García-Sáinz J A, Alcántara-Hernández R, Robles-Flores M, Torres-Márquez M E, Massillon D, Annabi B, Van de Werve G
Departamento de Bioenergética, Universidad Nacional Autónoma de México, Mexico City.
Biochim Biophys Acta. 1992 Jun 10;1135(2):221-5. doi: 10.1016/0167-4889(92)90140-7.
The effect of phorbol myristate acetate (PMA) on the hormonal responsiveness of hepatocytes from lean and obese Zucker rats was studied. Phenylephrine-stimulated phosphatydylinositol labeling and phosphorylase activation were antagonized by PMA in cells from obese and lean animals; bigger residual effects were observed in cells from obese animals even at high PMA concentrations. Cyclic AMP accumulation induced by isoproterenol, glucagon, forskolin and cholera toxin was higher in cells from lean animals than in those from obese rats. PMA diminished glucagon- and cholera toxin-induced cyclic AMP accumulation; cells from lean animals were more sensitive to PMA. Two groups of isoforms of protein kinase C (PKC) were observed in hepatocytes from Zucker rats using DEAE-cellulose column chromatography: PKC 1 and PKC 2. The PKC 1 isozymes were separated into four peaks using hydroxylapatite: aa, 1a (PKC-beta), 1b (PKC-alpha) and 1c. Short treatment with PMA decreased the activity of PKC 1 (peaks 1b (PKC-alpha) and 1c) and to a lesser extent of PKC 2; cells from lean animals were more sensitive to PMA than those obtained from obese rats. Our results indicate that cells from genetically obese Zucker rats are in general less sensitive to this activator of protein kinase C than those from their lean littermates. The possibility that alterations in the phosphorylation/dephosphorylation cycles, that control metabolism and hormonal responsiveness, may contribute to this obese state is suggested.
研究了佛波酯（PMA）对瘦型和肥胖型 Zucker 大鼠肝细胞激素反应性的影响。苯肾上腺素刺激的磷脂酰肌醇标记和磷酸化酶激活在肥胖和瘦型动物的细胞中均被 PMA 拮抗；即使在高 PMA 浓度下，肥胖动物细胞中仍观察到更大的残余效应。异丙肾上腺素、胰高血糖素、福斯高林和霍乱毒素诱导的环磷酸腺苷（cAMP）积累在瘦型动物细胞中高于肥胖大鼠细胞。PMA 减少了胰高血糖素和霍乱毒素诱导的 cAMP 积累；瘦型动物细胞对 PMA 更敏感。使用二乙氨基乙基纤维素柱色谱法在 Zucker 大鼠肝细胞中观察到两组蛋白激酶 C（PKC）同工型：PKC 1 和 PKC 2。使用羟基磷灰石将 PKC 1 同工酶分离为四个峰：aa、1a（PKC-β）、1b（PKC-α）和 1c。PMA 短期处理降低了 PKC 1（峰 1b（PKC-α）和 1c）的活性，并在较小程度上降低了 PKC 2 的活性；瘦型动物细胞比肥胖大鼠细胞对 PMA 更敏感。我们的结果表明，与瘦型同窝仔鼠相比，遗传性肥胖 Zucker 大鼠的细胞对这种蛋白激酶 C 激活剂通常不太敏感。提示控制代谢和激素反应性的磷酸化/去磷酸化循环的改变可能导致这种肥胖状态。
