Progesterone at the picomolar range is a chemoattractant for mammalian spermatozoa

TEVES, ME; BARBANO, F; GUIDOBALDI, HA; UÑATES, DR; SANCHEZ, R; MISKA, W; ROVASIO, RA; GIOJALAS, LC

Giessen, Alemania

Workshop; 4th International Workshop "Molecular Andrology"; 2005

Sperm chemotaxis is a cell transport mechanism that guides spermatozoa up an attractant concentration gradient in order to facilitate the gamete encounter. Sperm chemotaxis was observed towards: follicular fluid (in humans, mice and rabbits), oviductal fluid (in mice), and the egg-cumulus complex (in humans and rabbits). Progesterone (P), the main steroid of the mentioned biological sources, has been assayed for human sperm chemotaxis by different groups, giving rise to contradictory results. The aim of this work was to examine whether sperm chemotaxis is mediated by progesterone at extremely low concentrations that were not investigated before. Human and rabbit capacitated spermatozoa were confronted with several progesterone concentrations (1 pM to 1 mM) in a chemotaxis chamber, studying the sperm kinematic behavior with a video microscopy system and a computer image analysis. Relative fluorescence intensity along the egg-cumulus complex was measured as an indicator of a progesterone gradient by confocal immunocytochemistry. Only capacitated spermatozoa showed a chemotactic response towards low (pM) steroid levels with a maximum at 10 pM and 100 pM, for humans and rabbits, respectively. The percentage of hyperactivated spermatozoa significantly increased only at high hormone concentrations (10 uM to 1 mM). A progesterone gradient was detected along the cumulus mass. The results of this work show that progesterone indeed chemotactically guides mammalian spermatozoa at very low hormone concentrations and that the cumulus oophorus could be a potential place for sperm chemotaxis mediated by progesterone in vivo.