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Apolipoprotein A-I Synthesis and Secretion Are Increased in Hep G2 Cells Depleted of Copper by Cupruretic Tetramine^1,2,3,

Department of Nutritional Sciences, University of Arizona, Tucson, AZ 85721

Two amine chelators, namely N,N'-bis(2-aminoethyl)-1,3-propanediamine-4 HCl (2,3,2-tetramine) and diamsar, were used at various levels to deplete copper (Cu) from cultured Hep G2 cells. For cells cultured at 0.63 µmol of Cu/L, maximal depletions were attained after 24 h of incubation with 10 µmol of either chelator/L, which resulted in an average significant depletion of 45% of cellular Cu. In addition, when cells were cultured continuously for four passages at 0.63 µmol Cu/L with 20 µmol of 2,3,2-tetramine/L, cellular Cu was significantly depleted more than 40% compared with controls. Furthermore, after two passages of 2,3,2-tetramine treatment, cells were pulsed for 10 min with [³H]leucine and chased up to 2 h. At the end of the pulse, the amount of [³H]leucine incorporated into apolipoprotein A-I was twofold greater (P < 0.05) in treated than in control cells. No difference was detected for the synthesis of apolipoprotein B and total protein. During the chase, the cellular depletion curves for apolipoprotein A-I, apolipoprotein B and total protein were not altered by 2,3,2-tetramine treatment. From 30 to 120 min of the chase, the amount of nascent apolipoprotein A-I degraded was small and not altered, but that secreted into the medium was 56% higher (P < 0.05) in the Cu-depleted than in the control cells.

KEY WORDS: • Hep G2 cells • cupruretic tetramine • apolipoprotein A-I synthesis • apolipoprotein A-I secretion

¹ This study was presented in the 1991 FASEB meeting (FASEB J. 5: A583) and the 1994 Experimental Biology Meeting (FASEB J. 8: A711).

² Supported by USDA Human Nutrition Competitive Grants Program (89-37200-4423) and funds from the University of Arizona Agricultural Experiment Station.

³ The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

⁴ Current address: Hipple Cancer Research Center, 4100 S. Kettering Boulevard, Dayton, OH 45439-2092.

⁵ To whom correspondence and reprint requests should be addressed.

Manuscript received 8 March 1994. Revision accepted 18 July 1994.