Epinephrine synthesis in rat skeletal muscles

ABSTRACT

Local epinephrine [E] synthesis in skeletal muscle was investigated in sham-operated and bilaterally adrenalectomized rats. E forming activity [EFA] of phenylethanolamine-N-methyltransferase enzyme [PNMT] in skeletal muscle was not affected by bilateral adrenalectomy alone but was induced significantly following chronic propranolol administration [1 mg/kg i.p. twice daily for 8 days]. Bilateral adrenalectomy did not decrease muscle E content but decreased resting and stress plasma E levels. Plasma E was still detectable 10 days after bilateral adrenalectomy. The results suggest that local synthesis of E in rat skeletal muscle is possible. Chronic propranolol administration lowered muscle E content significantly and decreased stress plasma E value compared to the corresponding resting value, in bilaterally adrenalectomized but not in sham-operated rats. Propranolol may, therefore, interfere with E mediated mechanisms to severe stress in absence of adrenal glands resulting in lowering skeletal muscle and plasma E levels in stressful conditions