103 ‘ollowingf a.,,| -'°Po. Additionally, in cases where no estimates of (0.7% offi] activity are available, the 742Pb activity gives > In 108.ne indication of the doses to be expected from the propor-Fy.jighter products which follow it in the decayseries. F =\Jeusurements are recorded in Table 38 of the distri11 ton of “1*Pb throughout the organs of 7 rats, lL dog, Th atfeniployed similar to that of Table 35. The results for ected to Fileen and kidney in the one human patient who was Bexamined do not appear to agree very well with the rro-ults from the experimental animals, The reason for thix ix not known. are dis-€ | human kidneys contained 2!*Pb in amounts comly fromfysarinble to those observed in rats (Table 38), a dose Jence offr.t¢ would be obtained which, taking account of the TABLE 40. #2Pb Activities 1n BLoop CELLS OF THOROTRAST PatTIENtTs 3 WEEKS arreR [.V. ADMINISTRATION Thorotrast Patient code % | 83 71 pCi/g cells | | 2122Pb in total blood, % of whole body 48 | 36 24 | 20 48 Mean value_ value | } 28 19 27 | 23 ‘) Based on (1) known 228Th activity injected, (2) assumption of 4% body burden per day excretion of **Ra and 10° exhalation of thoron,®® (3) 2100 g blood cells in whole body. TABLE 41.) Activity Ratios 1n BLoop FROM ADULT BEAGLES INJECTED WITH #°Th [AFTER STOVER ET AL.(5)](#) 28Th Cells Plasma 3 appre-Fticnt= are long since past their youth. Therefore, it is ont-thatisienificant that although lead (and bismuth) comPov may produce renal damage in children,'****) simetrysacli:lt renal tissue appears to be relatively insuscepti3 and yf}, The inference that the adult kidneys do not con- 212Pb activity, injected, ml 224Ra | 22Pbh | 212 Bi ? ? 100 90 0.21 5 <2 10 ‘) The figures are normalized to refer to a volume of blocd in which the 2“2Pb activity of the cellular fraction is 100 (arbitrary units). The activities (same arbitrary units) of the other nuclides in the cellular and plasma fractions are then given by the numbers in the table. based ‘partly on additional arguments, are presented Fhich concentrations in the kidneys only in the young fand young-adult animals.*) » Ax a consequence of these complicating factors, the Fticns of the distribution of 2!2Pb in a Standard Man P(Vable 39) are, therefore, based solely on the results ffor patient code number 85. Even here the numbers are subject to large uncertainties. More reliable estimates, od cells F TABLE 39. ope Tissue Organ DISTRIBUTION OF #2Pb IN Man WOnsen 6.778 weight in standard - Chom vo CHr organ (CH/ man, kg Table 38) ; Laver : Spleen Kidney Tung Cortical bone 29 Red bone marrow — 9 F -§ Blood cells " ~ | 1.7 100 0.3 8 0.15 1.0 7.0 50 35 8 3.47) °§=6170 | 7.5 2.4 35 56 45 2.0 0.6 9.3 14,9 1.5 30 45 ' 12.0 2.1 29 61 | 16.2 377 160 Percent only of those organs listed. Other soft tissues Pienably contain a significant activity of 22Pb. later in Table 51. In addition to the autopsy samples referred to in Table 40, several blood samples irom short-term Thorotrast patients were examined at 3 days, 1 week and 3 weeks after administration. 74*Pb was found in the cellular fraction of the blood, and was indeed the only radionuclide whose presence in vzvo could be deduced with any certainty. The results of the measurements at three weeks following administration are listed in Table 40. The actvities of 7!*Pb in the blood at three days and seven days following administration were lower at values, respectively, of about 18% and 19% of the whole-body content. The activities in the blood of ??°Bi, and, with a larger uncertainty, those of *4Ra and **8Th, can probably be inferred approxi- mately from the data of Stover et al.) on the metabolism of 778Th in beagles (Table 41). One of us (HFL) obtained 30 ce of whole blood from a Thorotrast case through the kindness of A. Grillmaier. This case had a whole-body content of 15 X 1077Ci *8Ra and 1.3 x 10-*Ci *8Th. The 28Th content in this blood sample was determined by the very sensitive method of Stehney,‘?® and the **8Ra was determined from the regrowth of **°Th over a twoyear period. The estimates of 4 + 3* x 107'*Ci 28Th/g and 4 + 15* x 10-1®Ci *8Ra/g are not sta* 00% confidence interval.