5'-nucleotidase activity is altered by hypo- and hyperthyroidism in platelets from adult rats.
Thyroid disorders are associated to a number of vascular diseases that involve processes such as platelet aggregation and vascular tone control. Since, these processes can be also affected by ATP, ADP and adenosine levels, we investigate the hydrolysis of these nucleotides in platelets from hyperthyroid, hypothyroid, and hypothyroid with hormonal replacement rats. Hyperthyroidism was induced by daily injections of L-thyroxine (T4) 25 microg/100 g body weight for 14 days. Hypothyroidism was induced by thyroidectomy and methimazole (0.05%) for 14 days. In the hormonal replacement group, hypothyroid rats were injected with T4 (5 microg/100 g body weight, i.p.) for 5 days. The AMP hydrolysis by platelets was increased 49% in hyperthyroid rats and decreased 50% in response to hypothyroidism, while the ATP and ADP hydrolysis was not altered in both groups. Besides, the T4 replacement significantly reversed the inhibition of the AMP hydrolysis observed in hypothyroid rats. Our findings indicate that the thyroid disorders affect the 5'-nucleotidase activity and consequently can alter the adenosine levels in a reversible manner in platelet fraction. Since, adenosine is able to inhibit platelet aggregation and acts as a potent vasodilator, these results can contribute to a better comprehension of the vascular events described in thyroid disorders.
Bruno
Alessandra Nejar
AN
Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Avenida Ramiro Barcellos, 2600-ANEXO 90035-003 Porto Alegre, RS, Brazil.
Pochmann
Daniela
D
Ricachenevsky
Felipe Klein
FK
Bonan
Carla Denise
CD
Barreto-Chaves
Maria Luiza M
ML
Freitas Sarkis
João José
JJ
D015720:5'-Nucleotidase / Q000187:drug effects / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001792:Blood Platelets / Q000201:enzymology* / Q000473:pathology; D004195:Disease Models, Animal; D006980:Hyperthyroidism / Q000201:enzymology*; D007037:Hypothyroidism / Q000201:enzymology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013974:Thyroxine / Q000008:administration & dosage / Q000494:pharmacology
D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D015720:5'-Nucleotidase; D013974:Thyroxine