The Effect of Exogenous Progestagen on the Levels of Free Oestrogen in the Ovarian Vein Plasma of the Ewe

Abstract

The levels of free oestrogen (oestrone and oestradiol-17\g=b\) in plasma in the ovarian vein were determined in three groups, each of 27 ewes, at nine intervals at about the time of oestrus. One group had a normal oestrus while the other two had been treated for 16 days with intravaginal sponges containing either 10 or 30 mg of a synthetic progestagen (Cronolone, Searle).In untreated ewes, the mean level (corrected) of oestradiol-17\g=b\ in plasma from the active ovary rose from 25\m=.\3 ng/100 ml at \m=-\48h to a peak of 91\m=.\6 ng/100 ml at 0 h (onset of oestrus) and then fell. There was evidence of biphasic production. The mean level of oestrone was relatively high (13\m=.\0 ng/100 ml) at \m=-\48h; it fell to 2\m=.\0 ng/100 ml between \m=-\36and \m=-\24h and then rose again to 9\m=.\4ng/100 ml at + 12 h. There was no significant change, with time, in the plasma levels of either oestrogen from the non-active ovary. The total amounts of oestradiol-17\g=b\ and of oestrone produced from both ovaries at an oestrous period were estimated to average 9\m=.\7and 2\ m=. \ 4\ g=m\ g.In treated ewes, a similar pattern of production of oestradiol-17\g=b\ was shown by the ewes treated with 30 mg Cronolone. That of ewes treated with 10 mg differed (P < 0\m=.\01). Peak level was reached at an earlier stage, relative to the onset of oestrus, and it declined more rapidly, the total amount of oestrogen produced (oestrone + oestradiol-17\g=b\) was less (10 mg Cronolone, 8\m=.\6 \ g = m\ g ; 30 mg Cronolone, 12\m=.\1 \g=m\g; normal oestrus, 12\m=.\1 \g=m\g), and there was no biphasic production.

The EFFECT OF PROSTAGLANDIN F2α ON PROGESTERONE, OESTRADIOL AND LUTEINIZING HORMONE SECRETION IN SHEEP WITH OVARIAN TRANSPLANTS

“…A biphasic pattern for oestradiol-17/? secretion was reported in normal and progestagen-treated ewes (Smith & Robinson, 1970), and in sheep with utero-ovarian transplants (McCracken et al 1971).…”

Influence of Stage of Cycle, Progestagen Treatment and Dose of Oestrogen on Uterine Motility in the Ewe

“…This was followed by a 10-min period of observation during which the same observer noted the direction in which each uterine contraction was pro¬ pagated. In the entire ewes, the contractions of the uterine horn on the side of the active ovary (Smith & Robinson, 1970) were observed whereas in the ovariectomized ewes, the activity of the right uterine horn was observed. Individual contractions were classified as moving towards the body of the uterus, moving towards the Fallopian tube, stationary, or indefinite.…”

Oestrous Behaviour of the Ewe and the Influence of Treatment With Progestagen

“…It also appears from Table 1 that ramewe response might be significantly altered by progestagen treatment. The in¬ crease in nudging and Flehmen by rams to Treatment ewes accompanied by the increased squatting response of the ewes might be attributed to the abnor¬ mal pattern of production of endogenous oestrogen during and immediately after the terminal stages of progestagen treatment (Smith & Robinson, 1970). If olfactory cues are involved in sexual behaviour in the ram, as seems likely from the results of Lindsay (1965) and Fletcher & Lindsay (1968), it is feasible that target tissues involved in pheromone production may be stimulated by such oestrogen release.…”

“…It has been shown, however, that treatment with progestagen does not result in an identical pattern of production of endogenous oestrogen during and immediately after the terminal stages of treatment. Smith & Robinson (1970) demonstrated that in ewes treated with progestagen there were two 'surges' of oestradiol production which occurred between 48 hr before oestrus and the onset of oestrus. The latter is earlier than that in the normal ewe.…”