Friday, December 19, 2008

Drats

Last week we wrapped up the first arm of our rat study. The study was time consuming, in that I had to drive into work 2-3 times per day to check on them and do testing. It was also interesting in that we learned to develop our protocol along the way. For example, one of the symptoms that we were looking for was renal failure, so we were monitoring urine output. At first, we were going to base this on cage weights, but that seemed too variable. Then we decided to line the cages with an absorbant pad that we could easily glance at for urine output. The rats responded in kind by chewing up the pad to make nesting material. Finally, we had to resort to wire cages with pads below to collect specimens. This, of course, required more paperwork.

This was the control arm of the study, so we were giving the rats a known chemical compound, and then treating them with placebo (saline). The next arm of the study would be administering the same weight-based dose of chemical to a new group of rats, only this time administering a likely antidote with the expectation that there would be less behavioral changes and less cellular damage.

Our dose of toxin was based on an "established" LD50 from other people's research (Being a child of the 80's I'm going to call this O.P.R.). LD50 is short for lethal-dose 50, and means that 50% of subjects receiving that dose should die. This is somewhat variable given that nothing in medicine is exact. From OPR, death or at least renal failure was expected to develop in 3-5 days. Our control arm was 10 days long.

Unfortunately, we ran into a huge problem: NONE of the rats died. There was some weakness noticed with behavior testing and at least one of the rats was doing some odd drunken head-bobbing, but that was about all that we noticed.

Being the suspicious women that we are, we had ordered extra rats in case some of them failed the baseline neuro testing, so we had a few extra rats to work with. On day 6, we gave those extra rats double the LD50 and....

NONE of them died, either!

So now there's a huge problem with our study in that if our chemical compound is not actually toxic at the dose we gave, we can't really proceed with the antidote arm. We have contacted the people behind OPR, and not really gotten anything other than, "hmm, that should have worked." Currently, our tissue samples are with the pathologist, so hopefully there will be some sort of changes at the cellular level, otherwise we have to either ditch the remainder of the study or do another study to first determine the proper LD50.

In trying to figure out what went wrong we've thought of:
1. Maybe our chemical isn't what the label says it is (and it didn't have an expiration date), so we have sent samples to an outside lab for analysis.
2. Maybe by administering saline we prolonged the renal failure and study wasn't long enough to reach our endpoints of renal failure/death.
3. Maybe our math was wrong, but it's been quadruple-checked.
4. OPR was wrong, and we need to do a separate LD50 study.

So there has been a lot of learning with this project. Either way, I have something to present for my required academic project, but I really wanted this to work. There have been a few accidental contaminations in consumer products with this compound, and it would have been cool to be part of the research behind developing a protocol for treating an ingestion. There are still blood tests pending as well, so for now, I am crossing my fingers and trying to be patient.

4 comments:

Chris said...

Interesting post, it reminded me of my Basic Toxicology class in school.

I also noticed that Oak Ridge National Laboratory has discontinued it's rodent projects, so I have another theory. Your rats came from Oak Ridge (which is chock full of all kinds of fun transuranic radioactive materials) and they have mutated into superrats that are immune to known toxins. Be nice to those rats....they are going to take over the world, ala Pinky and The Brain.

~~Silk said...

Hmmm. My bet goes on #1. Let us know what the lab says.

ru said...

Maybe they've been hiding the pills under their tongue :) Okay, you're not giving them pills; that's all I got. Curious to see how it turns out. Die, rats, die!

Kate said...

ru: and to think I was worried you might be offended by my animal testing! :)