. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 288 M. MITA ET AL Table II Lipid metabolism in a cell-tree system oj Arbacia lixula spermatozoa Content (Mg/mg protein) Lipids Contro 1 Incubation for 1 h PC 39 ±. ! 39 ± 2 PS 20 ± 21 ± 1 PE 28 ± 29 ±2 DPG 16 ± 16 ± 1 Ch 24 ± 24 ± 1 FFA 3 ± 7+1" TG 11 ± 7 ± la The homogenate of dry sperm with 10 MgCl:. 10 mlM MgCl:, I dithiothreitol. and 50 Tris-HCl at pH was incubated for 1 h at 20°C. Each value is the mean ± SEM obtained from three separate experiments. I' \alues are comparisons with the control. "
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 288 M. MITA ET AL Table II Lipid metabolism in a cell-tree system oj Arbacia lixula spermatozoa Content (Mg/mg protein) Lipids Contro 1 Incubation for 1 h PC 39 ±. ! 39 ± 2 PS 20 ± 21 ± 1 PE 28 ± 29 ±2 DPG 16 ± 16 ± 1 Ch 24 ± 24 ± 1 FFA 3 ± 7+1" TG 11 ± 7 ± la The homogenate of dry sperm with 10 MgCl:. 10 mlM MgCl:, I dithiothreitol. and 50 Tris-HCl at pH was incubated for 1 h at 20°C. Each value is the mean ± SEM obtained from three separate experiments. I' \alues are comparisons with the control. "P < ; T also observed during incubation. The FFA and lysophos- phatidylcholine (Lyso PC) contents increased remarkably (P < ). However, PS. DPG, and Ch levels did not change significantly. A trace amount of TG was present in P. lividus spermatozoa. Phospholipase ami lipase activities When the homogenate of dry sperm from A. lixula was incubated with [carboxyl-'4C]triolein for 1 h at 20°C. the radioactivity was transferred from TG to FFA (Table IV). Lipase activity was found in A. lixula spermatozoa; how- ever, incubation with l-palmitoyl-2-[l-'4C]arachidonyl- PC or l-palmitoyl-2-[l-MC]arachidonyl-PE showed that Table IV Activities of lipase and phospholipase A: in Arbacia lixula and Paracentrotus lividus spermatozoa Activity (nmol FFA released/h/ mg protein) Substrate A. I/Mild P lividus PC 0. 1 ± 0. 1 ± PE tr. ± TG ± tr. Each value is the mean ± SEM obtained from three separate experi- ments, trace amount (less than nmol FFA released/h/mg protein). only a little radioactivity was transferred to FFA by the action of phospholipase A:. In the case of P. lividus sper- matozoa, phospholipase A: activity was high, although lipase activity was extremely low (Table IV). The hydrol- ysis of PE was about one third that of PC. Phospholipase A2 in P. lividus spermatozoa thus appears to have greater substrate specificity
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