Pituitary adenomas: patterns of hPRL and hGH secretion as revealed by high resolution immunocytochemistry

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Abstract
Seven human pituitary adenomas obtained by transphenoidal surgery were investigated for the intracellular localization of PRL [prolactin] and GH [growth hormone], using the protein A-gold immunocytochemical technique. Among the 7 cases 2 were prolactinomas, 2 were GH-secreting adenomas and 3 were mixed PRL and GH-secreting adenomas. When PRL or GH were revealed, immunoreactivity was found in the cellular compartments involved in protein secretion, RER [rough endoplasmic reticulum], Golgi apparatus and secretory granules of corresponding secreting cells. An increasing gradient in the intensity of labeling as observed from the RER to the Golgi and to the granules which may correspond to the increasing concentration of the proteins occurring along their secretory pathway. Crinophagy or destruction of secretory granules by the lysosomal system was observed for both secretory cells. Cells displaying simultaneously PRL and GH reactivity were never found, neither in pure nor in mixed adenomas demonstrating that in the different adenomas studied, secreting cells have retained their specificity and differentiation for the secretion of a single hormone.