Exogenous Hormones and Luteal Function in Hysterectomized and Intact Heifers

Brunner, Michael; Donaldson, Lloyd E.; Hansel, William

doi:10.3168/jds.s0022-0302(69)86852-9

Cited by 63 publications

(21 citation statements)

References 11 publications

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“…Oestrogens are thought to act via the uterus since they are not effective in hysterectomized heifers (Brunner et al, 1969). Several studies have shown that oestrogens can modulate uterine PGF-2a production (Caldwell et al, 1972;Barcikowski et al, 1974;Baird, 1978).…”

Section: Introductionmentioning

confidence: 99%

Effects of progesterone and oestradiol-17 on oxytocininduced release of prostaglandin F-2 in heifers

Lafrance

Goff²

1988

Reproduction

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Summary. Seven bilaterally ovariectomized heifers were used in 4 experiments and received: (1) saline injections, as control; (2) one injection of oestradiol (3 mg; i.v.); (3) two i.v. injections of oxytocin (100 i.u.) 6 h apart; or (4) one oestradiol injection 30 min after the first oxytocin injection and a second oxytocin injection 6 h later. All experiments were performed without progesterone and then after 7, 14 and 21 days of progesterone treatment. Frequent blood samples were taken for 1 h before and 7 h after the first injection of oxytocin or oestradiol for the measurement of 13,14-dihydro-15-keto-PGF-2\g=a\ (PGFM) by radioimmunoassay. After 7, 14 and 21 days of progesterone priming, oestradiol caused a significant increase (P < 0\m=.\001) in plasma PGFM after 6 h but not before. After 7, 14 and 21 days of progesterone, there was a significant increase (P < 0\m=.\005) in PGFM after the first oxytocin injection and a similar increase following the second. The oxytocin-induced increase in PGFM after 14 and 21 days of progesterone was significantly higher (P < 0\m=.\001) 6h after oestradiol injection than before the oestradiol injection. There was no significant effect of oestradiol on the response to oxytocin in animals that received no progesterone or in those animals that received progesterone for only 7 days. These results show that, under the influence of progesterone, oestradiol enhances the oxytocin-induced release of PGF-2\g=a\, and suggest a possible synergistic action of these hormones for the induction of luteolysis in heifers.

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Section: Introductionmentioning

confidence: 99%

Effects of progesterone and oestradiol-17 on oxytocininduced release of prostaglandin F-2 in heifers

Lafrance

Goff²

1988

Reproduction

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“…However, involvement of ovarian follicles in control of onset of luteolysis also is likely. Indeed, destruction of large ovarian follicles by X-irradiation (Villa-Godoy et ai, 1985;Fogwell, Cowley, Wortman, Ames & Ireland, 1985) or electrocauterization (Chupín & Saumande, 1981) lengthens the life-span of the CL whereas injections of oestrogens (which originate from large antral follicles) are luteolytic in cattle (Wiltbank, Ingalls & Rowden, 1961;Brunner, Donaldson & Hansel, 1969;Eley, Thatcher & Bazer, 1979;Hixon et ai, 1983). Moreover, inhibition of follicular growth by administration of bovine follicular fluid delays the onset of oestrus (Miller, Critser, Rowe & Ginther, 1979), suggesting that ovarian follicles also are involved in control of onset of oestrus in cattle.…”

Section: Introductionmentioning

confidence: 99%

Ovarian follicular development during early pregnancy in cattle

Guilbault¹,

Dufour²,

Thatcher³

et al. 1986

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Summary. On the day of oestrus (Day 0), 23 cows were assigned randomly to 4 groups in a 2 \ m=x\2 factorial experiment. Main percentage of non-atretic follicles (<4 pycnotic bodies) was lower (P<0\m=.\002) in pregnant than non-pregnant groups in the smallest class of antral follicles (0\ m=. \ 16\ p=n-\ 0\ m=. \ 28mm) but was higher (P<0\m=.\03) in larger classes (0\ m=. \ 68\ p=n-\ 3\ m=. \ 67mm) for pregnant groups. Percentages of atretic follicles were 3\m=.\7and 4\m=.\9(P>0\m=.\1)for follicles of 0\m=.\16\p=n-\0\m=.\67 mm, 91\m=.\1and 78\m=.\9for follicles of 0\m=.\68\p=n-\3\m=.\67mm (P<0\m=.\04) and 5\m=.\1and 16\m=.\1 (P<0\m=.\05) for follicles of 3\m=.\67\p=n-\78\m=.\56mm in pregnant and non-pregnant groups respectively. The percentage of atretic follicles classified as late atretic was higher in pregnant than in non-pregnant groups for follicles of 0\m=.\68\p=n-\1\m=.\57mm (P < 0\m=.\06) and 3\m=.\68\p=n-\8\m=.\56mm (P < 0\m=.\05). The results suggest that, as early as Day 17, the presence of a conceptus favours a more rapid turnover of follicles from class 1 (0\ m=. \ 16\ p=n-\ 0\ m=. \ 28mm) to classes 3 and 4 (0\ m=. \ 68\ p=n-\ 3\ m=. \ 67mm) but limits further growth by increasing atresia.

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“…Conjugated oestrogens are present in the fetal fluids and maternal plasma of the early pregnant cow (Robertson & King, 1975;Eley, Thatcher & Bazer, 1979) and bovine trophoblast is capable of converting androstenedione to free oestrogens in vitro (R. M. Eley, unpublished observation). An experiment was therefore designed to test the possible luteotrophic nature of conjugated oestrone in normally cyclic beef heifers by administration of doses one order of magnitude higher than those reported previously in the literature for free steroids (Wiltbank et al, 1961;Brunner et al, 1969). Maternal peri¬ pheral plasma and fetal fluid ratios of conjugated and free oestrone during pregnancy are similar in magnitude (Eley et al, 1978) and were the basis for the dose used.…”

Section: Introductionmentioning

confidence: 99%

“…Oestradiol is luteolytic in the cow (Brunner, Donaldson & Hansel, 1969;Wiltbank, Ingalls & Rowden, 1961) but luteotrophic in the pig (Gardner, First & Casida, 1963;Frank, Bazer, Thatcher & Wilcox, 1977) when administered during the luteal phase of the cycle. Reports of free oestrogen production by Day-12 pig blastocysts, conjugation of free oestrogens by the pig endometrium and the existence of a sulphatase in the ovary (Perry, Heap, Burton & Gadsby, 1976) implied a luteotrophic nature of the conjugated form.…”

Section: Introductionmentioning

confidence: 99%