L-Arginine metabolism in cardiovascular and renal tissue from hyper- and hypothyroid rats.

This study assessed the effects of thyroid hormones on the enzymes involved in l-arginine metabolism and the metabolites generated by the different metabolic pathways. Compounds of l-arginine metabolism were measured in the kidney, heart, aorta, and liver of euthyroid, hyperthyroid, and hypothyroid rats after 6 weeks of treatment. Enzymes studied were NOS isoforms (neuronal [nNOS], inducible [iNOS], and endothelial [eNOS]), arginases I and II, ornithine decarboxylase (ODC), ornithine aminotransferase (OAT), and l-arginine decarboxylase (ADC). Metabolites studied were l-arginine, l-citrulline, spermidine, spermine, and l-proline. Kidney heart and aorta levels of eNOS and iNOS were augmented and reduced (P < 0.05, for each tissue and enzyme) in hyper- and hypothyroid rats, respectively. Arginase I abundance in aorta, heart, and kidney was increased (P < 0.05, for each tissue) in hyperthyroid rats and was decreased in kidney and aorta of hypothyroid rats (P < 0.05, for each tissue). Arginase II was augmented...