Attenuation of growth hormone gene expression in desensitized somatotropes

The effects of GRF-induced desensitization of somatotropes on GH gene expression were investigated on pituitary cells derived from male rats. Pretreatment of monodispersed cells for 18 hr with GRF abolished both the acute release of GH and the stimulation of GH gene expression in response to a subsequent 4 hr challenge with GRF. Concomitant preincubation with GRF and SS resulted in restoration of the ability of GRF to stimulate release of GH but not to augment GH gene expression. These results demonstrate that desensitization by GRF affects both the release of GH and GH gene expression, whereas the resensitizing effects of SS appear to be directed exclusively at the release mechanism.