Growth hormone-binding sites in chicken hypothalamus

Specific binding of 125I-labelled recombinant DNA-derived chicken GH (rcGH; 2.1 +/- 0.41 (S.E.M.) % of total counts) and of 125I-labelled bovine GH (1.80 +/- 0.27% of total counts) to crude plasma membranes of the chicken hypothalamus was demonstrated. Binding of 125I-labelled rcGH was related to the amount of tissue incubated and was significant over the range 250-950 micrograms membrane protein per tube. Binding of 125I-labelled rcGH was saturable over the range 0.14-0.40 pmol and was to a single class of high-affinity (33.5 pM) low-capacity (2.14 fmol/mg protein) binding site. Binding of 125I-labelled rcGH was displaced by ovine GH and by ovine prolactin. These results demonstrate, for the first time, central GH-binding sites in a vertebrate species.