Ballou, J.E.

Buschbom, R.L.

Dagle, G.E.

McDonald, K.E.

UNT Digital Library

* BNWL-SA-5296 INFLUENCE OF INHALED Ca-DTPA ON THE LONG-TERM EFFECTS OF INHALED PU NITRATE by J . E. Ballou, G. E. Dagle, K. E. McDonald and R. L. Buschbom Batte 11 e ,....-----NOTICE----0 This report was p repared as an account of ~ark sponsored by the United States '?'>vernment . Ne1ther the United States nor the Uruted · States Energy Research and Development Adrrtinistration, nor any of their employees, nor a ny of their contractors, subcontracton, or their employees, makes any wuranty, express or implied~ or assumes any legal liability or responsibility for the accuracy, complctcncw 01 usefulnea of any informa tion, apparatus, product o r proceu disclosed, or rep resents that its use would not infri11gr:. privately owne4 ri~ts. Battelle Northwest Laboratory Richland, Washington 99352 This paper is based on work performed under U. S. Energy Research and Development Administration Contract No. AT(45-l):l830 DISTRIBUTION OF THIS DOCUMENT U!ILIMI"f1 DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. ... '. Influence of Inhaled Ca-DTPA on the Long-Term Effects of Inhaled Pu.Nitrate fiJJ If} j_ :_ _:5),1-s-Jl1.G> (!I);U~-'760'70 i --4 . J. E. Ballou, G. E. Dagle, K. E. McDonald and R. L. Buschbo~ Introduction Biology Department Battelle Pacific Northwest Laboratories Richland, WA 99352 The caltium salt of the chelating agent diethylenetriaminepentaacetic acid (Ca-DTPA) is the recognized drug for use in decorporation therapy for deposited plutonium. · The recommended dosage regimen employs repeated daily administration of 1 gram Ca-DTPA by intravenous drip. Within the last decade or so the chelating .agent has .also been administered by the inhala-tion route since. this drug is readily absorbed from the lung and inhalation avoids the trauma of injection as well as expedites the early administration of treatment without the necessity for hospitalization·. Very little is known about the toxi~ology of inhaled Ca-DTPA except through inference .from a number of studies of the toxicity following other routes of adminis-tration. We hav~ found at BNW that rats tolerate intratracheally instilled C~-DTPA quite well with only minimal histopathologica~ effects at dose levels 10 to 15 times greater ~han the dose administered by inhalation to humans. Intratrach~al doses 20 to 30 times ~reater than the human therapeutic dose induced a transient alveolar cell ~etaplasta that recovered within 2 weeks after treatment. Since si~tlar metapl~stic ,• This work was done' by Battelle, Pacific Northwest Laboratories, for the U. S. Atomic Energ,Y Commission under Contract AT(45-l)-1830. '·' \ -2-. changes in the alveolar epithelium are associated with early stages in the process of plutonium damage in the lung it is of interest to investigate the possible additive effect of inhaled Ca-DTPA on the development and progress of these lesions. This paper reports results in rats exposed to aerosolized Ca-DTPA admin~stered 20 days after inhalation of Pu nitrat~. Chelate treatment wa~ delayed to lessen the efficiency of decorporation thus increasing the possibility of detecting an effect that could be attributed to Ca-DTPA toxicity. Changes in weight gain, mortality and the incidence of malignant lung and bone tumors were observed for the animals ltfe-span. Methods Male Wistar rats were employed in this study, exposed to plutonium nitrate or Ca-DTPA aerosols as indicated in the experimental protocol in Table 1. Sham treatment consisted of simulated exposure to Ca-DTPA, i.e. animals were confined in individual animal holders and placed in the . exposure chamber fur the ~dlfie time pel"iod without generating an aerosol. The plutonium aerosols were generated with a Lovelace nebulizer employing a 0.27 N nitric acid solution containing 70 ~Ci 239Pu/mT. The rats were exposed to a chamber concentration of 88 nCi/1, particle size was 1.043 AMAD with a GSD of 1.730. The rats were exposed nose only for 1 hour and were·then housed in a filtered holding box for 7 days before being tr~nsferred to the regular small animal quarters. Ten rats were sacrificed immediately after exposure to determine the initial lung burden (ILB = 78 nCi, range 51-105 nCi). Additional animals were sacrificed after 30, 60, -3- .. 100 and 150 days to determine lung clearance kinetics and the distribution pattern of plutonium translocated from the lung. Twenty days after plutonium exposure 58 rats were selected for Ca-DTPA treatment and 28 were selected for sham exposure. Chelate treatments and sham exposures lasted for 1 hour and were repeated at weekly intervals. for a total of six treatments. Additional animals were exposed to Ca-DTPA aerosols (70 rats) or sham Ca-DTPA (30 rats) following the same treatment regimen. A group of 99 nontreated control animals completed the study. The·chelate aerosols were generated from a 25% solution of Ca-DTPA in water employing a Retec nebulizer. The chamber concentration was 3.5 mg DTPA/1, the particle size was 4.3 llm MMAD with a GSD of 2.22. The effective absorbed DTPA dose was approximately 3 mg/rat/treatment.· The absorbed dose was assumed to equal that amount of DTPA recovered in urine the firs~ 3 days after DTPA treatment. This dose (7 mg/kg) approximates the human therapeutic dose on a per-kilogram basis assuming about 50% of the drug· is absorbed during human inhalation therapy. · DTPA was ana lyied by the method of Wa 11 ace and Hinton pub 1 i shed in Anal Chim'Acta .[!_: 536..:538 (1970). ·The method is based on the formation of the Fe-DTPA chelate.which can pass through a cation exchange column. whereafter Fe is determined by atomic absorption analysis and the amount of DTPA is determined indirectly assuming a .1:1 molar complex for Fe;..DTPA. In our hands the methodwas satisfa<;tory for analyzing aerosol samples or other fairly pure solutions of DTPA~ In biological fluids such as u~ine however, a fair.ly large and .variable background ·cor.rection was required to account fm~.what appea}·ed to be a natU!·al chelating .substunce ·thut ul5o ., -4-carried Fe through the resin column and led to spuriously high values for DTPA absorption. An alternate method for estimating Ca-DTPA dose based on respiratory parameters and aerosol characteristics suggests a dose of 5 mg/rat/treatment in reasonable agreement with the value determined from urine analysis. The rats were held for life-span study of the long-term biological . effects of plutonium and Ca-DTPA treatment. Each group was weighed at morithly intervals and ~xamined daily for dead or moribund ~nimals. · Animals found dead or sacrificed were subjected to detailed necropsy where 8 major organs and all suspicious les·ions were sectioned for histopathologic exam-ination. Where appropriate, tissues were analyzed for plutonium content (lung, skeleton, liver, tracheobronchial. lymph nodes, pelt and residual soft tissues) using the extraction and liquid scintillation techriique of Keough and Powers (1970). Radiation dose to lung and skeleton was calculated for each plutonium rat us1ng clearance parameters~deter~ined from the retention.of plutonium in animals which died during the course of the experiment as well as those sacrificed specifically to determine retention kinetics. Retention in lung was best described by the sum of 3 exponential functions (Figure 1) while plutonium retention in skeleton was assumed to remain unchanged throughout the animals ~ife-span (Figure 2). Results & Discussion I , Inhalation of Pu(N03)4 or Ca~DTPA at the dose levels employed in this study did.not i~fl~ence weight gain (Figure 3) or time of rle~th (Fig11r~ 4) i . . '; .;.5-15 compared to the nontreated ~ontrols. It is also apparent that the incidence of lung tumors and bone tumors was not significantly different in the treated ~nd nontreated plutonium rats (Table 2). Ca-DTPA did, however, decrease the ·~mount of plutonium ·in the skeleton by about 20% (p = 0.05) and the lung · b~roen· was marginally decreased (p = 0.1). The decrease in plutonium burden W~$ apparently not sufficient to deter the induction of tumors or at least ·the effect was not detectable in this study.· Since the initial deposition of plutonium ranged from 50 to 150 nCi in these rats the marginal effects of therapy could not possibly be seen over this background of variability.· After 614 days the skeleton showed a simfl~r 3-fold range in plutonium. burden further illustrating the difficulties involVed in demonstrating o statistically significant effect of treatment. Variations in the initial lung burden combined with differences in life spanresulted in awide range of radiation dose accumulated by the lung and skeleton in both treatment groups. The dose to lung ranged f1·om 36 to 2000 rads (Table 3). The lowest dose which induced a lung tumor was. 50~60 rads accumulated over 600-900 days. The highest dose to produce a lung tumor was 2000 rads accumulated over 975 days. A single lung tumor was found in a rat exposed only to Ca-DTPA and no malignant lung tumors . were seen in the nontreated controls. The single tu~or with Ca-DTPA can Jil.Qt be assumed to be significant in this study although the normal incidence of malignant lung tumors is known to be quite low 1n the Wistar strain. The dose to skeleton was an order of magnitude lower than the lung d~se (Table 4) and the number of tumors correspondingly less. Only two -6-osteosarcomas were found, one in each gro~p appearing after about 10 rads. and 25 rads accumulated dose to skeleton. Since the dose calculation assumed no loss of plutonium from skeleton during the animals life time the cumulative rad dose may be low by as much as a factor of 2 if, for example, the retention· half-time was 500 days as has been reported in some studies. ·The low incidence of bone tumors is typical of other studies with inhaled plutonium where similar bone doses were accrued. Conclusions Inhaled Ca-DTPA administered to rats in 6, weekly~ one~hour treatments of 3 mg/rat did not effect weight gain or life-span compar~d tn plutonium burdened animals (78 nCi ILB) or nontreated controls. In addition, the drug did. not appear to promote the development of malignant lung tumors and bone tumors in plutonium burden~d rats although one rat exposed only to Ca-DTPA aerosols did develop a malignant lung tumor. This single lung tumor can not be considered significant although the normal incidence of this lesion is quite low. Inhaled Ca-DTPA therapy administered 20 days after plutonium inhalation showed little effect in reducing the lung burden of plutonium. Skeletal deposition was decreased possibly because Ca-DTPA was administered during a time of active translocation of the inhaled plutonium when plutonium may have been available for chelation in the blood. Inhaled Ca-DTPA therapy did not appear to be beneficial in reducing the ~umber of malignant lung tumors or bone tumors in plutonium burdened rats but on the other .hand the chelate did not appear t~promote these lesions. ..... Table 1 · Experimental Protocol Number Treatment of Rats Pu (N0 3 h + Sham Ca-DTPA 28( 8)* Pu(N03)4 + Ca-DTPA 58(12) Sham Ca-DTPA 30 Ca-DTPA 70 Nontreated Controls 100 *Values in parenthesis are number of rats sacrificed to determine.efficacy of Ca-DTPA . .;·· . . . . Table 2 Summary of Long-Term Effects .. Treatment Pu(N03)4 + Sham Ca~DTPA Pu(N03)4 + Ca-DTPA Sham Ca-DTPA Ca-DTPA Nontreated Controls Tumor Incidence (%) Lung Bone 47 5.3 42 2.3 0 0 .1.4 0 0 0 . I Table 3 Pu(N0 3 ) 4 Induced Lung Tumors - Effect of Inhaled Ca-DTPA -· Dose Range Number · Days at Rats with (Rads} of Rats Risk (Ave.} Lung Tumors ' 36-100 5( 1)* 603(888) 1(1) 101-300 13( 3) 555(546) 5(1) 301-500 16( 7) 657(608) 5(3) . 501-1000 8( 5) 714(699) 6(2) 1001-2000 1( 3) 975(641) 1(2) Ca-DTPA 70(30) 604(591) 1 ( 0) Control 99 677 0 * Values in parenthesis are for animals given sham Ca-DTPA exposure. · · ,(; ·.: . Dose Range (Rads) 2-10 11-20 21-30 31-78 Ca:..DTPA Control · Table 4 . Pu(N0 3 ) 4 Induced Bone Tumors - Effect of Inhaled Ca-DTPA -Number Days at Rats with of Rats ~isk (Ave.) Bone Tumors 17( 0)* 470( . 0) l(O) 11 ( 6) 586(593) 0(0) 5( 2) 692(680) O(l) 7(10) 733(653) 0(0) . 70(30) . 604(591) 0(0) 99 677 0 : *Values in parenthesis are for animals given sham .. · ._ Ca-DTPA exposUI·e. 1 l 1 ·~) ~ f'.J' '' •'li i II J:..j-·: .l ;•; ·:t; .. •, ,., ,::1 '.•!: 'iii ';:.; l.::•,::: '·~~---~--~-· :~:~~~:_!~~~'+--'-·~~r·,!_:_i+-!~!_i~~~~~-:!_,j _ __;_-~l·_-+r"-~-+'·-~:~~~~~·~·~--~--~~~~'-'~-~~1 ~~--~--~+~~·--·:..f~~---+-~~~~~~--~--~~~--~--~+-~r-~r---1-----t-------r-~----~ · ,' '· • ,' •1 • ~~. ! ',. • · .. .. 1 1 ' I · i--~--~ • 1 · ' 1 1· ' r: _j ,i!· 'JiJ 'i!'l_l. ~ !".":-:_!,: 1,.·. ;:, •• 1,. :r: ,_i '; .• I I : · • ' 1 ! ; r • ~ I , f I / · I -r : 1 . ' • • : ~ ! : 1 1 I' r!; ). ~-_,·, ' ( "' "' .... l!. "' 'y 0::'11 Iii 3 VH I£L·6££ "' 'O:J H::JS~:J lU ,3;l.:;lrt')>f ::>I ~·lHl.J w.-~o,-1,~35 ':! ' ... 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Influence of inhaled Ca-DTPA on the long-term effects of inhaled Pu nitrate

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Influence of inhaled Ca-DTPA on the long-term effects of inhaled Pu nitrate

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