Khouja A, Jones C T
Laboratory of Cellular and Developmental Physiology, University of Oxford, John Radcliffe Hospital, UK.
J Dev Physiol. 1993 Feb;19(2):61-6.
The release of arachidonic acid and inositol polyphosphates from permeabilised myocytes derived from guinea pig uterus has been studied. Both are enhanced by free calcium at 100 nM and 10 microM and particularly by 50 microM GTP gamma S. To distinguish between the contributions of phospholipase C and A2 to the release of arachidonic acid the phospholipase C inhibitor neomycin was used. At 1 and 10 mM, but not at 0.1 mM, neomycin caused effective inhibition of inositol polyphosphate release of over 95%. Neomycin (1 mM) also reversed GTP gamma S-stimulated, but not calcium-stimulated release of arachidonic acid. This action was reflected in changes in [3H]arachidonic acid labelling of the membrane phosphatidylinositol and phosphatidylcholine pools, which were depressed by over 20% on the addition of 50 microM GTP gamma S, an effect completely reversed by 1 mM neomycin. The effects of neomycin were much more pronounced on inositol phosphate than on arachidonic acid release. The ability of 1 mM neomycin to inhibit arachidonic acid release was reversed by addition of 1 microM phorbol 12-myristate 13-acetate, implying a role for protein kinase C activation in stimulation of arachidonic acid release. Measurement of phospholipase A2 activity with 1-stearoyl 2-arachidonoyl phosphatidylcholine as exogenous substrate demonstrated the ability of 1 and 10 mM neomycin to inhibit the enzyme particularly when it was maximally activated with 1 mM free calcium.(ABSTRACT TRUNCATED AT 250 WORDS)
对豚鼠子宫来源的通透化心肌细胞中花生四烯酸和肌醇多磷酸的释放进行了研究。二者在100 nM和10 μM的游离钙存在时均有所增强，在50 μM GTPγS存在时增强尤为明显。为区分磷脂酶C和A2对花生四烯酸释放的作用，使用了磷脂酶C抑制剂新霉素。在1 mM和10 mM时，而非0.1 mM时，新霉素能有效抑制超过95%的肌醇多磷酸释放。新霉素（1 mM）还能逆转GTPγS刺激的花生四烯酸释放，但不能逆转钙刺激的释放。这一作用反映在膜磷脂酰肌醇和磷脂酰胆碱池中[3H]花生四烯酸标记的变化上，加入50 μM GTPγS时该标记降低超过20%，而1 mM新霉素可完全逆转这一效应。新霉素对肌醇磷酸的作用比对花生四烯酸释放的作用更为显著。加入1 μM佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯可逆转1 mM新霉素抑制花生四烯酸释放的能力，这意味着蛋白激酶C激活在刺激花生四烯酸释放中起作用。以1 - 硬脂酰2 - 花生四烯酰磷脂酰胆碱作为外源底物测量磷脂酶A2活性表明，1 mM和10 mM新霉素能够抑制该酶，尤其是当它被1 mM游离钙最大程度激活时。（摘要截断于250字）
