Expert: Florence M Rollwagen - 5/2/2009

Question
Hi Florence,
I am a graduate student in maths trying to understand biological process for modelling.  My question is about lactate degradation. From litreture, I understand that when lactate is produced in a glycolytic cell, depending on the gradient, it will be exported by MCT4. Lactate then enters oxidative cell via MCT1 and it is converted back to pyruvate producing ATP. Here we see that lactate is degraded into pyruvate in an oxidative cell.  I was wondering if this (lactate conversion) also happens in a glycolytic (hypoxic) cell?
I am also trying to find the rate at which this occurs, but I was hopeless.  Are you aware of or you think there is any data regarding the rate at which lactate is converted to pyruvate?
Now, if lactate is NOT converted to pyruvate in a hypoxic cell, is it ok to assume that lactate naturally decays inside the cell as time evolves.

I appreciate your time to respond, Many thanks.
Maria


Answer
Hi Maria:  Thanks for your question.

Although this is WAAAY outside my expertise, I do have a few thoughts, based on my primitive understanding of metabolism.

ATP synthesis requires an energy source, usually oxygen.  I would think that not much ATP production would occur in a hypoxic cell.

Cells are permeable to lactate, which is why we can measure it in the bloodstream, so I think it would not decay inside the cell.

If I were going to try to measure the conversion rate, I would use a few cell culture lines and subject them to hypoxia in vitro.  Trying to estimate the conversion rate in an intact animal would be hopeless, given the many different kinds of cells present.

Just a few thoughts, hope this helps.

FM Rollwagen, PhD