by Sharon Beder
Extrapolating Results to Animals and People
Once the in vitro work has been done Mason intends to collaborate with other groups to test some of these things in tanning hairless mice and also in human volunteers, in association with the photobiology testing unit and the Department of Dermatology. There is always a problem extrapolating from test tube results to animals and humans which is why it is necessary to go on to do some of the animal studies. The experience in other areas indicates it is not possible to totally recreate the organ to be investigated in a test tube.
The big advantage of the test tube work is that it allows you to dissect everything out, says Mason. You can do studies at the molecular and cellular level and say that X causes Y in the cell and why it does it. However, in a living body there may be 50 to 100 Xs and the effects that predominate depend on what other hormones are also around. Whereas a hormone or a cell produced substance may have a particular effect in a nice clean laboratory system if you start putting 2 or 3 other hormones in as well the effect may be entirely different. This is a difficulty that must always be kept in mind.
Apart from the difficulties in extrapolating the in vitro (test tube) results to the in vivo (life) situation there are also some difficulties going the other way. For instance, it is believed that pigmentation observed in vivo is often very marked in people with pituitary tumours and is likely to be due to the melanocyte stimulating hormones. But until Mason's team were able to demonstrate it recently, no other researchers were able to confirm it by reproducing the effect in vitro. Because of the difficulties of setting up an in vitro system that mimics skin it is not always possible to demonstrate what you think happens in vivo in the in vitro situation. So the problems work both ways.