Radioimmunoassay for ovine prolactin. The secretion of prolactin as affected by milking, oestradiol administration and onset of parturition

Secretion of Prolactin and Luteinizing Hormone at Oestrus in the Ewe

“…This raised the possibility that there could be a common mechanism causing the release of these hormones. This was con¬ firmed by the finding of Fell, Beck, Brown, Cumming & Goding (1972) that oestradiol administered to anoestrous ewes caused, after a 5-10 h interval, the release of prolactin as well as LH. However, this is probably not the sole mechanism responsible for prolactin release.…”

Prolactin and the control of gonadotrophin secretion in the female

“…1). Since administration of oestradiol will result in an increase in circulating levels of prolactin (Fell, Beck, Brown, Cumming & Goding, 1972), it has been suggested that the pro-oestrous rise in prolactin in the sheep, as in the rat, is related to the increasing levels of oestradiol during the periovulatory period. However, a closer examination of the time course of release of prolactin in relation to the secretion of oestradiol suggests that the increase in prolactin occurs before any dramatic change in circulating levels of oestradiol (A. S. McNeilly & D. T. Baird, unpublished observations; Text- fig.…”

An Analysis of Specific Stimuli Causing the Release of Prolactin and Growth Hormone at Milking in the Goat

“…Radioimmunoassay techniques have established beyond reasonable doubt that suckling and milking are potent stimuli for the release of prolactin from the anterior pituitary of the rat (Kwa & Verhofstad, 1968), goat (Bryant, Greenwood & Linzell, 1968), cow (Johke, 1969), sheep (Fell, Beck, Brown, Cumming & Goding, 1972) and woman (Hwang, Guyda & Friesen, 1971); although in the case of ruminants the efficacy of the stimulus may be modified by the effect of season (Hart, 1975a, b). The effects on growth hormone (GH) secretion have been less consistent.…”