The Hormone Exocytosis in Prolactinoma and Normal Adenohypophysis Cell Cultures by the Effects of Hypocalcaemia

The biological systems are opened, complex objects, which can regularly exchange feedbacks with their environment. The calcium ion is a universal messenger, which can regulate several cellular functions e.g. exocytosis machinery. The primary aim of this study was to investigate the response mechanisms of normal adenohypophysis and adenohypophyseal prolactinoma cell populations at different extracellular Ca2+ levels with an otherwise isoionic milieu of all other essential ions. We focused on prolactin (PRL) and adrenocorticotrophic hormone (ACTH) release. In our experimental study, female Wistar rats (n=10) were treated with estrone-acetate (150 μg/kg b.w/week) for 6 months to induce prolactinomas in the adenohypophysis. Primary, monolayer cell cultures were prepared by enzymatic and mechanical digestion. PRL and ACTH hormone presence was measured by radioimmunoassay or immuno- chemiluminescence assay. Repeated measurements of ACTH and PRL hormone release in different treatment groups on cell cultures during 80 minutes were compared using marginal models. Differences between the effects of hypocalcaemia on normal adenohypophysis cultures and prolactinoma cell populations were investigated. Significant alteration (p<0.001, n=12) in hormone exocytosis was detected in Ca2+ treated adenohypophyseal and prolactinoma cell cultures, compared to untreated groups. Diminution of Ca2+ may inhibit the SNARE mediated fusion of hormone containing vesicles to plasma membrane. In conclusion, the main finding of this study is that a strict correlation exists among certain biophysical properties, especially extracellular Ca2+ milieu and hormone vesicle exocytosis.