cfmendez

Hi CharonY, thank you very much for your reply. I'll try to answer your questions and comments. I agree although I believe that's certainly true for proteins exhibiting a high turnover rate. Is this the case of CAT and SOD? As judged from experiments where I measured ROS levels using DCHF and by ERK1/2 activation the answer is 5 minutes or less. I think the mechanism behind oxidative stress involves DA biotransformation to DA-quinone and aminochrome. But, again, is it reasonable to observe changes in activity? What would happen to CAT and SOD during the initial phase of oxidative stress? At the end of the day I feel that is the true question here.

Hi everybody, I'm new to this forum so I briefly introduce myself. I am a researcher at the Department of Biochemistry of the School of Medicine at Buenos Aires, working in the area of electrolyte transport in renal proximal tubule cells. My project deals mainly with the effect of dopamine (DA) that acts as a physiological regulator of Na,K-ATPase activity in the proximal tubule. Now, I have confirmed that DA increases the concentration of reactive oxygen species (ROS) even at minute concentrations, a result that moved me to explore both catalase (CAT) and superoxide dismutase (SOD) enzyme activities. I have measured CAT and SOD in cells exposed to DA and found a time-dependent decrease for CAT and increase for SOD. I would have no problems with those results, except that the time frame is minutes of DA exposure. Let´s get this clear I see significant increases and decreases in SOD and CAT activities respectively already after 15 min. I searched for articles in hope of similar results only to find descriptions of CAT and SOD regulation at transcriptional levels and after several hours or even days of stimulation. I may have miss the point, but the only reference I could find of use is one paper describing SOD regulation by phosphorylation in Listeria. I asked around and got a definite no for answer. Neither CAT nor SOD are subjected to activity regulation I've been told, and people see effects at mRNA level at much longer times than the ones I use. One last detail. The times employed in my experiments are not arbitrary of course. DA regulation of NKA activity is a very fast process. Already after 2 minutes you see an effect, therefore all my experiments are done using that time frame. The obvious question is: do my results make sense? I'll be most glad to read you comments and opinions. Thanks in advance Carlos