Modulation of liver mitochondrial NOS is implicated in thyroid-dependent regulation of O(2) uptake.
Changes in O(2) uptake at different thyroid status have been explained on the basis of the modulation of mitochondrial enzymes and membrane biophysical properties. Regarding the nitric oxide (NO) effects, we tested whether liver mitochondrial nitric oxide synthase (mtNOS) participates in the modulation of O(2) uptake in thyroid disorders. Wistar rats were inoculated with 400 microCi (131)I (hypothyroid group), 20 microg thyroxine (T(4))/100 g body wt administered daily for 2 wk (hyperthyroid group) or vehicle (control). Basal metabolic rate, mitochondrial function, and mtNOS activity were analyzed. Systemic and liver mitochondrial O(2) uptake and cytochrome oxidase activity were lower in hypothyroid rats with respect to controls; mitochondrial parameters were further decreased by L-arginine (-42 and -34%, P < 0.05), consistent with 5- to 10-fold increases in matrix NO concentration. Accordingly, mtNOS expression (75%) and activity (260%) were selectively increased in hypothyroidism and reverted by hormone replacement without changes in other nitric oxide isoforms. Moreover, mtNOS activity correlated with serum 3,5,3'-triiodothyronine (T(3)) and O(2) uptake. Increased mtNOS activity was also observed in skeletal muscle mitochondria from hypothyroid rats. Therefore, we suggest that modulation of mtNOS is a substantial part of thyroid effects on mitochondrial O(2) uptake.
Carreras
M C
MC
Laboratory of Oxygen Metabolism, University Hospital, University of Buenos Aires, 1120 Buenos Aires, Argentina. jpoderos@fmed.uba.ar
Peralta
J G
JG
Converso
D P
DP
Finocchietto
P V
PV
Rebagliati
I
I
Zaninovich
A A
AA
Poderoso
J J
JJ
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D003576:Electron Transport Complex IV / Q000378:metabolism; D006980:Hyperthyroidism / Q000378:metabolism; D007037:Hypothyroidism / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008928:Mitochondria / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013974:Thyroxine / Q000494:pharmacology*
D001120:Arginine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat; D003576:Electron Transport Complex IV; D013974:Thyroxine