Bound Iodine Concentration Research Articles

A water-soluble triiodo amino acid and its dendrimer conjugate for computerized tomography (CT) imaging

Prolonging the circulation of an imaging agent is vital for making it suitable for blood pool (vascular) imaging. Medical applications of vascular imaging include cardiovascular disease, abnormal capillary permeability, and tumor neovascularity. As low molecular weight computerized tomography (CT) enhancement agents are characterized by inconveniently fast clearance, macromolecular compounds (both natural and synthetic) have gained a wide recognition for possessing better characteristics for performing blood imaging tasks. Herein, the syntheses and characterization of a new water-soluble triiodo amino acid, 3-[(N,N-dimethylaminoacetyl) amino]-?-ethyl-2,4,6-triiodobenzenepropanoic acid (DMAA-IPA) and its Starburst PAMAM generation 4.0 dendrimer conjugate, G-4-(DMAA-IPA)37 are described. The applicability of G-4-(DMAA-IPA)37 as a potential macromolecular angiographic CT contrast agent is discussed. The linear relationship between organically bound iodine concentration and CT Hounsfield units has been established thus allowing for quantification uses of CT imaging as well.

Increased thyroxine secretion following administration of dinitrophenol to rats.

1. Feeding male rats 0.2% dinitrophenol (DNP) in the diet caused weight loss, a significant fall in the plasma protein bound iodine concentration, and a rise in the thyroxine secretion rate. Thyroxine concentration was raised in the liver and intestinal tract with contents, reduced in the carcass, and unchanged in the pelt.2. Radio-iodine uptake by the thyroid gland was unchanged but there was a significant fall in the thyroid/serum activity ratio.3. Five hours after tracer radiothyroxine, DNP treated rats had a reduced fraction of dose in the plasma, with raised concentrations in the liver and intestines.4. Fractional turnover rates of radiothyroxine in plasma, liver and carcass were raised in DNP treated animals.5. DNP caused a significant increase in the biliary clearance of radiothyroxine, when measured immediately after administration of tracer and 4 hr later.6. It is postulated that DNP displaces thyroxine from its plasma binding proteins and that the displaced hormone is excreted in the bile. This wastage together with increased demand resulting from DNP induced hypermetabolism results in increased output of thyroxine by the thyroid gland.

Effect of chronic immobilization on the turnover and metabolism of L-thyroxine and thyroid function in the rat.

The effect of immobilization on thyroid activity was studied in rats restrained in hind—limb casts for 17 days, a procedure which resulted in significant muscle atrophy in the casted extremities. Immobilization was associated with increased metabolic clearance of thyroxine due to increased urinary deiodinative and fecal clearances. Although no change was demonstrated in plasma thyroxine—by—column measurements, the serum protein—bound iodine concentration diminished during the period of immobilization. The observed increases in clearances, plasma fractional removal rate, total and hepatic distribution spaces, liver:plasma ratio of thyroxine, and fall in serum protein—bound iodine concentration all appear related to diminished binding of the hormone by serum proteins. The absolute thyroxine degradation, intrinsic cellular hormonal clearance, and isotopic measurements of thyroid function were unchanged. (Endocrinology91: 355, 1972

Increased thyroxine secretion following surgical operation.

Radiothyroxine turnover measurements were made in 10 male patients before and after relatively minor surgery. Thyroxine secretion rate rose significantly from 110±15 μg. per day (mean±SD) pre-operatively to 137±33 soon after surgery, although plasma protein bound iodine concentrations remained unaltered. Plasma activity, following a dose of radiothroxine given prior to surgery, diminished at a single exponential rate, which continued through surgery. A second dose of radiothyroxine, differently labelled and given post-operatively also disappeared exponentially, but in every case the slope was steeper than for the pre-operative dose. The daily fractional disappearance rate rose significantly from 0.11±60.029 pre-operatively to 0.163±0.028 post-operatively.

Observations on the relationship between the maximal thyroxine binding capacities of thyroxine-binding interalpha globulin and thyroxine-binding prealbumin, the serum protein bound iodine concentration and sexual maturity in adolescents.

ABSTRACT The serum PBI concentration and the maximal thyroxine binding capacity for TBG and TBPA were determined in 100 adolescents. The subjects were classified according to sex and degree of sexual maturity. PBI was determined by an autoanalyzer method: Maximal thyroxine binding capacity for TBG fell with increasing maturation in males while TBPA capacity rose in both sexes. The slight changes in serum PBI noted with increasing sexual maturity correlated directly with the slight changes in TBG binding capacity; no correlation between PBI and TBPA binding capacity was observed as maturity progressed.

Effect of dietary iodine on serum inorganic and salivary iodine

The quantitative relationships of the concentration of inorganic iodine (I 127) in serum (SII) and salivary iodine concentration with the dietary iodine intake were studied in 4 normal women living at home and following their usual dietary, work, and recreational habits. Under these conditions SII was found to be directly proportional to the dietary iodine intake on the day the blood sample was obtained. Salivary iodine concentrations and salivary iodine secretion rates were also directly proportional to iodine intake, but the proportionality was linear only at intake levels below 167 μg./day. In addition, SII, salivary iodine concentrations, salivary iodine secretion rates, and salivary protein bound iodine concentrations were determined in 19 subjects during a 5-week period. The frequency distributions of these 4 parameters proved to be lognormal. The implications of the data are discussed.

OBSERVATIONS ON THE PRODUCTION OF GOITER IN RATS WITH PROPYLTHIOURACIL ANDON GOITER PREVENTION1

Rats fed propylthiouracil and injected with sodium-l-thyroxine (1.0 to 2.5 µg. per rat per day) developed goiter in the presence of normal concentrations of plasma protein-bound iodine. At all dose levels of thyroxine, rats fed low residue diets had greater serum bound iodine concentrations than animals fed commercial laboratory chow. Since goiter was found in presence of normal or high bound iodine concentrations, this may mean (a) goiter can develop despitelow plasma levels of thyrotropin under these conditions or (b) plasmaproteinbound iodine may have an abnormal composition or influence in these types of experiments. A method is presented for determination of plasma protein-bound iodine by isotope dilution.