Prostaglandins in rainbow trout (Oncorhynchus mykiss Walbaum, 1792) sperm biology – searching for answers

The purpose of this study was to determine the concentrations of prostaglandins E₂ and F_2α (PGE₂ and PGF_2α) in the blood, testis and seminal plasma of mature male rainbow trout and in the ovarian fluid to assess the effects of these prostaglandins on sperm motility parameters when present in activation media. Also prolonged incubation with prostaglandins on sperm motility and calcium influx were studied. The profile of PGE₂ and PGF_2α differed in concentration between blood, testicular supernatant and seminal plasma. PGE₂ was predominant in the blood sample (0.29 ng ml^?1) and testicular supernatant (3.1 ng ml^?1) whereas their level in seminal plasma was lower than PGF_2α (0.23 ng ml^?1). The concentrations of PGF_2α in blood, testis and seminal plasma were 0.04, 0.99, 1.3 ng ml^?1, respectively. In the ovarian fluid the concentrations of both prostaglandins were higher than in the male reproductive tract. Adding both prostaglandins to activation buffer (at concentrations 15 and 70 ng ml^?1) had no effect on any CASA parameters. Calcium influx related to rainbow trout sperm incubations with PGE₂, and PGF_2α was not detected. After 24 h incubation of sperm in artificial seminal plasma solution without and with prostaglandins all sperm samples increased their motility potential and intracellular calcium concentration. Therefore, this effect was not related to the presence of prostaglandins. In summary PGE₂, and PGF_2α were present in the rainbow trout male reproductive tract, and their profile varies from that of blood, testis and seminal plasma. The specific role of both prostaglandins in salmonid sperm biology remains unclear.