PLASMA PROLACTIN, GROWTH-HORMONE AND PROGESTERONE CONCENTRATIONS IN PSEUDOPREGNANT, HYSTERECTOMIZED AND PREGNANT GOATS

Jugular plasma prolactin (PRL), growth hormone (GH) and progesterone ( P4) levels were estimated in goats under three different conditions wi th prolonged luteal function (P4 greater than or equal to 1 ng/ml): ps eudopregnant animals (n = 4), goats hysterectomized during early pregn ancy (n = 4) and does with normal pregnancy (n = 4). Mean duration (+/ -S.E.M.) of luteal phases were 189 +/- 20, 171 +/- 10, and 147 +/- 2 d ays in the three groups, respectively. Until day 120, mean PRL levels were below 150 ng/ml in each group. After day 120 of the luteal phase, PRL concentrations were significantly higher than before, but continu ed to increase up to 800 ng/ml only in pregnant animals around parturi tion. Mean GH levels varied between 2 and 3 ng/ml in animals of each g roup during the luteal phase. Only after parturition, a significant el evation occurred. P4 levels in pseudopregnant animals were significant ly lower than in the other two groups between days 10 and 55, and show ed a gradual but continuous decline towards the end of the luteal phas e. After hysterectomy of early pregnant animals, P4 concentrations dec reased to levels measured in pseudopregnant animals but were significa ntly higher again as compared to pseudopregnant animals between days 1 21 and 150. It is concluded that a pseudopregnant condition, character ized by intrauterine fluid accumulation, is not related to increased p lasma PRL and GH concentrations. The low and gradually decreasing plas ma progesterone levels in the pseudopregnant animals probably reflect the absence of a luteotrophic stimulus by the conceptus. The progester one profile in the animals that were hysterectomized during early preg nancy suggests that the corpora lutea of these does have been permanen tly changed by the presence of the conceptus during the first weeks of the luteal phase. (C) 1997 Elsevier Science B.V.