Sains Ma1aysiana 25(4) 1996: 123-130                                                                      Sains Hayat/

Life Sciences

Control of Adipose Tissue Lipoprotein Lipase

Expression by Isoproterenol

Halimah Abdullah Sani

Jabatan Biokimia

Fakulti Sains Hayat

Universiti Kebangsaan Malaysia

43600 UKM Bangi Selangor D.E. Malaysia

ABSTRACT

Isoproterenol decreased adipose tissue lipoprotein lipase (LPL) activity during in vitro incubation and the decrease was dose-dependent. The activity was reduced to 54.5% of the control (P<0.001) by 10 µM isoproterenol after 2h incubation. Isoproterenol did not alter general protein synthesis, LPL synthesis or relative LPL synthesis. It has no significant effect on general protein degradation but significantly increased LPL degradation. The percentage of LPL degradation was increase from 39.8% in the absence to 54.2% in the presence of 10 µM isoproterenol. The level of LPL mRNA as well as the ratio of LPL mRNA/α-tubulin mRNA were significantly decreased by 23% (P<0.05) during 2h incubation at 32°C. These results show that the control of adipose tissue LPL expression by isoproterenol occurred at the level of transcription and posttranslation.

ABSTRAK

Isoproterenol menurunkan aktiviti lipoprotein lipase (LPL) tisu adipose semasa pengeraman in vitro dan penurunan aktiviti ini bergantung kepada dos. Aktiviti LPL diturunkan kepada 54.5% daripada nilai kawalan (P<0.001) oleh 10 µM isoproterenol selepas 2 jam eraman. Isoproterenol tidak mengubah sintesis protein am, sintesis LPL ataupun sintesis LPL relatif. Isoproterenol juga tidak memberi kesan yang bererti ke atas degradasi protein am tetapi meningkatkan degradasi LPL dengan bererti. Peratus degradasi LPL meningkat daripada 39.8% ketika eraman tanpa isoproterenol kepada 54.2% semasa eraman dengan 10 µM isoproterenol. Aras mRNA LPL dan juga nisbah mRNA LPL/RNA α-tubulin menurun dengan bererti sebanyak 23% (P<0.05) semasa 2 jam eraman pada 32°C. Basil kajian ini menunjukkan bahawa kawalan pengekspresan LPL tisu adiposa oleh isoproterenol berlaku pada peringkat transkripsi dan postranslasi.

RUJUKAN/REFERENCES

AI-Jafari, A.A. and Cryer, A. 1986. Biochem J. 238: 239-246

Amersham. 1985. Membrane transfer and Detection Methods. Amersham International plc, U.K.

Ashby, P., Bennet, D.P, Spencer, I.M. and Robinson, D.S. 1978. Biochem. J. 176: 865-872.

Ashby, P. and Robinson, D.S. 1980. Biochem. J. 188: 185-192.

Ball, K.L., Speake, B.K. and Robinson, D.S. 1986. Biochem. Biophys. Acta 877: 399­-405.

Chomczynski, P. and Sacchi, N. 1987. Anal. Biochem. 162: 156-159.

Jones, S.M.A., Younan, S.I.M., Graham, A. and Rogers, M.P. 1986. Biochim. Biophys. Acta 878: 250-257.

Ong, J.M. Kirchgessner, T., Schotz, M.C. and Kern, P.A. 1988. J. Bioi. Chem. 263: 12933-12938.

Ong, J.M., Saffari, B., Simsolo, R.B. and Kern, P.A. 1992. Mol. Endocrinol. 6: 61-69.

Raynolds, M.V., Awald, P.D., Gordon, D.F., Gutierrez-Hartman, A., Rule, D.C., Wood, W.M. and Eckel, R.H. 1990. Mol. Endocrinol. 4: 1416-1422.