Ultrastructural study on the effect of dexamethasone with and without clenbuterol on the diaphragmatic muscle of adult male albino

ABSTRACT

Animal and clinical studies have shown respiratory muscle dysfunction caused by treatment with glucocorticoids. Beta-agonists and glucocorticoids are frequently coprescribed for chronic asthma treatment. This work was done to investigate whether clenbuterol was able to ameliorate the structural changes induced hr long-term low-dose dexamethasone administration. Muscle samples were obtained from five groups of adult rats group I, represents the control rats; group II. represents Sham control animals, group III represents animals receiving clenbuterol orally; group IV represents animals receiving dexamethasone subcutaneously, whereas, group V represents animals receiving both, treatment [dexamethasone and clenbuterol]. At the end of 4th week, rats were anaesthetized, perfused with, 1.5% buffered gluteraldehyde and then sacrificed. The diaphragmatic muscle strips were immersed in 2.5% buffered gluteraldehyde for 24 hours, postfixed in 1% OsO[4] for 2 hours and then, processed to be examined with TEM. Dexamethasone induced myofibrillar disorganization and destruction. The distinct ban ding pattern of sarcomeres was lost. The mitochondria showed increased subsarcolemmal aggregation, transverse orientation, and destruction of their cristae. Sarcoplasmic reticulum showed irregularity, dilatation, and loss of their relationship to A-I junctions. Also, mononuclear cellular infiltration was observed. In combined treatments [DEX + CL], the changes induced by DEX alone were generally minimized. Dexamethasone could induce severe structural changes in the diaphragmatic muscle of rat, timid these changes could be generally minimized on concomitant administration of clenbuterol