Levels of progesterone and changes in prostaglandin F-2 alpha 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 mater nal recognition of pregnancy were determined in the blood of Ilamas mated e ither with an intact or a vasectomized male. The ability of flunixin meglum ine (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 p attern of prostaglandin release was recorded during luteolysis in non-pregn ant Ilamas, giving further support to the hypothesis that PGF(2 alpha) is t he luteolytic agent in Ilamas. The mean number of peaks per animal rose fro m 0.3 on day 7 to 3.8 on day 10 and then declined to 1.1 on day 12 with cor responding mean peak amplitude changing from 465 to 1734 and 566 pmol l(-1) , respectively. In pregnant Ilamas, prostaglandin pulsatile release also oc curred. The mean number of peaks per animal rose from 0.4 on day 7 to 0.8 o n day 10 and then declined to 0.2 on day 11 and 0.6 on day 12, with corresp onding mean peak amplitude changing from 491 to 676, 388 and 547 pmol l(-1) , respectively. The transient decrease and subsequent recovery in progester one concentrations was observed to occur in connection with prostaglandin r elease 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)). Concentra tions of PGFM decreased rapidly after the first administration of FM and re mained 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 sug gested that a higher dose and/or a more intensive injection schedule is req uired in Ilamas than in other ruminants to prevent luteolysis. (C) 2000 Els evier Science B.V. All rights reserved.