To test the role of PPAR in edema, Yang created mice that
specifically lacked PPAR-gamma in the collecting duct. He then
administered TZD to these mice, as well as to a control group
that didn't lack PPAR-gamma. The mice not lacking PPAR-gamma
showed about a 10 percent average increase in body weight
because of fluid retention. The blood plasma volume of these
mice increased by one-third, Yang said. But the mice bred
without PPAR-gamma experienced no increase in body weight in
response to the drug, according to Yang. "This tells us that the
body weight gain is regulated by PPAR-gamma in the collecting
duct," he said. "We also found this drug decreased the sodium
excretion in urine, so this could explain the fluid retention."
The mice without PPAR in the collecting ducts incurred no
changes in sodium reabsorption, while those with PPAR excreted
less sodium through urination. Yang said that the distal
nephron, which is usually subject to hormone regulation in the
kidney, serves as a key pathway for keeping an a