SOLEUS MUSCLE ALTERATIONS IN SPONTANEOUSLY HYPERTENSIVE RATS ARE NOT DEPENDENT ON ACTIVATION OF BETA-2-ADRENERGIC RECEPTORS

The effects of selective beta2-adrenergic blockade with ICI 118,551 on the histochemical, biochemical, and contractile properties of slow-tw itch soleus muscle from spontaneously hypertensive (SHR) and normotens ive (WKY) rats were examined from birth to 8-10 weeks of age. Chronic treatment of normotensive rats with ICI 118,551 caused an impairment i n the differentiation of slow type fibers during development but faile d to alter the fiber type distribution of hypertensive rats. Beta-adre noreceptor blockade was ineffective in reducing the enhanced glycolyti c and oxidative capacities of soleus in hypertensive rats. The suggest ion can be made that beta2-adrenoreceptor activation is not responsibl e, at least directly, for the histochemical and biochemical alteration s of slow muscle from hypertensive rats.