Levels of progesterone and changes in prostaglandin F2α release during luteolysis and early pregnancy in llamas and the effect of treatment with flunixin meglumine

The secretory patterns of progesterone in relation to concentrations of 15-ketodihydro-PGF(2 alpha) (PGFM) during the period of luteolysis or of maternal recognition of pregnancy were determined in the blood of Ilamas mated either with an intact or a vasectomized male. The ability of flunixin meglumine (FM) to postpone luteolysis in non-pregnant Ilamas was investigated by injecting the drug intravenously every 6 h at a dose of 2.2 mg/kg from days 6 to 12 post-copulation into a group of non-pregnant Ilamas. A pulsatile pattern of prostaglandin release was recorded during luteolysis in non-pregnant Ilamas, giving further support to the hypothesis that PGF(2 alpha) is the luteolytic agent in Ilamas. The mean number of peaks per animal rose from 0.3 on day 7 to 3.8 on day 10 and then declined to 1.1 on day 12 with corresponding mean peak amplitude changing from 465 to 1734 and 566 pmol l(-1), respectively. In pregnant Ilamas, prostaglandin pulsatile release also occurred. The mean number of peaks per animal rose from 0.4 on day 7 to 0.8 on day 10 and then declined to 0.2 on day 11 and 0.6 on day 12, with corresponding mean peak amplitude changing from 491 to 676, 388 and 547 pmol l(-1), respectively. The transient decrease and subsequent recovery in progesterone concentrations was observed to occur in connection with prostaglandin release during early pregnancy. Oestmdiol-17 beta plasma peak concentrations attained after luteolysis were significantly higher than those recorded in early pregnant animals (around 30 pmol l(-1) and II pmol l(-1)). Concentrations of PGFM decreased rapidly after the first administration of FM and remained low throughout the first 2 days of treatment. Thereafter, pulsatile release of prostaglandins started, and luteolysis proceeded; but a delay of 1-1.5 days in the progesterone decline was observed. Thus, it might be suggested that a higher dose and/or a more intensive injection schedule is required in Ilamas than in other ruminants to prevent luteolysis. (C) 2000 Elsevier Science B.V. All rights reserved.