Immunoreactive growth hormone-releasing factor in human stalk median eminence

Immunoreactive growth hormone-releasing factor was detected in extracts of acetone preserved human stalk median eminence utilizing an antiserum against human GRF-(1-44)-NH2, isolated from a pancreatic tumor. The antibody is highly specific for the C-terminus of GRF-(1-44)-NH2, and has a cross-reactivity less than 0.02% with GRF-(1-40) free acid, a peptide isolated from a different pancreatic tumor. The mean concentration of IR-GRF in 5 pools of 10-15 stalk-median eminence fragments was 57.7 +/- 7.2 ng/mg protein (mean +/- SEM, range 42.5-75.8 ng/mg protein). Gel filtration chromatographic analysis showed that 97% of the IR-GRF coeluted with synthetic hpGRF-(1-44)-NH2 and eluate inhibition of binding in the radioimmunoassay was parallel to that of hpGRF-(1-44)-NH2. These data strongly suggest that human hypothalamic tissue contains a peptide that is similar to hpGRF-(1-44)-NH2.