Surface changes and hormone production in pituitary cells during tumorigenesis

Prolactinomas were induced by chronic estrone acetate treatment in female W istar rats in vivo. After enzymatic dissociation of the tumor tissue, monol ayer cell cultures were obtained. In vitro tumor induction was performed by treatment of normal monolayer anterior pituitary cell cultures with a 1:1 mixture of 7,9-dimethylbenz[c]acridine: 8-methylbenz[c]acridine. For immuno histochemistry, the cell cultures were stained by the peroxidase-antiperoxi dase method for standardization; the nonspecific hormone release was induce d with 30 mM K+. The prolactin, alpha-melanotropin, and adrenocorticotropin levels in the supernatant were measured by specific, sensitive radioimmuno assays. The results indicated surface differences between the in vivo induced prola ctinoma cells and normal pituitary cells: the attachment of the prolactinom a cells required 15% collagen treatment, whereas normal cells required only 3-4% collagen. Tumor cells induced in vitro by methylbenz[c]acridine treat ment were able to attach only after ammonia activation of the collagen surf ace. These findings strongly suggest that the mode of tumor induction can r esult in differences in membrane fluidity; this phenomenon is possibly conn ected with the levels of prolactin, adrenocorticotropin and alpha-melanotro pin hormone production of these endocrine tumor cells.