DISTRIBUTION OF RADIOACTIVITY IN RATS INJECTED WITH L-14C METHIONINE AS STUDIED BY WHOLE BODY AUTORADIOGRAPHY

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1 DISTRIBUTION OF RADIOACTIVITY IN RATS INJECTED WITH L-14C METHIONINE AS STUDIED BY WHOLE BODY AUTORADIOGRAPHY P. Benard, S. Durand To cite this version: P. Benard, S. Durand. DISTRIBUTION OF RADIOACTIVITY IN RATS INJECTED WITH L-14C METHIONINE AS STUDIED BY WHOLE BODY AUTORADIOGRAPHY. Annales de Recherches Vétérinaires, INRA Editions, 1980, 11 (2), pp <hal > HAL Id: hal Submitted on 1 Jan 1980 HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

2 DISTRIBUTION OF RADIOACTIVITY IN RATS INJECTED WITH L- 14 C METHIONINE AS STUDIED BY WHOLE BODY AUTORADIOGRAPHY P. BENARD S. DURAND Ecole Nationale Vétérinaire, Laboratoire de Radioéléments et d Etudes Métaboliques, 23, chemin des Capelles, Toulouse Cedex, France. 2 Unité de Recherche 101, INSERM, H6pital Purpan, Toulouse Cedex, France. Résumé ÉTUDE PAR AUTORADIOGRAPHIE MACROSCOPIQUE DE LA DISTRIBUTION DE LA RADIOACTIVITÉ CHEZ DES RATS AYANT RECU LA L-&dquo;C METHIONINE. - La&dquo; C-L méthionine est donnée à des rats par voie intrapéritonéale. La dose est de 2,7 mg.kg - et la radioactivité injectée de 100!Ci.kg-. L autoradiographie est réalisée sur tout l organisme du rat. Les plus hautes activités sont localisées dans le foie et le pancréas. Dans le foie il y a accumulation dès la 2e heure après l injection. Dans le pancréas les portions endocrines et exocrines sont marquées. Tous les autres organes sont radioactifs mais les plus fortes activités sont trouvées dans les tissus à haut turn-over protéique (glandes, moëlle osseuse, rate). Ceci suggère que la méthionine est rapidement incorporée dans les protéines et explique la persistance de la radioactivité dans l organisme de rats injectés avec cet amino acide. An excess of methionine in the diet induces severe pancreatic damages and produces necrotic changes (Boquist, 1969) and distortion of acinar architecture (Kaufman et al., The degenerative changes of this organ which are observed include atrophy of acini with replacement by fibrous and adipose tissues (Klavins and Johansen, 1965). The same modifications are described with ethionine which is an ethyl analogue of methionine (Farber and Popper, 1950 ; Goldberg et al., 1950 ; Stekol, 1965). Before studying the action of these compounds on pancreatic enzymes, we started first with an investigation of their metabolism using 4 C labelled compounds. The first step of this metabolic study has been performed by autoradiography (Ullberg, 1954), a technique which allowed us to register radioactivity in the whole body of the animal. This was necessary as no reports deal with this subject. The fate of several amino acids has been already studied by this technique but did not take methionine into consideration (Masuoka, 1973). Radioactivity is incorporated in the pancreas and the enzymes of pancreatic juice when S S-labelled methionine is injected to mice (Hansson, 1957) and this has been confirmed by autohisto-radiography (Leblon et al., Moreover, a high pancreatic uptake has been reported for another analogue of methionine, selenomethionine (Hansson and Jacobsson, 1966), a compound now being used in nuclear medicine for pancreatic scanning (Blau and Bender, 1962 ; Sodee, 1964). This paper presents results obtained by whole-body autoradiography in rats injected

3 - 20 with L 14 C-methionine and compares these data to those concerning ethionine (Durand and Benard, 1979). Materials and Methods. L 14 C methyle methionine was purchased through the Commissariat I Energie Atomique (Saclay, France), with a specific activity of 53 mci.mm -. For each tube, the crystallised preparation was dissolved with isotonic sodium saline solution. The final activity was 50 flci.ml - 1. Male Sprague Dawley rats weighing grams were housed separately. All the animals were given intraperitoneally 2.7 mg.kg - the activity thus delivered being 100 /1Ci.kg - 1. They were sacrificed 5 min, 30 min, 2 h, 6 h, 24 h, 48 h, 72 h and 96 h after the injection. All the ariimals were sacrificed by ether anesthesic. They were then frozen directly on a microtome stage by a rapid immersion in a freezing medium composed of methanol and solid carbon dioxide. A 10 % aqueous solution of carboxymethyl cellulose which formed a firm support all around the animal when frozen, was used as a mounting medium. Whole body sections were then performed with a PMV 450 semi-automatic microtome according to Ullberg s technique ( Before the section was taken, adhesive tape was fixed on the surface of the animal to be sectioned. Then, the microtome stage was automatically moved and a 20 /1m thick slice was obtained. After the sections had been collected they were dried by storage overnight at C in the cryostat. The dried sections were then pressed directly against a single coated X ray film (Kodak Kodirex) in a light tight bag stored at - 30 C. At the end of exposure (one month), the section and the film were separated. The former was stained

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5 (Mayer s haematoxylin) for histological examination ; the latter was developed, fixed and rinsed. All these operations were performed in well defined and controlled conditions and all the autoradiograms could therefore be compared. Results. Results are presented in table 1 and figure 1. Blood. Radioactivity in the blood stream was highest in animals sacrificed 5 min after the injection. It decreased quickly with time and was low after 30 min and at all other times. Pancreas. Five minutes after the treatment (fig. 2), this organ contains a mean radioactivity which is however higher than the one detected in the blood. Then, on animals sacrificed later we notice an accumulation of radioactivity in this organ. Thirthy minutes after the injection, the pancreas is the most labelled organ of the body (fig. 3). The maximum of the pancreatic fixation seems to occur between 30 min and 2 h. On animals sacrificed later, this organ contains always an activity which is higher than the one detected 5 min after the injection. Liver. The kinetics of the fixation of radioactivity in this organ can be described as follow. First there is an accumulation of &dquo; C from 5 min to the second hour after the injection of the labelled compound. Then we observe a decrease till the twenty fourth hour. At this time, the hepatic radioactivity is the highest of the body. In animal sacrificed later there is a slight decrease of activity so that 96 hours after the injection, the hepatic radioactivity is about the same than those detected in most of the organs. Kidney. The kinetics of the radioactivity is very comparable to the one described for the liver. However, the kidney activity is lower in the first time after the injection. Then, from the 24 th to the 96 th hours after the treatment, the kidney radioactivity is comparable to the hepatic one.

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7 In this organ, the distribution of radioactivity is homogeneous in all the histological structures. Miscellaneous. Many other organs are fixing radioactivity in rats injected with &dquo; C methionine : the eye (fig. 4), several glands : thyroid (fig. 5), hypophysis (fig.6l, testicles and epididymis (fig. 7) salivary glands (fig. 8), thymus, Harder s gland, the bone marrow, the spleen (red pulp). In all these organs, we find an uptake which occurs from the 30 th min to the 96 th h after the injection. In the brain and the spinal chord, the level of radioactivity is lower than the one detected in all the other organs. Finally, no radioactivity is found in the digestive tract. Discussion. From the above results, it appears that the absorption of radioactivity is rather slow when &dquo; C methionine is injected intraperitoneally as we found in the abdomen a high activity which persists about 30 min. From a kinetics point of view, the results suggest that blood radioactivity decreases quickly after the injection and then a weak activity is always detectable over four days. This could suggest a fixation of radioactivity on plasma proteins. When considering the tissular distribution, several comments can be discussed. For most the organs, there is first an accumulation of radioactivity and then a slight decrease. However, on animals sacrificed after the 24 th h, the activity detected in all the organs is always persistant to a rather high level. This is

8 true till the 96 th h after the treatment. One exception to this fact concerns the central nervous system in which the activity is always lower than the one registered in all the other organs. This must be a consequence of the blood brain-barrier effect. If we compare these data to our precedent results concerning ethionine (Durand and Benard, 1979), we find a real difference. With the ethyl analogue of methionine, we reported a decrease of radioactivity in all the body which occurs till eight days after the injection. These different results suggest that the ethyl analogue is not probably converted in the rat body to the natural amino acid, methionine. In several organs, there are important differences in the uptake of radioactivity when considering ethionine and methionine. With the natural aminoacid, there is in the first two hours after the injection a fixation in the pancreas ; on animals sacrificed latter the level of radioactivity in this organ is not so high. There is a strong difference between methionine and ethionine for the pancreatic uptake as we have described, with the ethyl analogue an important accumulation of radioactivity in this organ (Durand and Benard, 1979). However, these results confirmed that methionine is incorporated into the pancreas as demonstrated in the cat (Wheeler et al., 1974). Another particular difference concerns the specific distribution over the kidney. With ethionine it was described a very high fixation of radioactivity in the inner part of this organ which seems to be the medulla (Durand, 1979). With methionine, the distribution of radioactivity in the kidney is homogeneous, no part or this organ accumulate radioactivity. Moreover, there is no decrease of activity as previously reported with ethionine. In the eye we have found a mean uptake of radioactivity in both the envelops and the lens. However this is not as important as the one described with ethionine, particularly in the lens. Finally several differences between the two compounds concern the distribution in different organs such are glands, skeleton, muscles, etc. We find a higher uptake in all these organs on animals injected with methionine than on those injected with ethionine. All these data suggest clearly that ethionine and methionine metabolisms are rather different. We can conclude that in the rat body ethionine is not converted to the natural amino acid analogue as the kinetics of the distribution are very different and as we found a persistent activity in all the body on animals injected with methionine, suggesting its incorporation into proteic structures. Accepted for publication January 3rd Acknowledgments. We are indebted to Pr A.G. Rico and Pr L. Douste-Blazy for their valuable advice. Summary 14 C-L methionine was given intraperitoneally to rats. The delivered dose was 2.7 mg.kg - 1and the injected activity was 100 /1Ci.kg - -. Whole body autoradiogaphy was performed on all rats. We noted the highest uptake of radioactivity in the liver and the pancreas. In the liver, there was an accumulation of radioactivity which occurs in the two hours after the injection. In the pancreas, both exocrine and endocrine portions were labelled. All the other organs were labelled but the highest activities are found in high protein turn-over tissues (glands, bone-marrow, spleen). This suggests that methionine is rapidly incorporated into proteins which can explain the persistence of radioactivity in the body of rats injected with this amino acid. References BLAU M. BENDER M.A., Se 75 selenomethionine for visualization of the pancreas by isotope scanning. Radio%gy 78, 974. BOQUIST L, The effect of excess methionine on the pancreas. A light and electron microscopic study in the chinese hamster with particular reference to degenerative changes. Lab. lnvest., 21, 96.

9 . died DURAf!ID S., Action de I éthionine sur Ie pancréas du rat. Modification d activité d une phospholipase A non s!cr!toire. Th. Doct. Sci. Toulouse, 181 pp. DURAND S., BENARD P., Whole body autoradiographic study of the distribution of radioactivity in rats given (14 C 1-2 ethyl) L ethionine. Toxicol. Appl. Pharmacol. In press. FARBER E., POPPER H., Production of acute pancreatitis with ethionine and its prevention by methionine. Proc. Soc. Exp. Biol. Med., 74, 838. GOLDBERG R.C., CHAIKOFF LC., DODGE A.H., Destruction of pancreatic acinar tissue by DL ethionine. Proc. Soc. Exp. Biol. Med., 74, 869. HANSSON E., Studies on the incorporation of S S -methionine in the pancreas and the enzymes of pancreatic juice. Acta Physiol. Scand., 42, suppl. 145, 65. HANSSON E., JACOBSON S.O., Uptake of S Se selenomethionine in the tissues of the mouse stuby whole body autoradiography. Biochim. Biophys. Acta, 115, 285. KAUFMAN N., KLAVINS J.V., KINNEY T.D., Pancreatic damage induced by excess methionine. Arch. Path.!C/?/ca90! 70, 331. KLAVINS J.V., JOHANSEN P.V., Pathology of amino acid excess. IV Effects and interactions of excessive amounts of dietary methionine, homocystine and serine. Arch. Path. (Chicago), 79, 600. LEBLOND C.P., EVERETT N.B., SIMMONS B., Sites of protein synthesis as shown by radioautography after administration of S 35 labelled methionine. Am. J. Anat., 101, 225. &dquo; MASUOKA D.T., ALCARAZ A.F.,, COHEN M.B., SPOLTER L., Acute distribution of C - aminoacids in mice as determined by whole body autoradiography : adjunct for radiopharmaceutical synthesis. lnt. J. Appl. Rad. Isot., 24, 705. SODEE D.B., Radioisotope scanning of the pancreas with selenomethionine. Radio%gy, 83, 910. STEKOL J.A., Biochemical basis for ethionine effects on tissus. Adv. Enzymol., 25, 369. ULLBERG S., Studies on the distribution and fate of S -labelled benzylpenicillin in the body. Acta Radiol. suppl. 118, 1. ULLBERG S., The technique of whole body autoradiographic study, Science Tools, 2. WHEELER J.E., LUKENS F.D., GYORGY P., Studies on the localization of tagged methionine within the pancreas. Proc. Soc. Exp. Biol. Med., 70, 187.