'Suspended Animation' Induced In Mice With Sewer Gas: Effects Are Reversible

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'Suspended Animation' Induced In Mice With Sewer Gas: Effects Are Reversible

http://www.sciencedaily.com/releases/2008/03/080325083254.htm

ScienceDaily (Mar. 25, 2008) — Low doses of the toxic gas responsible for the

unpleasant odor of rotten eggs can safely and reversibly depress both metabolism

and aspects of cardiovascular function in mice, producing a

suspended-animation-like state. In the April 2008 issue of the journal

Anesthesiology, Massachusetts General Hospital (MGH) reseachers report that

effects seen in earlier studies of hydrogen sulfide do not depend on a reduction

in body temperature and include a substantial decrease in heart rate without a

drop in blood pressure.

" Hydrogen sulfide is the stinky gas that can kill workers who encounter it in

sewers; but when adminstered to mice in small, controlled doses, within minutes

it produces what appears to be totally reversible metabolic suppression, " says

Warren Zapol, MD, chief of Anesthesia and Critical Care at MGH and senior author

of the Anesthesiology study. " This is as close to instant suspended animation as

you can get, and the preservation of cardiac contraction, blood pressure and

organ perfusion is remarkable. "

Previous investigations into the effects of low-dose hydrogen sulfide showed

that the gas could lower body temperature and metabolic rate and also improved

survival of mice whose oxygen supply had been restricted. But since hypothermia

itself cuts metabolic needs, it was unclear whether the reduced body temperature

was responsible for the other observed effects. The current study was designed

to investigate both that question and the effects of hydrogen sulfide inhalation

on the cardiovascular system.

The researchers measured factors such as heart rate, blood pressure, body

temperature, respiration and physical activity in normal mice exposed to

low-dose (80 ppm) hydrogen sulfide for several hours. They analyzed cardiac

function with electrocardiograms and echocardiography and measured blood gas

levels. While some mice were studied at room temperature, others were kept in a

warm environment -- about 98º F -- to prevent their body temperatures from

dropping.

In all the mice, metabolic measurements such as consumption of oxygen and

production of carbon dioxide dropped in as little as 10 minutes after they began

inhaling hydrogen sulfide, remained low as long as the gas was administered, and

returned to normal within 30 minutes of the resumption of a normal air supply.

The animals' heart rate dropped nearly 50 percent during hydrogen sulfide

adminstration, but there was no significant change in blood pressure or the

strength of the heart beat. While respiration rate also decreased, there were no

changes in blood oxygen levels, suggesting that vital organs were not at risk of

oxygen starvation.

The mice kept at room temperature had the same drop in body temperature seen in

earlier studies, but those in the warm environment maintained normal body

temperatures. The same metabolic and cardiovascular changes were seen in both

groups, indicating that they did not depend on the reduced body temperature, and

analyzing the timing of those changes showed that metabolic reduction actually

began before body temperature dropped.

" Producing a reversible hypometabolic state could allow organ function to be

preserved when oxygen supply is limited, such as after a traumatic injury, " says

Gian Paolo Volpato, MD, MGH Anesthesiology research fellow and lead author of

the study. " We don't know yet if these results will be transferable to humans,

so our next step will be to study the use of hydrogen sulfide in larger

mammals. "

Zapol adds, " It could be that inhaled hydrogen sulfide will only be useful in

small animals and we'll need to use intravenous drugs that can deliver hydrogen

sulfide to vital organs to prevent lung toxicity in larger animals. " Zapol is

the Reginald Jenney Professor of Anaesthesia at Harvard Medical School.

The study was supported by grants from the National Institutes of Health and

Linde Gas Therapeutics. Additional co-authors of the Anesthesiology report are

Searles, Binglan Yu, PhD, Fumito Ichinose, MD, and Bloch, MD, MGH

Anesthesia; and Marielle Scherrer-Crosbie, MD, MGH Cardiology.

Adapted from materials provided by Massachusetts General Hospital, via

EurekAlert!, a service of AAAS.

Need to cite this story in your essay, paper, or report? Use one of the

following formats:

APA

MLA Massachusetts General Hospital (2008, March 25). 'Suspended Animation'

Induced In Mice With Sewer Gas: Effects Are Reversible. ScienceDaily. Retrieved

March 25, 2008, from

http://www.sciencedaily.com­ /releases/2008/03/080325083254.htm

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