Determination of human sperm calcium uptake mediated by progesterone may be useful for evaluating unexplained sterility.

Sperm samples from couples who underwent assisted reproduction were classified according to the World Health Organization (WHO) criteria of concentration, motility, and morphology, in normal and subnormal cases (oligozoospermic, asthenozoospermic, and teratozoospermic). The percentage of spermatozoa that increased [Ca(2+)](i) in response to progesterone (P) was determined by means of flow cytometry. The evaluation of the P-mediated intracellular calcium increase by flow cytometry may be a fast and objective tool for the diagnosis of human sperm samples, especially in cases of unexplained sterility.