| Summary: | 碩士 === 國立臺灣大學 === 動物學研究所 === 97 === Lysophospholipids（LPLs）, including lysophosphatidic acid（LPA） and sphingosine 1-phosphate（S1P）, are lipid derivatives with versatile cell functions. Our previous results have shown that LPLs attenuated the Ca2+ currents in bovine chromaffin cells. In this report, we are focused on their effects on Ca2+-activated K+ （BK）channels and exo/endocytosis. Using specific primers against BK channel alternative-splicing isoforms, four isoforms were identified using RT-PCR. Chromaffin cells were voltage-clamp in perforated patch configuration and the outward K+ currents at +80 mV were recorded. 54.1 ± 5.3% of the outward current was inhibited by BK channel specific inhibitor, iberiotoxin. The toxin sensitive currents were reduced to 27.7 ± 10.7 and 26.3 ± 7.6% of the total outward current by S1P and LPA treatment, respectively. By patching the cell in whole-cell mode, increasing Ca2+ buffering capacity affected BK current amplitude, but not the ratio to total current. However, BK evoked by elevating the [Ca2+]i to 1 μM was not affected by S1P treatment. To characterize the roles of LPLs on exo/endocytosis, cells were voltage-clamped in perforated patch mode and the membrane capacitance was recorded to reflect the changes in the exo/endocytosis. To monitor the release kinetics from each secretary vesicle, voltammetry was applied. The results showed that LPL treatment sharpens the spikes and reduces spike area, indicating that LPLs decrease vesicle quantal content. The distribution of clathrin at the subplasmalemma region was less in LPL treated groups. These results suggest that LPLs indirectly modulate BK channel activity by attenuating the Ca2+ currents and modify the exo/endocytosis kinetics.
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