Membrane functions in tumorous cells are different from those in healthy cells. The aim of the present study was to investigate the changes in pituitary cell membrane functions and
hormone secretion after
tumor induction in vivo and in vitro.
Prolactinomas were induced in vivo in female Wistar rats with
estrone acetate. Normal anterior pituitaries and
prolactinomas of female Wistar rats were dissociated enzymatically and mechanically, then cultured on
collagen-treated
plastic dishes. Some normal anterior pituitary cultures were treated with benz(c)
acridines as tumorigenic agents in vitro. Intracellular 3',5'-cyclic-adenosine monophosphate (cAMP) levels were determined by a competitive binding technique, membrane fluidity was assayed by fluorescence anisotropy, and
ATP-ase activities were estimated via
ATP loss. The results indicated decreased membrane fluidity in tumorous cell cultures. However, in vitro
benz(c)acridine treatment exerted more pronounced effects than those observed after in vivo
estrone treatment. The
ATP-ase activities were highly increased in
benz(c)acridine-treated cells and in
estrogen-induced
prolactinoma cells, more strongly so in the former ones. The intracellular cAMP levels were higher than normal in both of them. The results concerning the
ACTH,
alpha-MSH, PRL and GH levels of normal and tumorous cell cultures were published in our previous study. Our findings show that the tumorous transformation of pituitary cells can cause significant changes in functional membrane parameters and
hormone secretion. Decreased membrane fluidity was accompanied by an increased exocytosis (
hormone release) and
adenylate cyclase activity in tumorous cells.