Sadler K, Litosch I, Fain J N
Biochem J. 1984 Sep 1;222(2):327-34. doi: 10.1042/bj2220327.
Blowfly salivary glands, previously exposed to 10 microM-5-hydroxytryptamine for 30 min, demonstrated a rapid compensatory resynthesis of [3H]inositol-labelled phosphatidylinositol 4,5-bisphosphate when allowed to recover in medium containing 3-5 microM-inositol. Phosphatidylinositol 4,5-bisphosphate comprised 70% of the total [3H]-phosphoinositide, and there was a corresponding decrease in the formation of [3H]-phosphatidylinositol. Subsequent addition of 5-hydroxytryptamine produced an equivalent breakdown of the newly synthesized phosphoinositides but little 45Ca2+ gating. Increasing the inositol concentration in the medium to 300 microM produced a 14-fold stimulation of phosphatidylinositol synthesis but only a 5-fold increase in phosphatidylinositol 4,5-bisphosphate synthesis. Increasing the inositol concentration in the medium from 3 microM to 300 microM resulted in a progressively greater recovery of the 45Ca2+-gating response. At 300 microM-inositol there was an 85% recovery of 45Ca2+-gating response. These results indicate that conversion of phosphatidylinositol into phosphatidylinositol 4,5-bisphosphate occurs in blowfly salivary glands and is secondary to an initial breakdown of the phosphoinositides. Recovery of Ca2+ gating is dependent on the restoration of both phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate to appropriate concentrations.
先前在10微摩尔 - 5 - 羟色胺中暴露30分钟的绿头苍蝇唾液腺，当在含有3 - 5微摩尔肌醇的培养基中恢复时，显示出[3H] - 肌醇标记的磷脂酰肌醇4,5 - 二磷酸的快速代偿性再合成。磷脂酰肌醇4,5 - 二磷酸占总[3H] - 磷酸肌醇的70%，并且[3H] - 磷脂酰肌醇的形成相应减少。随后添加5 - 羟色胺会使新合成的磷酸肌醇产生等量的分解，但几乎没有45Ca2 +门控作用。将培养基中的肌醇浓度增加到300微摩尔会使磷脂酰肌醇合成受到14倍的刺激，但磷脂酰肌醇4,5 - 二磷酸合成仅增加5倍。将培养基中的肌醇浓度从3微摩尔增加到300微摩尔会导致45Ca2 +门控反应的恢复逐渐增加。在300微摩尔肌醇时，45Ca2 +门控反应有85%的恢复。这些结果表明，磷脂酰肌醇向磷脂酰肌醇4,5 - 二磷酸的转化发生在绿头苍蝇唾液腺中，并且是磷酸肌醇最初分解的继发结果。Ca2 +门控的恢复取决于磷脂酰肌醇和磷脂酰肌醇4,5 - 二磷酸都恢复到适当的浓度。
