Radioimmunoassay of a Human Pituitary Prolactin in Plasma

Abstract

A protein fraction with prolactin bioactivities was obtained from the culture medium of human fetal pituitary tissue in long term cultures and termed Pasteels human prolactin (PHP) for convenience. An antiserum was prepared against this human prolactin and used to develop a radioimmunoassay for the material in human plasma. The antigen available (220 µg)was tested against antisera to human growth hormone and to human placental lactogen and in radioimmunoassays for these hormones. The results suggested that the human prolactin fraction contained some immunoreactive human growth hormone (1%). The resulting antibodies in the antihuman prolactin serum could be neutralized by the addition of human growth hormone. The human prolactin also generated antibodies, binding ¹³¹I-labelled human prolactin, which were not neutralized by human growth hormone. This binding was inhibited by plasma from a normal male, 2 normal females and by plasma from a lactating woman after breast feeding. An increase in plasma concentration of the inhibitor, immunologically similar to the human prolactin fraction, was obtained after phenothiazine injection. In the 7 plasma samples tested for human prolactin only 1 contained a detectable concentration of immunoreactive growth hormone. Immunoreactive human placental lactogen (human chorionic somatomammotropin) or any material cross-reacting with anti-HCS serum was undetectable in these plasma samples by a sensitive radioimmunoassay. It is suggested that human plasmas contain detectable amounts of a material immunologically similar to a prolactin fraction isolated from tissue cultures of fetal pituitaries. The fraction and the plasma inhibitor are distinguishable by immunoassay from human growth hormone and from human placental lactogen.

Serum Prolactin Levels during Ovulatory Menstrual Cycle and Menstrual Disorders in Women

“…Radioimmunoassay of human prolactin has been reported by Hwang et al,(1971) : Bryant et al,(1971): L'Hermite et al,(1972 : Jacobs et al,(1972). There have been a few reports of cyclic changes in serum prolactin during menstrual cycles.…”

“…The reason why only human prolactin showed poor development in the research lies in both lack of sensitivity in prolactin bioassay and undevelopment of human prolactin radioimmunoassay. Recently Bryant et al(1971) and Friesen et al(1972) succeeded in human prolactin radioimmunoassay using purified human prolactin and anti human prolactin serum, but these precious antigen and antiserum are not available yet. Quite recently Jacobs et al(1972) devised a new heterologous radioimmunoassay of human prolactin using purified porcine prolactin and anti-ovine prolactin sera.…”

Radioimmunoassay for Human Pituitary Prolactin, Using Antiserum against an Extract of Human Amniotic Fluid

“…The final radioimmunoassay system showed a sensitivity and precision comparable to that of other homologous and heterologous assays for human prolactin [3,4,6,9,14,17]. Addition of hypox plasma was necessary to ensure parallel dose-response curves between dilutions of samples and stand ards.…”

“…H wang et al [12] and F riesen et al [9] described radioimmunoassays which use labelled monkey or human piolactin and antisera against human pituitary prolactin. Homo logous systems, based on material isolated from cultures of human pituitaries, have also been developed [6,19], but these systems do not appear to detect precisely the same material as that measured in other homologous and heterologous assays [11]. Heterologous assays have been described which depend on labelled ovine prolactin and anti-ovine prolactin serum [17], labelled porcine prolactin and anti-ovine prolactin serum [18], and labelled ovine prolactin and anti-human prolactin serum [3,4], A different approach was adopted by J osim ovich et al [14] in using labelled human chorionic somatomammotrophin (HCS) and an antiserum raised against carbamidomethyl-HCS.…”

Prolactin Production by Monkey <i>(Macaca mulatta)</i>Anterior Pituitaries Cultured <i>in vitro</i>

“…Our next step is to obtain purified monkey prolactin and develop a radioimmunoassay. A radioimmunoassay for human prolactin has recently been reported [2,10].…”