Ollivier-Bousquet M, Lacroix M C
Reprod Nutr Dev (1980). 1986;26(2B):575-82.
Phospholipase A2 and arachidonic acid mimic the stimulatory effect of prolactin on casein exocytosis. We suggest that prolactin by activating phospholipase A2, induces a release of arachidonic acid which is metabolized by a cyclooxygenase pathway leading to prostaglandins, prostacyclins and thromboxanes, a lipoxygenase pathway leading to hydroperoxides and leukotrienes and an epoxygenase pathway. The effects of prolactin and of the major products of arachidonic acid metabolism were studied by incubating mammary gland fragments of lactating rabbit and by measuring neosynthesized caseins and prostaglandins F (PGF2 alpha) in the incubation medium. Aspirin (10(-3) M) which strongly decreases PGF2 alpha synthesis did not modify exocytosis or prolactin stimulation of exocytosis. However, in some cases where prolactin did not stimulate exocytosis, aspirin could restore this stimulation. Nor-dihydroguaiaretic acid (10 microM), an inhibitor of lipoxygenases, increased PGF2 alpha synthesis in the presence of prolactin. In parallel, this inhibitor increased casein exocytosis but inhibited prolactin stimulation. These results are consistent with the action of arachidonic acid metabolites in the regulation of casein exocytosis. We suggest a dual control by the metabolites of the lipoxygenase and the cyclooxygenase pathways.
磷脂酶A2和花生四烯酸模拟催乳素对酪蛋白胞吐作用的刺激效应。我们认为，催乳素通过激活磷脂酶A2，诱导花生四烯酸释放，花生四烯酸经环氧化酶途径代谢生成前列腺素、前列环素和血栓素，经脂氧合酶途径代谢生成氢过氧化物和白三烯，还经环氧合酶途径代谢。通过孵育泌乳兔的乳腺片段，并测量孵育培养基中新合成的酪蛋白和前列腺素F（PGF2α），研究了催乳素和花生四烯酸代谢主要产物的作用。强烈降低PGF2α合成的阿司匹林（10^(-3) M）并未改变胞吐作用或催乳素对胞吐作用的刺激。然而，在某些催乳素未刺激胞吐作用的情况下，阿司匹林可恢复这种刺激。脂氧合酶抑制剂去甲二氢愈创木酸（10 μM）在有催乳素存在时增加了PGF2α的合成。同时，该抑制剂增加了酪蛋白胞吐作用，但抑制了催乳素的刺激。这些结果与花生四烯酸代谢产物在酪蛋白胞吐作用调节中的作用一致。我们提出脂氧合酶和环氧化酶途径的代谢产物存在双重调控作用。
