Hepatic extraction and renal production of 3,3'-diiodothyronine and 3',5'-diiodothyronine in man.
AUTOR(ES)
Faber, J
RESUMO
The sequential deiodination of thyroxine (T4) gives rise to several iodothyronine analogs including 3,3'-diiodothyronine (3,3'-T2) and 3',5'-diiodothyronine (3',5'-T2). In vitro animal studies suggest that the liver and the kidneys are the main sites of both formation and degradation of 3,3'-T2 and 3',5'-T2. To determine the metabolism of 3,3'-T2 and 3',5'-T2 in human liver and kidneys plasma samples were obtained from (a) a brachial artery and a hepatic vein in 20 normal subjects, and from (b) a femoral artery and a renal vein in 11 normal subjects. Further, the hepatic plasma flow (a) and the renal plasma flow (b) were determined. Both plasma 3,3'-T2 and 3',5'-T2 levels were reduced in the hepatic venous blood as compared to arterial values (1.09 +/- 0.40 vs. 1.75 +/- 0.74 ng/dl (P < 0.02)) (mean +/- 1 SD). This resulted in a hepatic extraction of both, 3,3'-T2 and 3',5'-T2, which averaged 8.2 and 5.2 microgram/d, respectively. Plasma 3,3'-T2 as well as 3'5'-T2 levels were higher in the renal vein as compared to arterial values, 1.49 +/- 0.42 vs. 1.39 +/- 0.45 ng/dl (P < 0.05) and 2.35 +/- 0.83 vs. 2.09 +/- 0.81 ng/dl (P < 0.05), respectively. This positive venoarterial difference implies a net production of 3,3'-T2 and 3',5'-T2 in the kidneys of 1.2 and 3.0 microgram/d, respectively. It is concluded that the liver is an important site of 3,3'-T2 and 3',5'-T2 extraction in normal man. In contrast, the renal production of 3,3'-T2 as well as 3'5'-T2 exceeds the degradation and urinary excretion.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=371529Documentos Relacionados
- 3,3′-Diiodothyronine Production, a Major Pathway of Peripheral Iodothyronine Metabolism in Man
- Thyroid Hormonelike Actions of 3,3′,5′-l-Triiodothyronine and 3,3′-Diiodothyronine
- Kinetic parameters and renal clearances of plasma adenosine 3′,5′-monophosphate and guanosine 3′,5′-monophosphate in man
- Hepatic and extrahepatic glucuronidation of bile acids in man. Characterization of bile acid uridine 5'-diphosphate-glucuronosyltransferase in hepatic, renal, and intestinal microsomes.
- Evidence that 1,25-dihydroxyvitamin D3 inhibits the hepatic production of 25-hydroxyvitamin D in man.