The chemotactic activity of various sirenins and analogues and the uptake of sirenin by the sperm of allomyces.

The enantiomorphs of sirenin and several analogues of sirenin were tested for their activity in attracting the sperm of Allomyces. Only l-sirenin was active. The uptake of sirenin by the sperm was measured from solutions containing l-sirenin in concentrations from 5 to 10,000 nm. Uptake from 5 and 100 nm followed first order kinetics. At higher concentrations the rate of uptake slowed down, and at the very highest ones it stopped after a few minutes. When sperm had taken up all the sirenin from a 5 nm solution, it took approximately 45 minutes for them to regain full responsiveness. After uptake of sirenin by sperm, none could be recovered from them.