ABSTRACT
Aim To observe the changes of diaphragm contractility and cytoskeletal proteins titin,nebulin and sarcoplasmic reticulum Ca~(2+)-ATPase gene expressions in adriamycin-induced cytotoxicity in rats.Methods The animal models of diaphragm damage were duplicated by injecting adriamycin into abdominal cavity one time.Forty male sprague-dawley rats were randomly divided into four groups(n=10):Three groups received adriamycin in low,middle and high dosage(10,20 and 40 mg·kg~(-1))respectively.Meanwhile,the normal saline was given to rats in control groups.Three days later,these rats were killed,and the diaphragm was removed by thoracotomy.The diaphragm contractility was assessed in isolated diaphragm strips perfusion by these paramemters including peak twitch tension(Pt),maximum tetanic tension(Po),time to peak contraction(CT),half relaxaion time(1/2RT),maximal rates of contraction(+dt/dt_(max))and maximal rates of relaxation(-dt/dt_(max)).The expressions of titin,nebulin and sarcoplasmic reticulum Ca~(2+)-ATPase(SERCA)at mRNA level were detected by RT-PCR analysis.Results In contrast to those in control group,Po,Pt,±dt/dt_(max) in the adriamycin group were lower(P<0.01);CT,1/2RT in the adriamycin group increased significantly(P<0.01).The levels of titin,nebulin and SERCA gene expressions in middle-dose group were lower than those in control group(P<0.01).Conclusions The mRNA levels of titin,nebulin and SERCA of diaphragm are down-regulated in adriamycin-induced cytotoxicity in rats.It may be associated with the decline of diaphragm contractility.