I don't know that there is a good, reliable way to strip tissue sections -- only western blots. It is my experience that you could co-stain for something else, but not strip and remove an original antibody staining. Is there a reason why you're stripping and not just staining for Cx-43 with a difference secondary? I also assume these sections were cover slipped and treated with an anti-fade agent? I fear that, unfortunately, you might be out of luck if your goal is to remove all ki67 staining prior to Cx-43 staining.

I found some protocols online (see link below), but they don't seem to be very reliable. The buffers used are highly similar to those used in stripping western blots, where membranes are incubated in warm acidic buffers with lots of SDS and denaturing agents to disrupt protein-protein interactions. Like western blotting, it is virtually impossible to strip the antibodies without altering the antigen itself, and stripping is incomplete and highly variable. The procedure itself will be rough on thinly sectioned tissues, potentially disrupting the cytoarchitecture. It would also likely preclude the chance of doing any type of quantitative analysis.

Personally, I would be very weary of stripping tissues and would only give it a shot if it was the last choice (no more fresh tissue left, etc.)

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2690408/

Hello, do you mind sharing your protocol for the Ki67 staining? I'm using an anti-goat Ki67 from SantaCruz and am having no luck. I'm not getting any specific nuclear staining and have tried various lengths of HIER as well as using a DNase treatment.

Hello. Sorry for my late reply. I'm using the following protocol: Antigen retrieval of the sections was performed by microwave heating in sodium citrate buffer, 3 times for 5 minutes. The sections were then permeabilized in 0.2% Triton v/v for 10 minutes and blocked in PBS-1% BSA w/v for 1 hour. Sections were incubated with anti-Ki67 rabbit antibody overnight at 4°C. After washing in PBS, sections were incubated with secondary FITC Donkey anti-rabbit IgG antibody (Jackson ImmunoResearch) for 1h at room temperature. Following washes for 3x10 min in PBS, the sections were stained with Hoechst and mounted with PBS-50% v/v Glycerol.