STIMULATION OF GROWTH HORMONE RELEASE FROM SUPERFUSED RAT PITUITARY BY EXTRACTS OF HYPOTHALAMUS AND OF HUMAN LUNG TUMOURS

Abstract

SUMMARY The paradoxical plasma growth hormone (GH) responses to oral glucose in certain patients with lung cancer prompted an examination of tumour extracts for GH releasing activity. Exposure of superfused rat pituitary to pulses (30 s) of aminophylline and to extracts from rat, sheep and human hypothalami resulted in a rapid and short-lived release of immunoreactive rat GH into the medium. Fresh extracts from five lung tumours, and from the surrounding lung tissue of four of these tumours significantly stimulated the release of GH, while extracts of a metastatic chondrosarcoma and normal rat lung were inactive. Gel filtration experiments suggested that the releasing activity in rat, sheep and human hypothalamic tissue and in human lung tumour extracts was present in at least two molecular species of different sizes.