ATP-induced apoptosis of human granulosa luteal cells cultured in vitro.

Objective: To investigate the role of extracellular adenosine triphosphatase (ATP) as an inducer of apoptotic cell death in human granulosa cells and to elucidate its underlying mechanism.

Design: Prospective study.

Setting: Gynecologic clinic and human reproduction research laboratory.

Patient(s): Twenty-five patients undergoing IVF or IVF-ET.

Intervention(s): ATP treatment of granulosa luteal cells subjected to primary culture.

Main Outcome Measure(s): Apoptosis was assessed by the annexin V binding assay and the terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick-end labeling assay. The receptor type that binds ATP, thus mediating ATP-induced apoptosis, was determined by using the calcium imaging and patch-clamp techniques. Mitochondrial depolarization was assessed by staining with the membrane potential-sensitive dye 5,5',6,6'-tetrachloro-1,1',3,3'- tetraethylbenzimidazolyl carbocyanide iodide (JC-1).

Result(s): ATP elevated [Ca(2+)](i) by mobilizing intracellularly stored Ca(2+). An ionic membrane current evoked by ATP was mediated by the Ca(2+)-activated K(+) channel. ATP induced a mitochondrial depolarization with a concomitant increase in cellular apoptosis. Treatment with hCG eliminated both ATP-induced mitochondrial depolarization and apoptosis.

Conclusion(s): Extracellular ATP recognized by P(2Y) type purinoceptor triggers apoptosis in human granulosa luteal cells, and the downstream apoptotic cascade may act at least in part through mitochondria. The antiapoptotic effect of hCG has possible clinical implications in the treatment of disorders involving granulosa cell degeneration (such as follicular atresia).