Radioreceptor assay for lactogenic hormones based on membranes from rat mammary tumour.

A highly sensitive radioreceptor assay (RRA) for human prolactin (hPRL) based on membrane preparations obtained from chemically induced rat mammary tumour is described. The binding of 125I-labelled, highly purified pituitary human prolactin was specific for lactogenic hormones and depending on time, temperature, and concentration of receptor protein. Optimal specific receptor binding (18-20%) was obtained by incubation at 21 degrees C for 18 h.

Polymorphism of human pituitary lutropin (LH). Effect of the seven isohormones on mouse Leydig cell functions.

The effect of the 7 different molecular forms of human pituitary lutropin (LH) on mouse Leydig cells as a model of a target organ were studied. The hormone functions have been characterized by receptor binding, cAMP accumulation and testosterone production. One important finding was the similar intrinsic in vitro biological activity for all isohormones.

Polymorphism of human pituitary lutropin (LH). Isolation and partial characterization of seven isohormones.

The complete microheterogeneous system of human pituitary lutropin was demonstrated by gel isoelectric focusing. In addition 7 LH isohormones could be isolated by preparative column focusing and characterized with respect to physicochemical, biological and immunological properties. The in vivo biopotencies ranged from 4.

Biological and immunological potencies of lutropin (LH) in human serum: comparative studies using different standard preparations.

The mouse leydig cell in vitro-bioassay for LH, first reported by van Damme, Robertson and Diczfalusy (1974) was modified and applied to female and male serum. Non-parallelism of dose-response curves between serial dilutions of individual male as well as female sera and LH standards was caused by damage to incubated interstitial cells in the presence of human serum. The extent of cell damage- paralleled by an inhibition of testosterone production - was a characteristic of individual human sera rather than a general protein effect.

Isolation of highly purified sex hormone binding globulin (SHBG): evidence for microheterogeneity.

Highly purified sex hormone binding globulin (SHBG) was isolated in milligram amounts from a human serum fraction (Cohn IV-4). The final preparation was homogeneous by the criteria of polyacrylamide-gel electrophoresis. Immunological evidence for purity could be given by double diffusion according to Ouchterlony.