P.R. Contact:
Claire Wagner
Office: (513) 529-7592
Home: (513) 521-0124
Research contact:
Jon Costanzo, Ph.D.
(513) 529-3173 or 529-3167
MORE CLUES TO LIFE AFTER ICE: HOW FROZEN FROGS THAW
OXFORD, Ohio ó A team of Miami University researchers has discovered another part of the process that allows certain reptiles and amphibians to freeze solid and then thaw back to healthy life.
Glucose, key to preserving wood frogs when they freeze during winter, is not flushed out of a frog's body when it thaws, but is reabsorbed into the bloodstream through the frog's urinary bladder, according to research by Drs. Jon Costanzo, Phyllis Callahan and Richard Lee, professors of zoology, and Michael Wright, research associate, all at Miami.
This new insight into the permeability of the bladder wall is explained in an article published in the Sept. 25 issue of the journal Nature.
Costanzo and Lee have long studied the freeze tolerance of several unusual species of amphibians and reptiles, creatures that freeze solid over winter and thaw back to life in the spring. The pair have identified four of the eleven species known to be freeze tolerant.
They've learned that glucose produced in the liver is transported in the blood to the cells of vital organs during freezing. The glucose enables cells to tolerate freezing. But, says Costanzo, during thawing when the glucose pours back into the bloodstream, it then spills into its urine (a diabetic condition).
Since the frogs thawed to pre-freeze health, the researchers figured they somehow retained the needed glucose.
The researchers found glucose passes from the wood frog's urine through the urinary bladder wall and back into the bloodstream and slowly returns to storage in the liver.
They repeated the study on non-freeze tolerant species to see if the process was related to glucose's role as a cryoprotectant. They had similar findings.
"These guys eat bugs, and have little sugar in their diets," says Costanzo. "Maybe it's a general carbohydrate conservation system." -30-
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