Somatocrinin (growth hormone releasing factor) in vitro bioactivity; Ca++ involvement, cAMP mediated action and additivity of effect with PGE2 |
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Authors: | Paul Brazeau Nicholas Ling Frederick Esch Peter Böhlen Christiane Mougin Roger Guillemin |
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Institution: | Laboratories for Neuroendocrinology The Salk Institute for Biological Studies La Jolla, Ca 92037 USA |
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Abstract: | The release of GH induced by purified hypothalamic GRF or native or synthetic tumor-derived GRF is antagonized by the presence of CoCl2; it is simulated by 8Br .cAMP, IBMX, cholera toxin, forskolin, with identical maximal effects (Emax). Somatocrinin (GRF) stimulates the efflux of cAMP by the pituitary cells in parallel to the release of GH. Addition of either 8Br .cAMP, IBMX, cholera toxin or forskolin to a maximally stimulating dose of GRF does not increase the response which remains GRF-Emax. In contradistinction with these results PGE2 releases GH with a dose-response curve different from that of GRF, and the combination of PGE2 + GRF produces an Emax far greater than that due to either agonist alone; showing a true additivity. The name is proposed to replace the acronym GRF. |
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