The ingestion by normal subjects of 3 g of sodium iopodate, which is widely used in routine oral cholecystography, resulted in significant decreases of serum total and free T3 to a nadir on day 4 which averaged 43% and 40%, respectively, below initial mean values. Total and free rT3 increased markedly to a peak on day 3, 244% and 189%, respectively, above initial mean values. Total and free Ti and free T4 index rose to a maximum on day 4, but these changes were not statistically significant. A marked TSH increase was also seen, most evident on day 3. All these changes reverted to baseline values by day 14 at a time when serum total iodide was still markedly elevated. It is concluded that the changes observed after iopodate were not due to alterations in serum binding proteins nor to an effect on thyroid gland by the large iodine component of iopodate, but were consistent with an effect on the peripheral metabolism of T4. Difficulty in ipterpreting routine thyroid function tests may occur for up to 14 days after oral cholecystography with iopodate. Sodium iopodate is a contrast medium commonly used in oral cholecystography. Its chemical struc¬ ture bears some similarity to that of thyroxine (T4) and 61.4% of its weight consists of iodine. Wu et al. (1978) observed the effects of iopodate ingestion for a week and showed that serum 3, 5, 3' triiodothyronine (T3) decreased, 3, 3', 5' triiodothyronine (rT3) increased and T4 increased in euthyroid subjects. Similar changes were observed in thyrotoxic patients excepting that serum T4 decreased. They concluded that iopodate alters peripheral metabolism of T4 and, in thyrotoxicosis, it may decrease thyroid activity also.Because of its widespread use in clinical practice iopodate may commonly complicate the interpreta¬ tion of routine thyroid function tests. We therefore decided to document the magnitude and duration of such interference by observing the effects of oral iopodate on routine thyroid function tests. We also studied the effects on the serum concentrations of total and free rT3, free T3, free T4, thyroid stimu¬ lating hormone (TSH) and total iodide to help elucidate the mechanism of the interference. Subjects and MethodsSix healthy adult male volunteer subjects were studied whose average age was 25 years. Sodium iopodate was given in 3 separate 1 g oral doses between 09.00 and 12.00 h. Similar studies were conducted on two other healthy volunteers given an equivalent oral dose of iodine in the form of potassium iodide. Blood was sampled by venepuncture at 09.00 h on each day of observation namely 10 and 6 days before iopodate, on the day of taking iopodate and on days 1, 3, 4, 7, 14 and 21 after the doses. Samples were taken with minimal venostasis after the subjects had been sitting for 5 min. Serum was stored in aliquots and analyzed soon after the last sample was collected. All samples from each subject were analyzed in the same batch.Concentrations of total T4, total T3, rT» and the TSH were determined by specific radioimmunoassay (RIA) using second anti...
In the kinetic angiotensin-converting enzyme (ACE) method, a practical and optimal buffer is 80 mmol/L borate buffer at pH 8.2 (37 degrees C). A lag phase is detected in the reaction, and a 5-min incubation of substrate and plasma is suggested before the kinetic measurement. The substrate, N-[3-(2-furyl)acryloyl]-L-phenylalanylglycylglycine (FAPGG), concentration is maximized at 1.0 mmol/L and the measurement wavelength is at 345 nm to ensure linearity of measurement. The proposed procedure uses a 1:9 plasma-to-reagent volume ratio. The linear range of the assay extends to approximately 170 U/L, representing a 25% substrate hydrolysis. The FAPGG absorptivity is determined by measuring the difference in absorbance between 1.0 mmol/L FAPGG and the product solutions. The wavelength fidelity is checked by noting the expected absorbance value of the FAPGG solution, and a 1.0-nm deviation from 345 nm alters the absorbance by 15.5%. The precision of ACE assays at approximately 60 and 100 U/L is 3.5% and 2.4% within batch and 2.9% and 2.6% between batch, respectively. The reference interval (2.5th to 97.5th percentiles) is 41-139 U/L, and there is no difference between values for men and women.
Five Merino or Merino X milk-fed lambs, 4.7*10 kg liveweight, were used to study the development of abomasal secretion using betazole HCI as secretagogue. The linear relationships between maximal acid output and liveweight, and maximal secretion of abomasal juice and liveweight were positive, and between maximal clotting activity output and liveweight was negative.
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