Biodistribution of 95Nb and 182Ta in tumor-bearing animals and mechanisms for accumulation in tumor and liver.

Abstract

The biodistribution and binding substances of 95Nb and 182Ta were investigated and compared with other nuclides using tumor-bearing rats and mice. Retention values of 95Nb in tumor tissue were greater than those for 67Ga-citrate, while those for 182Ta were similar to those for 67Ga. The values for these nuclides in the liver and spleen were much smaller than those for 67Ga. However, the values for blood and some soft tissues were much greater than those for 67Ga. The concentrations of 95Nb and 182Ta were more dominant in the connective tissue (especially inflammatory tissue) than in the other categories of tumor tissue. These nuclides accumulated rapidly into the mitochondrial fraction (containing lysosome) of the liver, reaching about 50% after 48 hours, but these nuclides existed relatively uniformly in the tumor cells. The main binding substance of these nuclides in the above tissues was the acid mucopolysaccharide whose molecular mass exceeded 40,000 daltons. Radioactive niobium can be a potential tumor imaging agent. Among radioactive niobiums, 95mNb has physical characteristics (half-life 90 hours, IT decay, 234-keV energy of 100% abundance) suitable for clinical imaging study.

Biodistributions of radioactive bipositive metal ions in tumor-bearing animals

“…However, the values of 65Zn for tumors are similar to those of 67Ga, which is widely used to detect tumor lesions (Ando et al 1985). Generally speaking, retention values of these bipositive metal ions were smaller than those of metal ions described above (Ando et al 1982(Ando et al , 1983(Ando et al , 1985(Ando et al , 1987bAndo & Ando 1986, 1990.…”

“…To date we have reported as follows: large amounts of 67Ga (Ando et al 1985), 111In, 169yb (Ando et al 1982), 167Tm (Ando et al 1983), 46Sc, 51Cr (Ando et al 1987b), 95Zr, 181Hf (Ando & Ando 1986), 95Nb and lS2Ta (Ando & Ando 1990) are concentrated in the mitochondrial fraction (containing lysosome) of liver, and lysosomes play an important role in the liver concentration of these nuclides. Quite large amounts of 46Sc, 51Cr, 95Zr, lalHf, 95Nb and 182Ta are concentrated in the mitochondriai fraction (containing lysosome) of Yoshida sarcoma and Ehrlich tumor, but 67Ga, H~In, 169yb and 167Tm are not concentrated in the mitochondrial fraction of these tumors.…”

“…We had also been investigating the behavior of radioactive metal ions in animals to offer data which contribute to development of radiopharmaceuticals and to health physics and hygiene. To date the biodistributions of 2~ (Ando et al 1987a), alkaline metals (Ando et al 1988), 67Ga (Ando et al 1985), lllln, 169yb (Ando et al 1982), 167Tm (Ando et al 1983), 46Sc, 51Cr (Ando et al 1987b), 95Zr, 181Hf (Ando & Ando 1986), 95Nb and 182Ta (Ando & Ando 1990) in tumor-bearing animals and mechanisms for accumulation in tumor and liver have been investigated by us. The cations of these nuclides were positive monovalent (2~ 22Na+, 42K+, 86Rb +, 134Cs+), trivalent (67Ga3+, lllln3+, 169yb3+, 167Tm3+, 46Sc3+, 51Cr3+), quadrivalent Address for correspondence: A. Ando, School of Allied Medical Professions, Kanazawa University 5-11-80, Kodatsuno, Kanazawa 920, Japan.…”

Relationship between the biodistributions of radioactive metal nuclides in tumor tissue and the physicochemical properties of these metal ions

“…14-16 In the case of 51 Cr, 181 Hf and 182Ta, very similar results were obtained. 13,15,16 These elements became extremely concentrated in inflammatory tissue. Figure 1 shows the result for 65Zn and 103 Pd.…”

“…We summarized the biodistribution of 54 elements and 66 compounds in tumor bearing animals as already reported.5.6 On the other hand, we have been investigating the biodistribution of radioactive metal nuclides in tumor tissue by macroautoradiography. 7,8,[13][14][15][16][17] In this study, metal organic compounds such as 67 Gacitrate and 95Zr-oxalate, were classified as inorganic compounds because these metal nuclides were dissociated from these metal organic compounds in the body after intravenous (IV) or intraperitoneal (IP) administration. To date we have investigated the biodistributions of 17 elements in tumor tissue and examined the relationship between the accumulation in tumor tissue and the properties of these metal compounds.…”