I have planned an experiment where I intend to increase circulating levels of adenosine / s-adenosyl methionine in the mouse blood stream and check its effect on plasmodium berghei? Should I put these metabolites in water and feed orally or should I go for injection (IP or retro-orbital). Which is the best way?
Hi Lakshmeesha
You cannot give adenosine orally as it is broken down very rapidly and you would not achieve a therapeutic dose. The red cells also rapidly metabolise the adenosine so I am not sure you will see any therapeutic effect using the technique even if you do administer by IV (via the tail vein) which would be the route that I would use. I am not sure of the fate of s-adenosyl methionine but would suggest looking up the pharmacokinetics of this compound before proceeding with the study. What doses are you wanting to administer and for how long?
Good luck
Duncan
Thank you very much for your response. I need to follow the effect for atleast a week. I came across papers where people have used 400mg/kg body weight. But here they study the effect on mouse itself. In my case I want to see the effect on the parasite. Also adenosine solubility is very low (1mg/ml in water).... SAM is 100mg/ml....
Hi Lakshmeesha
I am sure those doses of adenosine would cause serious cardiac effects. If it was dosed orally I do not think much of the adenosine would have made it into the plasma anyway.
The uptake of adenosine into red blood cells is very rapid but it is then converted into metabolites such as inosine, xanthine, hypoxanthine and uric acid. Hypoxanthine is added to malaria culture media in the laboratory to aid parasite growth so I do not know what the objective of your study is but I do not think it would be considered an anti-malarial.
Duncan
Dear Professor Cromarty,
I have generated a knockout strain of P berghei (AMP deaminase has been knocked out). In yeast, AMP deaminase knockout shows growth defect in media containing SAM (SAM gets converted to adenosine in yeast cell and then to AMP. Accumulation of AMP is toxic for yeast as it perturbs adenylate energy charge) or adenine (Adenine also gets converted to AMP .Yeast can't take up adenosine ). Similar experiment is being tried in P berghei. As you said we add hypoxanthine to P falciparum culture. And hypoxanthine is known to rescue the growth defect seen in AMP deaminase knockout yeast. My objective is to see if there is any growth change upon knocking out AMP deaminase in the presence of adenosine or SAM which may get converted to AMP eventually. My hypothesis is; since a hypoxinthine salvage is already going on in Plasmodium, knocking out AMP deaminase and increasing AMP levels in parasite by using adenine/adenosine/SAM should not lead to any growth defect as seen in yeast. I need to test this hypothesis.
Thank you very much for your time and response
-lakshmeesha