Nobuhiko Nakazawa

Radioimmunoassay for biopterin in body fluids and tissues

Specific antibodies against l-erythro-biopterin have been prepared in rabbits using the conjugates to bovine serum albumin. The antiserum against l-erythro-biopterin distinguished among l-erythro-tetrahydro- or 7,8-dihydro-biopterin, the other three stereoisomers of biopterin, d-erythro-neopterin, folic acid, and other synthetic pteridines. Using the specific antiserum against l-erythro-biopterin, a radioimmunoassay has been developed to measure the biopterin concentrations in urine, serum, cerebrospinal fluid, and tissues. The conjugate of l-erythro-biopterin with tyramine, 4-hydroxy-2-[2-(4-hydroxyphenyl)ethylamino]-6-(l-erythro-1,2-dihydroxypropyl)pteridine (BP-TYRA), was synthesized and labeled with 125I as the labeled ligand for the radioimmunoassay. BP-125I-TYRA had similar binding affinity as the natural l-erythro-biopterin and was thus permitted to establish a highly sensitive radioimmunoassay for biopterin. The limit of sensitivity of the radioimmunoassay with BP-125I-TYRA as labeled ligand was 0.5 pmol. The total concentration of biopterins, i.e., biopterin, 7,8-dihydro-, quinonoid dihydro and tetrahydrobiopterins, in the biological samples was obtained by iodine oxidation under acidic conditions prior to the radioimmunoassay, whereas iodine oxidation under alkaline conditions gave the concentration only of the former two. Biopterin in urine could be measured directly using 1 μl of urine, but a pretreatment with a small Dowex 50-H+ column was required for serum, cerebrospinal fluid, and brain tissues.

Radioimmunoassay for neopterin in body fluids and tissues

Specific antibodies against D-erythroneopterin have been prepared in rabbits using a conjugate of D-erythroneopterin to bovine serum albumin (D-erythroneopterinylcaproyl-bovine serum albumin). The antiserum distinguished D-erythroneopterin from other pteridines, i.e., three stereoisomers of neopterin, L-erythrobiopterin, folic acid, xanthopterin, and four other synthetic pteridines. Using this specific antiserum, a radioimmunoassay for D-erythroneopterin has been developed to measure the neopterin concentrations in urine and tissues. The conjugate of D-erythroneopterin with tyramine (NP-Tyra) was synthesized and labeled with 125I as the labeled ligand NP-[125I]tyra for the radioimmunoassay. The minimal detectable amount of neopterin was about 0.1 pmol. The concentration of total neopterin (neopterin, 7,8-dihydroneopterin, quinonoid dihydroneopterin, and tetrahydroneopterin) in the biological samples was obtained by iodine oxidation under acidic conditions prior to the radioimmunoassay, and that of neopterin plus 7,8-dihydroneopterin by oxidation under alkaline conditions. Total neopterin values in human urine obtained by this new radioimmunoassay showed a good agreement with those obtained by high-performance liquid chromatography with fluorescence detection. With rat tissue samples which contained very low concentrations of neopterin as compared to biopterin, biopterin was simultaneously determined by our previously reported radioimmunoassay, and neopterin values were corrected for the cross-reactivity (0.1%). The neopterin concentrations obtained by this method agreed with the values obtained by the radioimmunoassays for neopterin and biopterin after their separation by high-performance liquid chromatography. This very small amount of neopterin, as compared with biopterin, in rat tissues could not be determined by high-performance liquid chromatography-fluorometry alone due to the masking of the neopterin peak by a large biopterin peak.(ABSTRACT TRUNCATED AT 250 WORDS)

A new direct solid-phase radioimmunoassay for carcinoembryonic antigen without pretreatment of serum samples.

We examined some fundamental conditions for establishing a new simplified radioimmunoassay system for CEA. The system consists of antibody-coated plastic beads and radiolabeled tracer antibody. The reactivity of this system with several purified CEA preparations can vary due to differences in the nature of antibody preparations used either for coating beads or for tracer antibody. Among purified CEA preparations, we also found some differences in reactivity with a given immobilized antibody preparation. The assay system that resulted, referred to as bead-direct-RIA, needs neither pretreatment of serum samples nor centrifugation in any of its steps, and has a wide assay range, measuring CEA concentrations of 1-300 ng/ml using only 50 microliters of a serum sample. Its accuracy, reproducibility, dilution effect, and analytical recovery proved the reliability of this method. The mean value +/- S.D. for 48 normal adults was 2.5 +/- 1.0 ng/ml. It was found by comparative studies that the Z-gel method of Hoffmann-La Roche generally gave the highest values, the antibody-disc method of Dainabot gave the lowest, and the values by bead-direct-RIA fell between those of the 2 other methods and correlated well with either value. Follow-up studies on patients with malignancy indicated that the values by bead-direct-RIA fluctuated in parallel with those by Roche and Dainabot kits.

Affinity for a Malignant Tumor and Organs of 99mTc-citrate Complex

99mTc-citrateは99mTCO4-を還元剤で還元しておいて, これにクエン酸を結合させるものであるが, 還元剤にSnCl2を用いた場合とFeCl3-アスコルビン酸を用いた場合とNaBH4を用いた場合で生成した99mTc-citrateの化学形は互に異なることが推定された。これを吉田肉腫結節をもったラットに静注して瘍腫親和性を調べたところ, SnCl2で還元して作った997 mTc-citrateが他の2つの還元剤で還元して作った99mTc-citrateよりも好成績をおさめ, 比較のために行った99mTc-bleomycinに比べてややすぐれていることがわかった。この結果から99mTc-citrateは臨床的に腫瘍スキャニングに使用しうると考えられた。またこの化合物はきわめて速やかに尿中に排出された。