Meeting Abstract
P2.98 Jan. 5 Spontaneous sea urchin sperm activation, a basic matter? Sperm activating peptides, pH, and motility. CORTEZ, A*; VUONG, L; CARDULLO, RA; Univ. of California, Riverside; Univ. of California, Riverside; Univ. of California, Riverside alejandro.cortez@email.ucr.edu
The binding of egg-derived sperm activating peptides to receptors on sea urchin sperm flagellum increase motility through a pathway that involves changes in intracellular pH. Extracellular changes in pH influence internal pH, and hence motility. We quantified motility in a spectrophotometer using various sperm activating peptides at different pH conditions. Speract, a decapeptide, has been shown activate sperm motility in several species closely related to Strongylocentrotus purpuratus. Lytechinus pictus (15 x 106 sperm/mL) sperm were layered at the bottom the test solution using 10% ficoll. Changes in optical density (OD) at 545 nm were used to quantify sperm concentrations at fixed times above the ficoll layer to estimate velocities under different conditions. ASW was adjusted to the desired pH and supplemented with different concentrations of the decapeptides. It has been previously reported that at pH 6.6, sperm motility is suppressed and speract binding results in increases in cellular respiration and motility. In our assay, 100 nM speract led to a rapid increase in optical density followed by a sharp decline. At the physiological pH of 8.0, sperm were spontaneously activated and 100 pM speract resulted in an increase in OD that was maintained for long periods of time. The effect of pH on sperm motility, ranging from pH 5.8-8.2, was assayed at a fixed concentration of 100 pM speract. The results from this assay are consistent with previous findings on the effects of speract and pH on sperm motility and provides a convenient method for monitoring the role of related sperm activating peptides (coded in the same gene) and other modulators of flagellar motility. Furthermore, this assay can be employed to carryout comparative studies among species known to respond to speract.
