Hokin M R, Hokin L E
J Gen Physiol. 1967 Mar;50(4):793-811. doi: 10.1085/jgp.50.4.793.
Acetylcholine, which stimulates NaCl secretion in the avian salt gland, causes the rapid formation of a fraction of phosphatidic acid, as measured by (32)P incorporation, which amounts maximally to about 0.18 micromoles per g of fresh tissue. This does not appear to involve synthesis of the diglyceride moiety of phosphatidic acid, as measured by glycerol-1-(14)C incorporation. It presumably involves formation of phosphatidic acid by the diglyceride kinase pathway from preformed diglyceride and ATP. The specific activity of the AT(32)P of the tissue is not increased in the presence of acetylcholine. At time intervals after addition of acetylcholine during which a full response, measured as increased O(2) uptake, may be observed, phosphatidic acid appears to be the only phosphatide which shows any increase either in total (32)P radioactivity or in net specific acitvity. This responsive fraction of phosphatidic acid undergoes continuous turnover of its phosphate moiety. There is no evidence that this turnover is due to the phosphatidic acid acting as a pool of intermediate for the synthesis of other phospholipids or glycerides. The responsive fraction amounts to not more than 20% of the total phosphatidic acid of the tissue; it does not mix with the other (non-responsive) phosphatidic acid of the tissue. The observations suggest that this phosphatidic acid plays some role in the over-all secretory process.
乙酰胆碱可刺激鸟类盐腺分泌氯化钠，它能促使一小部分磷脂酸迅速形成，这可通过（32）P掺入量来测定，每克新鲜组织中最大量约为0.18微摩尔。通过甘油-1-（14）C掺入量测定表明，这似乎不涉及磷脂酸甘油二酯部分的合成。推测它涉及由预先形成的甘油二酯和ATP通过甘油二酯激酶途径形成磷脂酸。在乙酰胆碱存在下，组织中ATP（32）P的比活性并未增加。在加入乙酰胆碱后的时间间隔内，在此期间可能观察到以氧气摄取增加来衡量的完全反应，磷脂酸似乎是唯一一种无论是总（32）P放射性还是净比活性都有所增加的磷脂。磷脂酸的这一反应部分经历其磷酸部分的持续周转。没有证据表明这种周转是由于磷脂酸作为合成其他磷脂或甘油酯的中间物池所致。反应部分不超过组织总磷脂酸的20%；它不与组织中的其他（无反应的）磷脂酸混合。这些观察结果表明，这种磷脂酸在整个分泌过程中发挥着某种作用。
