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oic....Thank you for you all kindly explanation. Hopefully that i can do my assay well. Thanks!

yes....i did checked the pH values today. It's about pH9.0, and when i add in the HCl, the cloudy solution turn to clear already and the pH is about pH 7.48. thanks to remind me the pH values! () Thanks for reply, i solve the problem right now, as the sodium HEPES is a salt which will increase the pH values. It's go down when i add in HCl (and the cloudy solution turn to clear now..hehe...). However, I did add sodium bicarbonate, i would like to ask that will it affect the pH values also? Thanks!

Dear all, i had made few times the krebs-HEPES solution. And i found that the solution tend to be cloudy with precipitate. expecially when i add in CaCl2.2 H20, after the sodium HEPES. I tried turn over, which means that i add in CaCl2.2H20 ,then i add in sodium HEPES. But it's still turn to cloudy solution. I would like to ask that is it very important that the order to put in the chemicals? and if i continue to use the cloudy solution, will it affect my assay? for you information, the solution is clear before i add in the calcium cloride ot the sodium HEPES, and i also add very slowly for these two chemicals....thanks!

I am doing nitric oxide measurement using aorta tissue.I had go through some articles that stated that the tissues were frozen with liquid nitrogen and stored at -80 degree Celsius, then homogenates and continue to assay. Anyone can tell me that if i use the fresh tissues, incubate with drugs, then can i directly homogenates it and continue to the assay instead of store it at -80 degree Celsius before the assay? Thank you very much.

Thanks for your kindly reply. If any mistake in methodology, then all rings (4 rings in one set) should have the same result, but it's only 1-2 rings gave me the result as i mentioned previous.And sometimes, i got the vice versus result also....>0.5g of PE and <0.5g of high K. However, i would like to ask that is it the interval timing ( for adding the drugs like PE and high K) very important? Thank you.

i am doing research on hypertension, and mainly test on the function of aortic rings of hypertensive rats. Sometimes, i can not get a full contraction (>0.5g tension) induced by phenylephrine(PE,10-7M) but i can get the >0.5g tension contraction induced by high k(KCl,80mM) in the same ring. i have not incubate any drugs yet. Please tell me what's wrong with the rings? Thanks.