Characterization of solubilized prolactin receptors from Rana catesbeiana tadpole tissues

Prolactin (PRL) receptors were solubilized from Rana catesbeiana tadpole liver and tail fin and female Sprague-Dawley rat-liver membranes by treatment with 1% Triton X-100. Binding of [125I]oPRL to tadpole-liver and tail-fin solubilized extracts reached equilibrium by 12 h at 19 degrees C. The binding was linear up to 50 micrograms of tadpole liver and tail-fin protein and 30-40 micrograms of rat-liver protein. Solubilization did not affect the dissociation constant for [125I]oPRL binding but did result in a greater number of sites. The binding was specific for oPRL and hGH, which has PRL-like activity. Neuraminidase pretreatment of membranes altered the binding affinity of oPRL to tadpole-liver membranes and solubilized extracts but not to tadpole-tail fin membranes or extracts. Pretreatment of membranes with neuraminidase did not affect the binding capacity of tadpole-liver or tail-fin membranes or solubilized extracts.