DISCORDANCE OF PROLACTIN GENE-TRANSCRIPTION, MESSENGER-RNA STORAGE, AND HORMONE-RELEASE IN INDIVIDUAL MAMMOTROPES

The mammotrope has traditionally been a favored model for studies of h ormonal gene expression, biosynthesis, and release. However, the prima ry site(s) at which these processes are coordinated and integrated rem ains to be established. Because there is considerable indirect evidenc e to suggest that the rate of prolactin (PRL) secretion is dictated, i n large part, at the level of transcription, the relative contribution of other putative regulatory foci has received less attention. The pu rpose of the present study was to test the primacy of transcriptional regulation at the single-cell level. To this end, we quantified within individual mammotropes the relationship between PRL gene transcriptio n, mRNA storage, and hormone release. This was accomplished by the com bined application of ''real-time'' measurement of gene expression, in situ hybridization cytochemistry, and reverse hemolytic plaque assay, respectively. Our results demonstrate a quantitative dissociation amon g these variables, suggesting that control mechanisms besides transcri ption play a primary role in integrating and coordinating flow through the PRL secretory pathway.