Relationship of cytoplasmic droplets to motility, migration in mucus, and volume regulation of human spermatozoa.

A significantly greater percentage of motile than immotile spermatozoa bore droplets at the osmolality of semen and cervical mucus. The percentage of spermatozoa with droplets was not significantly correlated with the osmolality of semen or the extent of cell swelling in response to quinine in hypotonic medium. Droplets appeared slightly more frequently (ie, were more obvious) in the presence of quinine, which blocks regulatory volume decrease, indicating that they are the major site of volume expansion.

Cytoplasmic droplets are normal structures of human sperm but are not well preserved by routine procedures for assessing sperm morphology.

Background: There is a discrepancy between the use of terminology employed by clinicians and basic scientists concerning the cytoplasmic droplets of sperm. Most clinicians consider their presence on sperm to be indicative of abnormal sperm, whereas basic scientists consider them to be attributes of normal sperm.

Methods: The presence of cytoplasmic droplets on human sperm was examined using conventional air-dried, fixed and stained sperm smears and in living and fixed wet preparations.