Interaction of mouse prolactin with mouse hepatic receptors.

Lactogenic receptors are usually studied in heterologous systems where prolactin is derived from one species and receptors prepared from another. In such systems the foreign prolactin could be seen as a growth hormone by the host tissue. We have therefore developed a homologous radioreceptor assay using secreted mouse prolactin (smPRL) and mouse hepatic receptors.

Secreted mouse prolactin (PRL) and stored ovine PRL. I. Biochemical characterization, isolation, and purification of their electrophoretic isoforms.

The biochemical nature of the electroisomers of secreted mouse PRL and stored ovine PRL were compared. When examined on alkaline polyacrylamide gels, they exhibited electrophoretic heterogeneity. The electrophoretic isomers had the same molecular size by examination of Ferguson plots and therefore differed only in net negative charge at alkaline pH.

Secreted mouse prolactin (PRL) and stored ovine PRL. II. Role of amides in receptor binding and immunoreactivity.

Native PRL and des-amido forms 1, 2, and 3 were tested for their individual immunochemical and receptor-binding abilities. The results show that deamidation of either secreted mouse PRL or stored ovine PRL alters their binding in a radioreceptor assay. For each accumulated deamidation there was a statistically significant (P less than 0.

Homologous somatotropin radioreceptor assay utilizing recombinant bovine growth hormone.

A homologous radioreceptor assay using recombinant bovine growth hormone and bovine liver membranes is described. The total specific binding of 125I-labeled recombinant bovine growth hormone to the 100 000 X g pellet was 48% in 24 h at 25 degrees C. Hormone binding was partially reversible, with 40% of the radiolabeled hormone being irreversibly bound.

Protein hormones: detection and extraction of functional forms from alkaline polyacrylamide gels.

A method is presented for rapidly staining zones (30 min) in alkaline polyacrylamide gels in the absence of fixatives. Native functional proteins are recovered in homogeneous form after excision of the visible zones from the polyacrylamide matrix. Removal of dye from excised zones is facilitated because only the surface of the gel is stained.

Isolation, purification, and characterization of mouse placental lactogen.

Mouse placental lactogen was purified 1840-fold from BALB/c placentae from days 14-18 of gestation with an overall yield of 29%. The purification procedure included alkaline homogenization and extraction, ammonium sulfate precipitation, hydrophobic interaction chromatography on Phenyl-Sepharose, ion-exchange chromatography on CM- and DEAE-cellulose, and gel exclusion chromatography on Sephadex G-100. On 10% alkaline polyacrylamide gels, mouse placental lactogen had an Rf of 0.