Separation of iodothyronines from iodinated metabolites in serum from reverse T3 tracer kinetic studies in man and dog: a comparison of two methods.
Iodothyronine separation from free iodide and iodoalbumin in serial serum samples obtained from 7 human and 5 dog studies following intravenous injection of radiolabeled reverse triiodothyronine (reverse T3) was compared using acidified ammonium acetate/tetrahydrofuran (THF) elution from C-18 SEP-PAK cartridges or ethyl acetate/butanol (EAB) extraction. Both methods excluded greater than 98% free iodide and greater than 99% iodoalbumin from the iodothyronine fraction. Recovery of labeled reverse T3 was higher for the THF/SEP-PAK (79.4 +/- 4.1%) than for the EAB method (43.2 +/- 6.1%, P less than 0.001), and intra-assay coefficients of variation were lower (2.1 +/- 0.6% and 4.4 +/- 2.0%, respectively, P less than 0.001); HPLC analysis of iodothyronine fractions revealed a single peak co-migrating with injected tracer. The THF/SEP-PAK technique allowed use of larger serum samples at later time points. Serum disappearance curves derived from these two methods were highly correlated in all cases (r = 0.998, P less than 0.001), as were fits of data to sums of exponentials and calculated serum kinetic parameters.
Kaptein
E M
EM
Department of Medicine, University of Southern California, Los Angeles.
Hoopes
M T
MT
Pattabhiraman
R
R
Akmal
M
M
Massry
S G
SG
D000085:Acetates; D000818:Animals; D000440:Butanols; D004285:Dogs; D005663:Furans; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D008722:Methods; D015203:Reproducibility of Results; D012997:Solvents; D013970:Thyronines / Q000097:blood / Q000302:isolation & purification*; D014285:Triiodothyronine, Reverse
D000085:Acetates; D000440:Butanols; D005663:Furans; D007457:Iodine Radioisotopes; D012997:Solvents; D013970:Thyronines; C018674:tetrahydrofuran; D014285:Triiodothyronine, Reverse; C007650:ethyl acetate; C018824:ammonium acetate