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Biomedical subjects

K Sterling

Publications and source records attributed to K Sterling.

At least 55 records · Page 3Linked to original sources
PubMed1971

Preparation and properties of thyroxine-binding alpha globulin (TBG).

Thyroxine-binding alpha globulin (TBG) in human serum was isolated from Cohn fractions IV-5,6 and IV-4 by (1) chromatography on carboxymethyl (CM) cellulose, (2) gel filtration on Sephadex G-200, (3) chromatography on diethylaminoethyl-Sephadex, (4) a novel procedure of "double-gel" electrophoresis, and (5) preparative polyacrylamide gel electrophoresis. The protein was homogeneous by analytical disc gel electrophoresis, immunoelectrophoresis, and ultracentrifugal analyses (sedimentation velocity and sedimentation equilibrium), and after addition of thyroxine-(125)I showed a constant specific radioactivity on polyacrylamide electrophoresis. The sedimentation and diffusion coefficients were s(20, w), 3.0 x 10(-13) sec, and D(20, w), 8.05 x 10(-7) cm(2).sec(-1), and the molecular weight obtained by sedimentation equilibrium was 36,500. Gel filtration studies on Sephadex G-200 demonstrated that the protein had the same elution volume as that of native TBG in serum, apparently excluding the possibility of a subunit of the native protein. Chemical composition was ascertained by amino acid and carbohydrate analyses. The maximal thyroxine (T4)-binding capacity measured by reverse flow paper electrophoresis was 15,000 mug per g of protein, representing more than 2100 times that of the starting material, or about 5000 times that of whole serum. Based on the molecular weight obtained, the TBG preparation could bind 0.7 mole T4 per mole of protein, suggesting a single binding site. The association constant for T4 was estimated to be of the order of 10(10) by competitive binding studies employing TBG and T4-binding prealbumin (TBPA).

Alpha-Globulins↗
PubMed1970

Conversion of thyroxine to triiodothyronine in normal human subjects.

The conversion of thyroxine to triiodothyronine, previously demonstrated in athyreotic human subjects, has been investigated in normal subjects who were given intravenous injections of purified thyroxine labeled with carbon-14 in ring A and in the alanine side chain. Evidence for the conversion of T4 to T3 was provided by the finding of carbon-14 in the T3 fraction isolated from serums. It is estimated that an appreciable fraction of T4 may be transformed to T3 in normal man.

Carbon Isotopes↗
PubMed1970

The peripheral metabolism of triiodothyronine in normal subjects and in patients with hyperthyroidism.

In order to assess the contribution of 3.3',5-triiodo-L-thyronine (T(3)) to overall thyroid hormone economy, conjoint measurements of the kinetics of peripheral T(3) metabolism and the total concentration of T(3) in serum were made in a group of normal subjects and in a group of patients with hyperthyroid Graves' disease. As judged from the disappearance of trichloroacetic acid-precipitable (131)I from serum after a single intravenous dose of labeled T(3), the following mean values were obtained in the normal subjects: volume of distribution, 43 liters or 0.62 liter/kg; fractional turnover rate. 52% per 24 hr: clearance rate, 22.3 liters/24 hr: and absolute disposal rate, 60 mug/24 hr. In the patients with untreated hyperthyroidism, values for all these functions were greatly increased. After treatment, the volume of T(3) distribution returned to normal but the fractional turnover rate remained abnormally rapid.

Acetates↗
PubMed1970

Conversion of thyroxine (T4) to triiodothyronine (T3) in athyreotic human subjects.

Studies of the possibility that thyroxine (T4) is converted to 3.5,3'-triiodo-L-thyronine (T3) in the extrathyroidal tissues in man have been conducted in 13 patients, all but two of whom were athyreotic or hypothyroid, and all of whom were receiving at least physiological replacement doses of synthetic sodium-L-thyroxine.T3 was found in the sera of all patients, in concentrations ranging between 243 and 680 ng/100 ml (normal range 170-270 ng/100 ml). These concentrations were far in excess of those which would have been expected on the basis of the T3 contamination of the administered T4, as measured by the same technique employed in the analysis of serum. When oral medication was enriched with (125)I-labeled T4 for 8 or more days, labeled T3 and tetraiodothyroacetic acid (Tetrac or TA(4)) were found in the serum to the extent of approximately 2-5% of total radioactivity, as assessed by unidimensional paper chromatography. The same results were obtained with a specially purified lot of radioactive T4 containing less than 0.1% T3 as a contaminant. The identities of the (125)I-labeled T3 and TA(4) were verified by two-dimensional chromatography as well as by specific patterns of binding in serum. The labeled T3 isolated was bound by albumin and by T4-binding globulin (TBG), but not by T4-binding prealbumin (TBPA): in contrast the labeled TA(4) was bound by albumin and TBPA, but not by TBG. To exclude the possibility that the conversion of T4 to T3 was a peculiarity of the oral route of administration, the sera of two additional patients were obtained 48 hr after 7-day courses of daily intravenous injections of a mixture of stable and (125)I-labeled T4. Both stable and labeled T3 were likewise found in these sera. In contrast to earlier experiments in humans in which (131)I-labeled T3 was not definitively demonstrated in serum after a single intravenous injection of (131)I-labeled T4, the present findings are taken to provide conclusive evidence of the extrathyroidal conversion of T4 to T3 in man. These results raise once again the question of the extent to which the metabolic effect of T4 is mediated through the peripheral generation of T3.

Administration, Oral↗
PubMed1969

Determination of triiodothyronine concentration in human serum.

A simplified method has been described for the measurement of triiodothyronine (T3) in human serum. The sensitivity was sufficient for determinations on hypothyroid as well as normal and thyrotoxic sera. The values obtained have been in reasonable agreement with a double isotope derivative assay. The normal T3 concentration in human serum approximates 0.2 mug/100 ml; the mean +/-SD of 31 normal sera was 220 +/-27 ng/100 ml. Elevations were observed in sera from 40 patients with thyrotoxicosis (752 +/-282 ng/100 ml), and diminutions were found in sera from 10 hypothyroid patients (98+/-48 ng/100 ml). In rare instances thyrotoxicosis may be due to elevated serum T3 with normal thyroxine (T4) concentration. The incidence of this condition remains to be determined. In approximately half the cases with low serum T4 after (131)I therapy, the eumetabolic state may be maintained by normal or elevated T3 concentration. From these data and kinetic studies indicating a rapid turnover it may be inferred that T3 rather than T4 may be the more important hormone in health and in disease.

Chromatography, Ion Exchange↗