维甲酸对人肝癌细胞磷脂酰胆碱专一性磷脂酶D的作用

为了解细胞信号转导与细胞分化间的关系，研究了诱导分化剂全反式视黄酸（ＡＴＲＡ）和１３顺视黄酸对７７２１人肝癌细胞中磷脂酰胆碱专一性磷脂酶Ｄ（ＰＣ－ＰＬＤ）的影响。发现ＡＴＲＡ和１３ｃｉｓ－ＲＡ除能抑制７７２１细胞生长，并在形态上向正常方向分化外，分别在第２或第４天使膜结合性ＰＣ－ＰＬＤ的比活力升高，用每瓶细胞的总活力计算，ＡＴＲＡ的作用在第２天也高于１３ｃｉｓ－ＲＡ，但１３ｃｉｓ－ＲＡｄ ｔｘ ４

Effect of retinoic acids on phosphatidylcholine specific phospholipase D in 7721 human hepatocarcinoma cell line]

In order to elucidate the relation between cell signal transduction and cell differentiation, the effect of two differentiation inducers--all trans-retinoic acid (ATRA) and 13 cis-retinoic acid (13 cis-RA) on the specific activities (nmol/hr.mg protein) of phosphatidyl choline specific phospholipase D (PC-PLD) in 7721 human hepatocarcinoma cell line was studied. It was found that ATRA and 13 cis-RA increased the specific activities of membrane bound PC-PLD on 2nd and 4th day of cell culture respectively. If the PC-PLD activities were calculated as activity per bottle cells, the effect of ATRA on the 2nd day was also higher than that of 13 cis-RA, while the reverse was true on the 4th day, revealing a postponed effect of 13 cis-RA as compared with ATRA. The increase of PC-PLD was higher when the culture medium was refreshed every day than that when the medium was unrefreshed, suggesting that a factor might be existed in the fresh medium which could enhance the stimulating effect of retinoic acids on PC-PLD. The effect of ATRA on PC-PLD specific activity were higher on 2nd day than that on 4th day, owing to the accelerated proliferation of the cells on 4th day, leading to the increase of protein contents and decrease of the enzyme specific activity calculated on the base of protein contents. Whereas, the effect of 13 cis-RA on PC-PLD specific activity were higher on 4th day than that on 2nd day, because the increase of enzyme activity was higher than the increase of protein contents on 4th day. The relation between the elevation of PC-PLD and protein kinases was further studied and discovered that ATRA decreased both the specific activities of membrane bound and cytosolic protein kinase C (PKC) as well as tyrosine protein kinase (TPK) either in 2nd or 4th day of cell culture, which indicated that the increasing effect of ATRA on membrane bound PC-PLD was not resulted from the stimulating effect of PKC and TPK on PC-PLD, and its mechanism remains to be further investigated.