DALLAS - October 29, 1998 - Myoglobin, the protein long thought to be the sole carrier of oxygen to heart and certain skeletal muscle, is not necessary for survival, UT Southwestern Medical Center at Dallas scientists reported in today's issue of the journal Nature.
Because of this discovery, investigators will be able to delve further into causes, prevention and cures for heart failure. The researchers made their breakthrough by developing a strain of mice lacking the gene to produce myoglobin, which transports oxygen from capillaries to mitochondria in heart and endurance muscle cells. Mitochondria are the structures within cells that transform oxygen and other molecules into energy for all cellular functions.
"Myoglobin is found in the heart and the slow-twitch, or endurance, skeletal muscles in a number of species. So because of its prevalence and the energy required for contraction of the heart, we predicted that mice could not live without this protein," said Dr. Dan Garry, assistant professor of internal medicine and first author of the report. "We were surprised that not only did they survive without it, they were born, developed, reproduced, nurtured and exercised normally."
The mice were exercised on treadmills along with littermates that had myoglobin. All the animals were exposed to conditions simulating different altitudes at which the body would normally experience some lack of oxygen. Neither group showed any differences in their behavior or their ability to handle the different conditions.
The only alteration researchers found in the rodents lacking myoglobin was that the heart and endurance muscles were nonpigmented or almost white rather than a rich pink because most of the red color actually comes from the myoglobin.
"Our research suggests that the system transferring the oxygen necessary
to fuel the contraction of heart and slow-twitch muscles is much more
complicated than the long-he
Contact: Susan Steeves
UT Southwestern Medical Center