culture in 12 Booroola ewes with and without copies of the Fecundity (F) gene in which the left ovary had been auto-transplanted to the neck. Inhibin secretion was high during the luteal phase and fell in the early follicular phase in all genotypes (P less than 0.01). In Booroola ewes with a F/- genotype, inhibin secretion then increased again, towards luteal rates, in the mid and late follicular phases. In Booroola ewes without a copy of the F gene (+/+) inhibin secretion remained low at all three sampling times in the follicular phase. The secretion rate of inhibin at 36 h (P less than 0.1) and 48 h (P less than 0.01) were significantly lower in ewes from the +/+ (no copy of the gene) ewes than in F/- (one copy of the gene) ewes. Oestradiol secretion was low during the luteal phase and increased steadily during the early (24 h) to a plateau in the mid (36 h; P less than 0.01) and late (48 h; P less than 0.05) follicular phase. Progesterone secretion was high during the luteal phase, and decreased to a very low rate by 24 h after prostaglandin (PG) treatment (P less than 0.001) and remained low. At 24 h after PG the concentration of FSH was significantly lower (P less than 0.01) than that during the luteal phase and remained suppressed until the onset of the LH surge.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Methodsmentioning

confidence: 99%

Secretion of Bioactive Inhibin by the Ovary of the Booroola Merino Ewe With or Without a Copy of the Fecundity (F) Gene.

Tsonis

Baird²,

Campbell³

et al. 1988

Journal of Endocrinology

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“…The sensitivity of the assays for LH (Radford et al, 1987a), FSH (Radford et al, 1987b) and progesterone (Avenell el al, 1985) (40) GnRH-immunized ewes treated either soon after birth (prepubertal immunized) or around puberty (peripubertal immunized). The percentage of ewes with measurable antibody titre is given in parantheses.…”

Section: Plasma Concentrations Of Lh and Fsh And Responsiveness Tomentioning

confidence: 99%

Immunization of sheep against GnRH early in life: effects on reproductive function and hormones in ewes

Brown¹,

Mattner²,

Carroll³

et al. 1995

Reproduction

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Groups of Merino ewe lambs were immunized against GnRH either soon after birth (prepubertal) or around puberty (peripubertal) with a prototype commercial preparation and were studied over the following 2 years to determine the long-term effects on reproductive development, function and hormone concentrations. At least 60% of the GnRH-immunized ewes in either treatment group did not experience oestrus and possessed small uteri and small ovaries that lacked follicular development. Growth rates of immunized and control ewes were similar throughout the study. Compared with the increase in plasma LH and FSH concentrations with age in control ewes, the concentrations of these hormones in immunized animals were lower and remained relatively constant from 46 to 90 weeks of age. Plasma FSH concentrations were particularly suppressed in immunized ewes and were significantly (P < 0.05) lower than the control values of 61 and 90 weeks of age. LH release after injection of 1 microgram GnRH at 90 weeks of age was either absent or suppressed in immunized ewes compared with controls. The findings suggest that the lack of GnRH stimulation and consequent deprivation of gonadotrophins, early in the life of ewes, may result in some degree of permanent impairment of hypothalamic and/or pituitary function.

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“…In Exp. 2, EGF was prepared from mouse submaxillary glands by the method of Savage & Cohen (1972) and purified (Radford et al, 1987a). The protein was dissolved in sterile saline (9 g NaCl/1) at appropriate concentrations to obtain a total infused dose over 24 h of 105 pg/kg fleece-free body weight per treated ram.…”

Section: Methodsmentioning

confidence: 99%

“…In ewes, intravenous (i.v.) infusion of mouse EGF (100 µg/kg body weight) reduced LH concen¬ trations by inhibiting the release of LHRH from the hypothalamus (Radford et al, 1987a). It is not known whether treatment of rams with dose rates of mouse EGF required to induce partial or complete break of wool fibres for biological wool harvesting (85-130 µg/kg body weight) produces similar effects on the hypothalamus and gonadotrophin secretion or has any influence on steroido¬ genesis in the testis.…”

Section: Introductionmentioning

confidence: 99%

Effect of mouse epidermal growth factor on plasma concentrations of LH, FSH and testosterone in rams

Brown¹,

Mattner²,

Panaretto³

et al. 1989

Reproduction

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Two experiments were conducted to examine the effects of mouse epidermal growth factor (EGF) on the concentrations of testosterone, LH and FSH in jugular blood plasma and on the pituitary responsiveness to LHRH. In 20 rams treated with subcutaneous doses of EGF at rates of 85, 98 or 113 micrograms/kg fleece-free body weight, mean plasma LH and testosterone concentrations were significantly reduced (P less than 0.05) at 6 h after treatment but not at 24 h. EGF treatment at 130 micrograms/kg fleece-free body weight suppressed the plasma content of these hormones for up to 48 h. Mean plasma FSH concentrations decreased significantly (P less than 0.05) for up to 48 h after EGF treatment, the effect being most pronounced in rams with mean pretreatment FSH values greater than or equal to 0.5 ng/ml. Intravenous injections of 1.0 micrograms LHRH given to each of 5 rams before and at 6 h, 24 h and 72 h after EGF treatment produced LH and testosterone release patterns which paralleled those obtained in 5 control rams similarly treated with LHRH. These results suggest that, in rams, depilatory doses of mouse EGF temporarily impair gonadotrophin and androgen secretion by inhibiting LHRH release from the hypothalamus. Such treatment appears to have no effect on the responsiveness of the pituitary to LHRH.

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Some effects of epidermal growth factor on reproductive function in Merino sheep

Cited by 14 publications

References 4 publications

Secretion of Bioactive Inhibin by the Ovary of the Booroola Merino Ewe With or Without a Copy of the Fecundity (F) Gene.

Secretion of Bioactive Inhibin by the Ovary of the Booroola Merino Ewe With or Without a Copy of the Fecundity (F) Gene.

Immunization of sheep against GnRH early in life: effects on reproductive function and hormones in ewes

Effect of mouse epidermal growth factor on plasma concentrations of LH, FSH and testosterone in rams

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