Arsenic reduces prolactin secretion and induces cell death in anterior pituitary cells

SA RONCHETTI, FA QUINTEROS, JP CABILLA, ME GONSEBATT, BH DUVILANSKI

San Diego

Congreso; 92ND Annual Meeting Endocrine Society; 2010

Endocrine Society

Arsenic (As) is one of the most environmental toxic metals. Inorganic arsenic exposure via drinking water has been associated with cancer and serious damage to various internal organs. However, its effects on endocrine function have not been clearly established yet. In the present study we have investigated the effect of As on anterior pituitary cell physiology. We examined the effect of As3+ (sodium arsenite) on prolactin (PRL) release (by radioimmunoassay) and on cellular viability (by MTT assay) in primary cultures of pituitary cells from adult male Wistar rats. Caspase-3 activation was also evaluated by a Ac-DEVD-pNA colorimetric assay. Cells exposed to As3+ for 24 h showed a decrease of PRL release in a dose-dependent way ([PRL] as % of control, As 1 M: 55.5 8.9*; As 10 M: 17.2 3.9**; As 25 M: 12.4 3.**; *p< 0.05, **p<0.01 vs. control). As3+, only at 25 M decreased cellular activity after 24 h of exposure (Abs 600nm, as % of control; 1 M: 111.5 5.5; 10 M: 119.5 8.9; 25 M: 63.2 8*; *p<0.05 vs. control). As3+ (25 M) induced a decrease in PRL release (measured after 24 h of incubation) in a time-dependent manner although a slight increase was initially observed. In the same experiment, the cytotoxic effect of the metal was not evident at 1, 3 or 6 h of incubation but became irreversible at 9 h (Abs 600nm, as % of respective control; 9h: 73.9 4.1**, 12h: 71.6 2.9***, 24h: 54.8 4.6***; **p<0.01; ***p<0.001 vs. respective control). Additionally, 25 M As3+ induced caspase 3 activation (sample Abs 405nm x mg of protein x 100/control Abs 405nm x mg of protein, As 6 h: 110.9 9.3; As 9 h: 345 103*; *p<0.001 vs. control). The cytotoxic effect of the metal was confirmed by immunocytochemistry (acridine orange-ethidium bromide) assay in which an increased number of nuclei with necrotic and apoptotic morphology was observed. Our results show, for the first time, that As3+ affects pituitary physiology by reducing both PRL release and cell viability in vitro. The decrease of hormone release could be an early event of the toxic effect of the metal.