You should assay the toxicity of your drug in your cell system by a dose dependent experiment, or look for it in pub-med.  I think you should , first to induce the membrane proteins, than add the drug for 6-8h before fixation, not more.

You may also try temperature block at 20-25C. That way you needn't worry about the chemical toxicity much, as longer incubation times leads to golgi fragmentation. Thats not good.

I would definitely try temperature arrest first and see whether that procedure does the job. 

If you want to block the anterograde Golgi to plasma membrane transport, you could try using commercially available drugs like brefeldin A, which inhibits the Arf--guanine nucleotide exchange factor (GEF).

There is also a newer ligand, called AMF-26, which affects the Arf-1 directly. 

Thank you for your answers guys. Could you explain the temperature block a little more please?

please try these reference:

Griffiths, G., Pfeiffer, S., Simons, K. and Matlin, K. (1985). Exit of newly synthesized membrane proteins from the trans cisterna of the Golgi complex to the plasma membrane. J. Cell Biol. 101, 949-964.

Kuliawat, R. and Arvan, P. (1992). Protein targeting via the “constitutive-like” secretory pathway in isolated pancreatic islets: passive sorting in the immature granule compartment. J. Cell Biol. 118, 521-529.

Simon, J. P., Ivanov, I. E., Adesnik, M. and Sabatini, D. D. (1996). The production of post-Golgi vesicles requires a protein kinase C-like molecule, but not its phosphorylating activity. J. Cell Biol. 135, 355-370.

There is a drug called monensin, that is a proton pump inhibitor.  It is ethanol soluble and I think it works optimally at 10 uM, but check details.  I believe I used it in these studies.  Cool thing is that the effect is immediately reversible by simple removal and wash of cells with media.  For example, you can block receptor transit to cell surface, deplete with ligand, block with monensin, remove monensin, and then watch recovery in real time by doing cell surface binding assays.  Good luck!

Relationship between epidermal growth factor receptor occupancy and mitogenic response. Quantitative analysis using a steady state model system

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