The Contractility of the Diaphragm under Hypoxic Conditions in Aged Rats

known to impair force generation and increases fatigability of respiratory and
peripheral skeletal muscles. The precise mechanisms involved in hypoxia-induced
impairment in contractile performance are incompletely understood, but oxidative
and nitrosative stress could be at play. Little is known about the effects of hypoxia on
the contractility of aged muscles. Aim: To investigate the effect of aging on the
contractility of unfatigued diaphragm under hypoxic conditions. And to ask whether
there is an age-specific difference in oxidative damage that could partially account for
the differential response of the contractility of the diaphragm to hypoxia with age.
Materials and Methods: This experimental work was conducted on 2 groups of
albino rats. Group I was the young adult rats (aged 8mo n=10). Group II was the old
one (aged 24mo,n=10). Rat diaphragm muscle strips from each group were studied in
vitro while aerated with 95% O2-5% CO2 (hyperoxia ,n=10) or 95% N2-5% CO2
(hypoxia,n=10). Results: The contractility was significantly decreased in old rats
when compared with young rats specially under hypoxic conditions. On the other
hand the markers of oxidative stress; MDA and nitrotyrosine were significantly
higher in old rats than adults. Conclusion: There is an age-specific difference in
oxidative damage that could partially account for the differential response of the
contractility of the unfatigued diaphragm to hypoxia with age.