Effect of 6-hydroxydopamine and α-methyltyrosine on brown adipose tissue of infant rats

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Abstract
A single-dose administration of 6-hydroxydopamine (50 mg/kg body weight, sc) to infant rats resulted in an enlargement, higher fresh weight, markedly elevated lipid content, and higher total protein content of their interscapular and cervical brown adipose tissue. The protein kinase (EC 2.7.1.37) activation ratio in the tissue was decreased as was the phosphoenolpyruvate carboxykinase (EC 4.1.1.32) activity. Fatty acid synthetase, on the other hand, showed an increased activity. These changes commenced as soon as 24 h after the administration of the drug, were fully developed 2–4 days later, and persisted for at least 14 days. The results are in line with the assumption that 6-hydroxydopamine administration causes chemical sympathectomy of brown adipose tissue. This is further supported by the fact that treatment with α-methyltyrosine, which is known to competitively inhibit norepinephrine synthesis, results in similar changes in brown fat of infant rats. Hence it seems that 6-hydroxydopamine administration offers a simple and inexpensive experimental model for studies of the role of the norepinephrine-mediated sympathetic nervous system in brown adipose tissue function and development.