F. C. Greenwood

Plasma Prolactin in Goats Measured by Radioimmunoassay: The Effects of Teat Stimulation, Mating Behavior, Stress, Fasting and of Oxytocin, Insulin and Glucose Injections

Results are reported of measuring prolactin in goatplasma by a radioimmunoassay.Changes in concentration in plasma prolactin over time scales from minutes to hours were noted in animals not subject to

Effect of relaxin on prostaglandin E production by human amnion: changes in relation to the onset of labour

Summary. The effect of relaxin on prostaglandin E (PGE) production by human amnion in vitro was investigated. When amniotic discs were incubated in the presence of increasing concentrations of relaxin, two distinct effects were observed. Discs prepared from women delivered by caesarean section before the onset of labour showed a significant decrease in PGE output at relaxin concentrations of 0.5–2 μg/ml; the effect was abolished at higher relaxin concentrations. Discs obtained from women delivered after labour of spontaneous onset responded to the addition of relaxin (4–8 μg/ml) with a significant increase in PGE output, although this increase was only evident in patients in whom labour had started with intact membranes. These results suggest that relaxin, which is present in decidua and chorion laeve at term, may have a paracrine effect on the amnion, inhibiting PGE production during continuing pregnancy but favouring its production during spontaneous labour.

Radioimmunoassay of a Human Pituitary Prolactin in Plasma

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.

Human chorionic gonadotropin β-subunit-like immunoreactive material in the plasma of women wearing an intrauterine progesterone contraceptive system

A systematic study of the presence of human chorionic gonadotropin beta-subunit--like (hCG beta-like) material in the plasma of one woman sampled daily throughout one menstrual cycle and in nine women studied on a selected bleeding schedule has been carried out. Peaks of immunoreactive hCG beta-like activity were found in the follicular and luteal phases of these menstrual cycles which could not be explained by a cross-reaction of luteinizing hormone (LH) in the plasma. The same nine women were studied again 1 month after the insertion of the intrauterine progesterone contraceptive system (IPCS) and again 6 to 8 months later. Although the presence of hCG beta-like immunoactivity correlated with LH values in the cycles studied, there was a significant decrease in its presence 1 month after IPCS use and a highly significant decrease after 6 to 8 months of use.

Relaxin Receptors and a Study of the Physiological Roles of Relaxin

This paper will be divided into two sections, the first dealing with our work on relaxin receptors and the second with the current evidence for relaxin being a physiologically important hormone in the non-pregnant animal.

Ovarian and Decidual Relaxins in Human Pregnancy

The corpus luteum of pregnancy is one source of relaxin in the human (Weiss et al., 1976). Concentrations of relaxin-like immunoactivities in the systemic circulation have been measured by a porcine relaxin RIA (Quagliarello et al., 1979) and more recently by a RIA for synthetic human relaxin (Eddie et al., 1986). The levels of human relaxin in plasma are low in comparison to those in the sow. Peak values attained at between 12–20 weeks are approximately 1 ng/ml, declining thereafter and remaining at between 0.2–0.6 ng/ml for the rest of gestation.

Need for human relaxin.

There are four variations on the porcine relaxin radioimmunoassay which could be used to look at relaxin in human plasma. Each radioimmunoassay has a different degree of heterogeniety with respect to the labelled hormone and to the antiserum, although all are derived from porcine material. The most heterogenous system is that originally used by Bryant in 1972, a labelled hormone selected from NIH-R-P1 relaxin and an antiserum generated to the crude material. A number of other RIAs have been reported (Sherwood et al. 1975; O’Byrne and Steinetz, 1976; Loumaye et al. 1978). A less heterogenous radioimmunoassay is that using pooled relaxins, CM-a’, CM-a, CM-B, from a CMC column used as a label, and an antiserum to the product of an earlier purification step, the G2 area of a Sephadex column (O’Byrne and Steinetz, 1976). This assay is markedly more homogenous with respect to the antigen used for labelling and to that used for immunization. Finally, the most homogenous RIA would be one of these relaxins, CM-a’ and an antiserum to this material (Afele et al. 1979); a system unable to pick up immunoactivity in human plasmas in our hand. In studying these RIAs to look at heterologous relaxins in plasma we have arrived at the following conclusions (Bryant- Greenwood and Greenwood, 1979): the higher the degree of heterogeniety, the more total inhibition can be detected; each RIA looks at a spectrum of plasma immunoactivities related to relaxin but we do not know the structure of the molecules inhibiting in any of the radioimmunoassays; we cannot utilize the physiology of relaxin to support the specificity of heterologous radioimmunoassays.