Summary. Baboon CG from the urine and placenta (Days 33–45 of gestation) was purified by ammonium acetate/alcohol extraction followed by ionic exchange, gel filtration and affinity chromatography. The CG activity was monitored using a double-antibody radioimmunoassay utilizing anti-baboon CG and hCG both as the labelled ligand and standard. Biological activity was measured by the rat luteal cell radio-receptor assay. The purified preparation exhibited heterogeneity in terms of its behaviour during ionic exchange chromatography and isoelectric focussing. Like hCG, baboon CG was made up of two non-covalently linked subunits: the Stokes' radii were 36·5, 29·0 and 22·0 × 10−10 m for native CG, the beta subunit and the alpha subunit. The material focussed between pH 4·2 and 5·5. Relative to the second international hCG standard the biological potency of the purified urinary baboon CG was 4058 i.u. whilst the immunological activity was 4364 i.u. It is concluded that baboon and human CG are very similar with respect to their physicochemical properties and that baboon CG can be purified by the methods that have been developed for hCG.
C. S. Bambra and S. Gombe
Summary. Treatment of rats with anti-PMSG and anti-hCG for 5 days from Days 6,11 or 16 of pregnancy caused variable necrosis of fetal tissue, the extent of which increased from the chorionic cells to the inner trophoblastic layers with the increase in dose from 4 to 10 mg anti-PMSG. At 10 mg/day, fetal death and resorption were invariable in early to mid-pregnancy, whilst in late pregnancy some litters were carried to term. The main histological change in the corpora lutea was hyperaemia in the anti-PMSG-treated rats. Immunofluorescence studies with conjugates of anti-hCG and anti-PMSG showed sharp localization in the giant and chorionic cell layer at the feto-maternal junction.
We conclude that an hCG/PMSG-like substance is produced by rat chorionic cells and that it plays an immunosuppressive role during pregnancy.
C. S. Bambra and R. Tarara
Summary. An immunohistochemical technique using a high specificity antiserum against baboon CG was used to demonstrate the presence of a CG-like material on: (1) fixed baboon placental sections collected between 31 and 39 days of gestation, (2) trophoblast monolayers derived from hatched embryos grown in vitro for 15 days and (3) trophoblast cells derived from cells dispersed from placentae collected between Days 31 and 39 of pregnancy. A specific radioimmunoassay was used to detect concentrations of baboon CG in daily spent medium. Immunohistochemical studies showed that material cross-reacting with CG was present on all the three sources of trophoblast. The embryos secreted CG from attachment onwards and immunoactive CG was measurable in daily spent medium collected from placenta-derived trophoblast cultures. It is concluded that baboon CG is localized in the syncytiotrophoblast of fixed placental sections and cellular trophoblast derived from cultured embryos and placental cells.
Keywords: baboon; trophoblast; chorionic gonadotrophin; immunochemistry
C. S. Bambra, S. S. Lynch, G. R. Foxcroft, G. Robinson and E. C. Amoroso
Summary. A human chorionic gonadotrophin-like protein (GF-1, 1·0 g) from the placentae of 50 guinea-pigs killed at Day 26 of gestation was purified by pH and ammonium salt fractionation followed by column chromatography on DEAE-Sephadex and filtration on Sephadex G-100. Relative to the Second International hCG standard (MRC 61/6) GF-1 had an immunological potency of 21 000 i.u./mg as measured in a specific hCG-β radioimmunoassay and, using the ovarian ascorbic acid depletion assay, an apparent biological potency of 24 064 i.u./mg. Isoelectric focussing yielded 6 bands between pH 4·4 and 5·7 and the material comprised two non-covalently linked subunits. The Stokes' radii were 3·40 nm for the native preparation, and 2·38 nm and 3·15 nm for GF-1-α and GF-1-β subunits respectively. The guinea-pig placenta therefore produces a chorionic gonadotrophin which on purification has physicochemical, biological and immunological properties similar to those of hCG.