Factors Affecting the Plasma Prolactin Level in the Cow and the Goat as Determined by Radioimmunoassay

Abstract

SynopsisPlasma prolactin concentration of serial blood samples taken from cows and

Prolactin Release in the Sheep

“…Saji (1967) who used the haemagglutination-inhibition assay for measuring prolactin. These results differ substantially from those reported by Arai & Lee (1967) (Johke, 1970) and hand milking in the goat (Hart, 1972) (Bryant & Greenwood, 1968;Davis et al, 1971;Cumming, Brown, Goding, Bryant & Greenwood, 1972) Prolactin levels are expressed in ng/ml plasma. 1965; Bryant, Linzell & Greenwood, 1970;Johke, 1970;Neill, 1970;Butler, 1971;Raud, Kiddy & Odell, 1971;Cumming et al, 1972;Frantz, Kleinberg & Noel, 1972;Fell, Findlay, Cumming & Goding, 1973 (1971) and Fell et al (1972).…”

“…These results differ substantially from those reported by Arai & Lee (1967) (Johke, 1970) and hand milking in the goat (Hart, 1972) (Bryant & Greenwood, 1968;Davis et al, 1971;Cumming, Brown, Goding, Bryant & Greenwood, 1972) Prolactin levels are expressed in ng/ml plasma. 1965; Bryant, Linzell & Greenwood, 1970;Johke, 1970;Neill, 1970;Butler, 1971;Raud, Kiddy & Odell, 1971;Cumming et al, 1972;Frantz, Kleinberg & Noel, 1972;Fell, Findlay, Cumming & Goding, 1973 (1971) and Fell et al (1972). It is tempting to associate this with the rapid rise in free circulating oestrogens and the decrease in progesterone that takes place at this time (Challis, 1971;Obst & Seamark, 1972;Chamley & co-authors, 1973;Robertson & Smeaton, 1973), but a careful study of the time sequence of these events is necessary before any more definite conclusions can be drawn.…”

Prolactin Release in Cattle

“…Independent of the extreme extent of the prolactin inhibition there were distinct differences concerning the influence of the drug on lactation, whether the inhibitor was applied before or during the onset of lactation (lactogenesis) or later during already established lactation (galactopoiesis) Text- fig. 1 (Johke, 1970;Tucker, 1971;Raud, Kiddy & Odell, 1971 ;Schams, 1973) (Johke, 1969(Johke, , 1970Fell, Beck, Blockey, Brown, Catt, Cumming & Goding, 1971;Tucker, 1971;Koprowski, Convey & Tucker, 1971;Schams & Böhm, 1972;Schams, 1972a;Reinhardt 8c fig. 3).…”

“…may be within the complex. We do not interpret this peak as being functional or essential either for the onset of lactation or for parturition (Johke, 1970;Fell et al, 1971), but no seasonal influences were taken into account. Our earlier observation Karg 8c Schams, 1970), that the 'pacemakers' for the basic level of prolactin are primarily the seasonal rhythms, is being confirmed.…”

The Relationship Between Lactation and the Release of Prolactin and Growth Hormone in the Goat

“…the onset of mild . Oxytocin (o) (Johke, 1970;Bryant, Linzell & Greenwood, 1970;Hart, 1973b); it seems likely, therefore, that the increases in plasma prolactin concentration during parturi¬ tion were due to stress, possibly associated with the distension of the cervix and vagina during delivery.…”