RESUMO
The effect of 4-nonylphenol (NP) on cell proliferation and adipocyte formation was examined in cultures of fully differentiated 3T3-L1 cells. Following the hormonal induction of differentiation into adipocytes, 3T3-L1 cells were treated for 8 days with or without NP. NP at 5 and 10 microg/ml increased the DNA content by 32% and 68%, respectively, compared with that of the untreated cultures, in which NP was absent during the treatment period. There were many more bromodeoxyuridine (BrdU)-positive cells in the NP-treated cultures, in which NP was present at a concentration of 10 microg/ml during the treatment period, compared to the untreated cultures. These results indicate that NP had the ability to stimulate the proliferation of fully differentiated 3T3-L1 cells. NP at 5 and 10 microg/ml decreased the triacylglycerol (TG) content by 26% and 58%, respectively, and decreased the lipoprotein lipase (LPL) activity by 51% and 71%, respectively. The lipid droplets in individual cells of the NP-treated cultures were smaller than those of the untreated cultures. The mRNA levels of LPL and adipocyte-specific fatty acid binding protein (aP2) were considerably lower in the NP-treated cultures than in the untreated cultures. Thus, NP also had the ability to inhibit adipocyte formation in cultures of fully differentiated 3T3-L1 cells. A study using an antiestrogen ICI 182,780 showed that the NP-stimulated cell proliferation was mediated partly by the estrogen receptor, while the NP-induced inhibition of adipocyte formation was mediated by a mechanism other than the estrogen receptor.
Assuntos
Células 3T3-L1/efeitos dos fármacos , Adipócitos/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Estradiol/análogos & derivados , Proteínas do Tecido Nervoso , Fenóis/toxicidade , Células 3T3-L1/metabolismo , Células 3T3-L1/patologia , Adipócitos/metabolismo , Adipócitos/patologia , Animais , Northern Blotting , Bromodesoxiuridina/metabolismo , Proteínas de Transporte/biossíntese , Proteínas de Transporte/genética , Contagem de Células , Divisão Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Estradiol/farmacologia , Moduladores de Receptor Estrogênico/farmacologia , Proteína 7 de Ligação a Ácidos Graxos , Proteínas de Ligação a Ácido Graxo , Fulvestranto , Lipase Lipoproteica/biossíntese , Lipase Lipoproteica/genética , Camundongos , RNA Mensageiro/metabolismo , Triglicerídeos/metabolismoRESUMO
The confluent cultures of 3T3-L1 fibroblasts were treated with or without bisphenol A (BPA) for 2 days and subsequently treated with insulin (INS) alone for 9 days. When BPA was absent during the first 2-day treatment period, the cultures contained 1.6 microg/microg DNA of triacylglycerol (TG), 202 mU/mg DNA of lipoprotein lipase (LPL) activity, and 462 nmol/min/mg DNA of glycerol-3-phosphate dehydrogenase (GPDH) activity. The presence of BPA during the same period caused a 150% increase in the TG content, a 60% increase in the LPL activity, and a 500% increase in the GPDH activity. Thus, BPA by itself can trigger 3T3-L1 fibroblasts to differentiate into adipocytes. Next, the confluent cultures were treated with BPA for 2 days and subsequently treated with a combination of INS and BPA for 9 days. The simultaneous presence of BPA with INS caused a 370% increase in the TG content, a 200% increase in the LPL activity, and a 225% increase in the GPDH activity compared with the cultures treated with INS alone. The amount of [(3)H]thymidine incorporated into DNA was lower in the cultures treated with INS in the presence of BPA than in those treated with INS alone, indicating that BPA has an anti-proliferative activity on 3T3-L1 cells. Taken together, our results indicate that BPA in combination with INS can accelerate the adipocyte conversion.
