Blood plasma concentrations of 13,14-dihydro-15-keto PGF2α (PGFM) were measured in groups of mature non-pregnant and pregnant camels to study PGF2α release patterns around the time of luteolysis and the timing of the signal for pregnancy recognition. Injection of each of four camels with 10 and 50 mg of PGF2α showed clearly that five times the dose of exogenous hormone produced five times the amount of PGFM in peripheral plasma, thereby indicating that, as in other animal species, PGFM is the principal metabolite of PGF2α in the camel. Serial sampling of three non-pregnant camels on each of days 8, 10 and 12, and three pregnant camels on day 10, after ovulation for 8 h showed a significant (P < 0.05) rise in mean plasma PGFM concentrations only on day 10 in the non-pregnant, but not the pregnant, animals. A single intravenous injection of 20, 50 or 100 iu oxytocin given to three groups of three non-pregnant camels on day 10 after ovulation did not increase their basal serum PGFM concentrations. However, daily treatment of six non-pregnant camels between days 6 and 15 (n = 3) or 20 (n = 3) after ovulation with 1–2 g of the prostaglandin synthetase inhibitor, meclofenamic acid, inhibited PGF2α release and thereby resulted in continued progesterone secretion throughout the period of meclofenamic acid administration. These results showed that, as in other large domestic animal species, release of PGF2α from, presumably, the endometrium controls luteolysis in the dromedary camel. Furthermore, reduction in the amount of PGF2α released is associated with luteal maintenance and the embryonic signal for maternal recognition of pregnancy must be transmitted before day 10 after ovulation if luteostasis is to be achieved. However, the results also indicate that, in contrast to ruminants, the release of endometrial PGF2α in the non-pregnant camel may not be controlled by the release of oxytocin.
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