[GRF and human somatotropic adenoma. In vivo and in vitro correlations between GH release and morphological and immunocytochemical aspects]

Nine somatotropic adenomas identified by histological and immunocytochemical methods were studied in vitro during 40 days. The spontaneous release of GH decreased at various rates according to adenomas. A decrease in the size, number of secretory granules and in immunoreactivity with anti-hGH serum were also noted. When cortisol was added (350 nM), the GH secretion sustained for a longer time or even increased at its initial level. The effect of GRF (hpGRF1-44NH2, 10(-8)M) on GH release was tested by 3 hours incubation at 6-9 days of culture. The increase in GH varied from 106 to 420% compared to the basal release. It was similar to in vivo release in 3 out of 6 cases. The highest responses were found in densely granulated and strongly immunoreactive adenomas. The effect of GRF on the GH synthesis was studied by continuous incubation of GRF (10(-8)M) from the 10th the 40th day of culture. The quantity of GH in the culture medium was never higher than in culture mediums without GRF. No change in GH concentrations in mediums with or without cortisol was found when TRH (2.5, 10(-6)M) or TRH + GRF was added. No change in morphological and immunocytochemical cell characteristics were noted either with or without GRF. Thus, the variability of GH response to GRF in somatotropic adenomas in culture seems to be related to their morphofunctional heterogeneity. Under our experimental conditions, GRF stimulates the release of stored GH in tumoral cells but does not seem to stimulate its synthesis.