Biological Effects of an Ectopic Growth Hormone-Releasing Peptide in Cultured Adenohypophyseal Cells: Comparison with Growth Hormone-Releasing Activity of Porcine Hypothalamus*

We have examined the biological effects of a partially purified ectopic GH-releasing peptide (GHRF) in primary monolayer cultures of rat adenohypophyseal cells and compared them with the GH-releasing activity in an acetic acid extract of porcine stalk median eminence (pSME) and with dibutyryl cAMP (DBcAMP). Ectopic GHRF was isolated from a pancreatic islet adenoma and two abdominal carcinoid tumors metastatic to the liver obtained from patients with clinical manifestations of GH hypersecretion. Ectopic GHRF was partially purified by gel filtration chromatography on Sephadex G- 75 or by reverse phase high performance liquid chromatography. The GH-releasing activity of pSME was partially purified by reverse phase high performance liquid chromatography; the two preparations exhibited chromatographic dissimilarities. Both crude ectopic GHRF and pSME stimulated GH release in a dose-dependent manner and exhibited parallel dose-response curves. The potency of ectopic GHRF, however, was 22 times greater than that...