The accumulation of rubidium and cesium in altered human thyroid

Instrumental Neutron Activation Analysis (INAA) was applied to several huma n thyroid samples that were collected in 72 patients. Different diseases af fected the thyroid: Multi Nodular Goitre (MNG), Chronic Lymphocytic Thyroid itis (CLT), Follicular Adenoma (FA) and Thyroid Cancer (TC). Thyroid sample s and SRM from bovine liver (NIST BL 1577b) were irradiated by thermal neut rons (Phi=2x10(14) n cm(-2)s(-1)) for 40 h and gamma-ray spectrometry was a pplied to measure Rubidium (Rb-86) and Cesium (Cs-134). Short term irradiat ion (thermal neutrons with Phi=10(13) n cm(-2)s(-1) for 60 s) was applied t o measure Potassium (K-42) in thyroid samples and in a chemical standard. T he distributions of elements in normal tissue were compared to those in alt ered tissues and also among the different group of patients. Moreover, cell fractionation was carried out in order to investigate the accumulation of Rb and Cs within major cell components. Three orders of magnitude different iate the concentrations of Cs (ppb range) and of Rb (ppm range) in the thyr oid. An increase of Rb and Cs concentrations were measured in altered with respect to normal thyroid tissues: in particular, significantly higher mean values of Rb and Cs were present in MNG, in TC and in FA thyroids with the greatest difference in the last. Also the mean concentrations of Potassium were significantly higher in altered than in normal tissues. The relative concentrations of Ph and Cs were positively and significantly correlated in all the samples (R-P 0.76, p<0.001, n=144). Also Potassium was directly co rrelated with Rubidium (R-P=0.74; p<0.001, n=36) and Cesium (R-P=0.37; p<0. 05). The great part of Rb was lost during cell fractionation and Cs was mai nly found in the nuclear fraction and only partially in microsomal and mito chondrial fractions. We suggest that a common non competitive mechanism is likely to mediate the uptake of these alkali elements that accumulate withi n normal to proliferating thyroid tissues.