Summary: A radioimmunoassay for the measurement of 3.3',5'-triiodo-/,-thyronine (reverse T 3> rT 3 ) has been developed. The known limitations of this technique have been overcome by the use of the biologically relevant 1,-compound for the production of highly specific antisera and for preparing the standard curve. The high sensitivity of the assay (lower limit of detection 20 ng/1 serum) was obtained by using 125 I-labelled rT 3 of maximum specific radioactivity. Mean serum rT 3 concentrations for various thyroid states were as follows: Normal subjects: 0.182 jug/1 (0,280 nmol/1), hypothyroidism: 0.038 g/l (0.058 nmol/1), hyperthyroidism: 0.522 g/l (0.802 nmol/1), pregnants: 0.200 jug/1 (0.307 nmol/1), newborn (cord serum): 2.11 g/l (3.24 nmol/1). The method described should provide additional information with regard to the clarification of thyroxine metabolism. Radioimmunoassay für S.S'tS'-Trijod-L-thyronin (reverses T$) im menschlichen Serum und seine Anwendung bei verschiedenen Funktionszuständen der SchilddrüseZusammenfassung: Es wird die Entwicklung eines radioimmunchemischen Verfahrens zur Bestimmung von 3,3',5'-Trijod-L-thyronin (reverses T 3 , rT 3 ) im menschlichen Serum beschrieben. Durch die Verwendung der biologisch relevanten L-Verbindung zur Gewinnung hochspezifischer Antiseren sowie zum Ansatz der Standardkurven wurden Nachteile der einzigen bisher beschriebenen Methode überwunden. Die hohe Empfindlichkeit der Methode (untere Nachweisgrenze 20 ng/1 Serum) wurde durch Benutzung von 12S Jod-markiertem rT 3 mit maximaler spezifischer Radioaktivität erreicht. Für verschiedene Funktionszustände der Schilddrüse wurden die folgenden mittleren rT 3 -Serumkonzentrationen gemessen: Normalpersonen: 0.182 g/l (0.280 nmol/1), Hypothyreose: 0,038 g/l (0,058 nmol/1), Hyperthyreose: 0.522 g/l (0,802 nmol/1), Schwangere: 0,200 g/l (0,307 nmol/1), Neugeborene (Nabelschnurserum): 2,11 g/l (3,24 nmol/1). Die beschriebene Methode dürfte es ermöglichen, weitere Informationen zur Klärung des Thyroxinmetabolismus zu erhalten.
A radioimmunoassay for the measurement of 3,5-diiodothyronine (3,5-T2) using a 3H-labelled derivative of 3,5-T2 as tracer has been developed. The cross-reactivity of the antiserum was relatively high for T3 (3.1%) and low for T4 (less than 0.0015%). 3,5-T2 serum concentrations measured after fractional enrichment of 3,5-T2 were near or below the detection limit of 0.1 nmol/l in ten normal subjects and 0.38 nmol/l in five hyperthyroid patients. 3,5-T2 was also detected in thyroid tissue. The serum half-time of 3,5-T2 estimated after injection of 2 mg 3,5-T2 in three normal volunteers was 4.5 h.
Radiation from 99mTc was measured at typical locations in those areas of a nuclear medicine department where approximately 50 Ci 99mTc is used per year. In addition, measurements of shielded and unshielded syringes containing 99mTc-labelled radiopharmaceuticals were carried out. From these data radiation exposure of hands and of the whole body of personnel was calculated, taking into consideration the mean working times in the areas and the times of direct and indirect handling of 99mTc. They were compared with the mean values obtained by personnel dosimetry through quartz fibre pocket dosimeters and TLD finger ring dosimeters. The whole body radiation calculated from local measurements for technicians (163 +/- 15 mR/year) (mean +/- SE) and for physicians (260 +/- 15 mR/year) was very low judged by the maximum permissible dose of 5,000 mrem/year and correlated well with those of personnel dosimetry (165 +/- 15 R and 265 +/- 15 R/year respectively). Although local radiation was rather high during generator elution and while preparing radiopharmaceuticals (13 +/- 1.2 mR/h) the radiation exposure to the hands of the radiochemists measured by the TLD finger ring dosimeter was low (2.6 +/- 0.2 R/year). This was attained by consistently using long distance tools in order to avoid direct contact with 99mTc-containing vials and syringes. The most critical point of radiation exposure in our investigation were the finger tips during injection of 99mTc, when syringe shielding was not used (80-130 mR/injection of 10 mCi). Under our conditions this amounts to 330-560 R/year when a total of 40 Ci is injected by the same physician. This by far exceeds the maximum permissible dose of 60 rem/year. The dose can be reduced extensively to only 2-3 R/year when tungsten shielding of the syringe is consistently used.
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