Calcineurin and heat-shock proteins modulation in clenbuterol-induced hypertrophied rat skeletal muscles.

To examine the changes in heat shock proteins (HSPs) and calcineurin (CaN), a calcium/calmodulin regulated protein phosphatase, in hypertrophied rat skeletal muscles, adult male Wistar rats were administered clenbuterol (CLB, 30 mg l(-1) in drinking water), a beta 2-agonist, for 4 weeks. Compared to controls, CLB-treated rats had significantly larger body (10%) and relative (to body weight) soleus (Sol, 16%), plantaris (Plt, 32%) and gastrocnemius (Gast, 27%) weights. Immunohistochemically classified fast fibers were hypertrophied in the Sol (64%), Plt (62%), and deep (d, 70%) and superficial (s, 44%) regions of the Gast, whereas slow fibers were hypertrophied only in the Plt (47%).