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Location of iron and porphyrin in the liver in porphyria cutanea tarda
Acta histochem, Bd. 63, S. 168-176 (1978)
University of Minnesota, Medical Research Unit, Northwestern Hospital, Minneapolis, U.S.A.
Location of iron and porphyrin in the liver in porphyria cutanea tarda By ZBYSLAW J. PETRYKA, NIKOLA D. Kosrron and G. JEELANI DRAR1 ) With 2 figures (Received May 9, 1978)
Summary Porphyrin and iron distributions in the liver biopsies of patients with Porphyria cutanea tarda (peT) were investigated by comparison of eomposite photographs from fluorescence microscope and after iron stain. Three distinct areas are visible: 1. red fluorescent areas with porphyrins; 2. blue areas corresponding to iron; 3. areas with neither iron nor porphyrin. The areas with iron or porphyrin do not overlap, therefore, this experiment indicates lack of direct correlation between iron and porphyrin distribution in liver" of Pf"]' patients.
Introduction The clinical manifestations of Porphyria cutanea tarda (POT) are directly related to excessive production of uroporphyrin in the liver (2, 9, 20). Hypersideremia and hepatic siderosis are found in a high percentage of patients with POT (6, I l , 12, 17), however, the incidence of POT among alcoholics (4, 5, 8) is quite low. In various studies in many countries, this incidence is in the range of 1 to 4% (5), which in itself, suggests a genetic factor (3). In liver biopsies from POT patients, it has often been observed that the liver contains an excess of both iron and porphyrin (6,9, Ll , 12, 17). This suggested a direct correlation between hepatic iron overload and porphyrin overproduction in the hepatocytes (6,9, l l , 12, 17). Also, as is well known, treatment by multiple phlebotomies regularly brings about biochemical and clinical remission regardless of the presence of increased stainable iron in the liver (13). Since analysis of the liver provided evidence for iron and porphyrin excess (6, l I, 12, 17), it has generally been assumed that the iron and porphyrin occur in the same areas in the livcr (Il). No report has been found of simultaneous study of the porphyrin and iron locations (1). This common assumption of the presence of iron and porphyrin in the same hepatocytes (17), or even in closely contiguous liver cells, is not confirmed by microscopic studies. The microscopic studies were reported for rats fed with hexaI) Present address: Medical college of Wisconsin Milwaukee County General Hospital, Gastroenterology Section, Milwaukee, WI 53226.
Iron and porphyrin in the liver
169
chlorobenzene and iron (18, 19); hexachlorobenzene induced porphyria in rats serves, at least in some respects, as a model for POT (7, 9,10, 15, 16, 18, 19). The authors (18, 19) have found the porphyrins in the hepatocytes without iron, or where stored iron was depleted to such an extent as not to exhibit iron by staining. This finding represents a discrepancy in respect to the accepted assumption of porphyrins and iron in the liver. In cases of POT precipitated by estrogen (8, 14) without iron in the liver (2, 8), increased porphyrin production was obviously not related to stainable hepatic iron.
Materials and Methods In the present study, tho loc ations of iron and porphyrin wore determined in liver biopsies of four patients having PCT. The informed written consents were obtaino.I from all the patients after the nature of the procedure had been fully explained to them. PCT was diagnosed by the characteristic symptoms and clinical findings supported by the presence of 8- and 7-COOH porphyrins in urine and feces, and prominence of isocoproporphyrin in feces. Th3 latter group of porphyrins is highly characteristic of PCT. Liver biopsies were done with a Menghini neo.lle (0.4 mm bore). The specimens were instantly frozen on dry ice and 5 flm thick frozen sections were prepared. In patient # I, in which the biopsy was kept for two hours at room te.nperature, a diffusion of fluorescence was observed. The usually well clelinoated, intense fluorescence became diffuse. In another patient, # 2, absolute ethanol fixed sections were also prepared; they were compared microscopically with frozen sections. The unstained specimens were observed by visual microscopy and in a Reichert fluorescence microscope with 400 nm exciting light. The location of fluorescence was recorded prior to the iron staining. Color slides and white prints of tho red fluorescence were prepared. For tho former, a Kodak G15 filter was used, and for black and white, two filters, Kodak G 15 and G25. With this combination, the red fluorescence is photographed as white. Thc whole specimen, often 6 to 7 mm long and 1 to 2 mm wide, was photographed piece by piece, resulting in 20 to 30 fragmentary photographs for each biopsy. These, when place side by side, reproduced the general morphology of the section and the locations of red fluorescing areas. After photographing the fluorescence, the same sections (fragments) were stained for iron (standard iron stain). After iron staining, the red fluorescence disappears. Iron stained slides were photographed with the same m'3,:;nification, fragment by fragment, using a Kodak Gl5 filter. The prints placed side by side reproduce the general topography of the specimens, and they were compared with the same areas showing red Fluorescence. The various locations of porphyrin (red fluorescence) were compared with that of iron (blue spots after iron stain). Representative areas of the photographs art! shown in Figs. 1 and 2.
Results and Discussion Examination of liver specimens from peT patients permitted us to conclude that iron and the red fluorescence of porphyrin were located in different areas. Fluorescence in the frozen sections (Fig. 1A) was more diffuse, broader, and not as intense as in absolute ethanol fixed sections (Fig. 2A). In all specimens investigated by us, there were definite areas of red fluorescence. Red flucrescence, related to porphyrins, has a tendency to concentrate in selected areas in the liver. Therefore, the liver section in the fluorescence microscope looks "patchy" with red fluorescence in certain sections and large areas without red fluorescence. A patchy distribution is also observed for iron, the concentration and distribution of iron granules is uneven through the 12
Acta histochem. Bd, 63
170
Z. J.
PETRYKA,
N. D.
KOSTleR
and G. J .
DIIAR
Fig. 1. Li ver biopsy from p el' pati en t s - frozen sect ion s : A and B
=
:j:I: 1 ; A land B!
= :\:I: 2;
A. In fluorescence mi eroscopo (details d escribed in " Meth od s"), the whi te areas correspond to red fluorescen ce of porphyrin ; they a re indicated b y arrows a nd letter " P" . B . In t ra ns mit ted light in mi croscop e aft er iron stain, the black sp ots co rres p on d to stainable iron, indica t ed by arrows and letters "Fe " .
Iron and porph yr in in the li ver
12'
171
172
Z. .J.
P E T H': K.\ ,
X. D .
I~ (J S Tl cH anti
G. J .
)) HA R
I r o n a nd pnr ph y rin in th o liv er
173
A
F ig . 2. Li ver biopsy sec t ion fr om p e T p atient ( # 2) - fixed with absolut e e th a nol. A . I II flu or escence mi cr oscop e, th e wh it e a reas corresp on d t o red f'l uorescen ce of porphyrins ; they a re indi cated b y arrows and let ter " P " . B . I n t ransmitt ed light in m icroscop e after iron st a in , the bl a ck spots corresp on d to stainable iron in d ica ted b y a rrows and letters " F e".
liv er . No differences are observed in frozen vs ethanol fix ed sect ions. There are parts of the liver where a large con centration of iron is noted and ot her areas where there is no ir on , or very little. This ca n be seen in iron stain of fr ozen sections (Fig. IB) and absolute etha nol fix ed sect ions (Fi g. 2B). The irregularities of fl uoresce nce already mentioned are also observed with iron staining . Th e ph otographs of red fluorescence of liver specimens wer e compared with ph otographs of iron stain from the sam e secti on s. A comparison of t he location s of iron in relati on to loca ti on s of porphyrin, was possibl e (Figs. 1 and 2). J n frozen and et hano l fix ed sect ions, large areas of liv er do not contain eit her fluorescence or ir on. Iron is found in th e ar eas where red fluorescen ce is minor or lacking, a nd vice versa . Ther efor e, sections fro m t he liver biopsies
174
Z. J.
PE'I'RYKA,
N.
D.
Kosrrcrr and G. J.
DHAR
Ir on and p orph yrin in th e liver
175
can be subdivided into three maj or areas, one where porphyrin was located (marked with " P" in li'igs. 1 a nd 2), a no t her sect ion where iron was located (marked with " Fe" in Figs. I a nd 2), and a reas with neither iron nor fluorescen ce in significant amount. This subdivision ha s also bee n ob ser ved in rats fed R CB (18, 19). Again, in et ha nol fixed sect ions , red flu or escen ce is bette r defined and areas with porphyrins were more concentrated. Th e diffusion of red flu orescen ce into slight ly pink areas , with ordinary fi xation , was not ob served . The cells a nd location of porphyrin within the cells is clearly visible. The et ha nol fix ation did not affe ct iro n sta ining, which remained ex ac t ly the sa me as in the frozen section (Fi gs. IB and 2B) . Iron loca tions in both froz en a nd etha nol fix ed sections were t he sa me. Th e relative location of iron and porphyrin ca n be seen in Figs. 1 a nd 2 where porphyrins ar e indicat ed by letter " P", iron by letter s " F e" . The ba sis of the differing location of porphyrin and ir on is not clear. It could be theoriz ed that iron located in the liver affects the enzymes t o in crease heme formation, and through negative feedba ck , red uces further porphyrin format ion . If this were true, t he a mount of porphyrin which would be seen migh t be small or negligible. In t he ar eas with cells loaded with porph yrin there would be, if not a defici ency of iron, at least norm al level of iron and th e porphyrins would presumabl y not accumulate there. R ow the division comes a bout betw een cells accumulati ng porphyrins a nd others iro n , is not kn o wn. Th e large areas withou t iron or flu or escen ce in the liv er biopsies of our P CT patien t s were ass umed to be normal liver cells. It is perhaps reasonab le to suggest t hat certain cells ini tiate acc umula ti on of iron or porphyrin , a nd those area" will t he n preferenti ally accumulate a n excess of eit her porphyrins or iron . 1t seems reasona ble to conclude t hat in p eT there is an underl ying metaboli c defect , p erh ap s genetica lly determined , whi ch requires the participation of cert ain acquired factor s to resul t in excessive hepatic porphyrin synt hesis. One of t hose acquired , extrin sic factors is iron. The excessive a mount of iron may not be merely a consequen ce of hep atocellular dam age, but may co nt ribut e t c t he evo lutio n of t he lesion (2).
Acknowledgement Th e a utho rs kindly acknowl edge D r . C. J. \VATSON for hi s encoura gem ent, a dv ice and stimulating discus sions throughout this wor k , an d for h elpful cooperation on t h e part of Drs. G. GULMEN and D . B ROW N.
Literature 1. AZIZ, lV1. A., a n d W ATSON, C. J ., An an al y sis of the p orphyrin s of nor m al find cir rh ot ic hum a n liver an d normal b ile . Cli n . Ch im . Acta 26 , 525 -5:l1 (1969). 2. B IE)!PICA, L . K OSOWER, K. , lVIA, :'If. H ., and GCLDFISHER, S., H epati c porph yr ias. Cy toch emical and ultrast ru ctural st ud ies of li ve r in Al P a nd P CT . Arch . P athol , 98, 336- 343 (19 74). 3 . ])E llLIN, 0., E NERBXCK, L., a n d Lrrx n vall , 0. , P crphy ri a eut anea t arda - A genet.ic di sease. A cta. m od, Sca n d . 194 , 265 - 270 (19 73). 4. Do s s , 1\1. (ed ), R egul a t ion of porphyr in a nd h eme bi osynthesi s. P r oceed lnt Con f on R egulat ion of P or phyrin a n d H em e B iosy nth esi s , l\Iarburg a . d . L ahn \ 973 , Ba sel , K a rger S, 1974. 5. - Por phyr in s in hum an d iseases . Proceed. Tn t. P orphyrin Meet ir.g , F rciburg, lVlay 1975, Ba sel , K arger S, 197 6.
176
Z. J. PE'I'RYKA, N. D. KOS'I'ICH and G. J. DHAR, Iron and porphyr in in the liver
6. FELSHER, B. F., JONES, M. L., and REDEKER, A. G., Iron and hepatic uroporphyrin synthesis. Relation in PCT. JAMA 226,663-665 (1973). 7. GROTE, W., SCHMOLDT, A., and BENTHE, H. F., Hepatic porphyrin synthesis in rats after pretreatment with polychlorinated biphenyls (PCB's). Acta pharrnacol. et Toxicol. 36, 215-224 (1975). 8. HABERMAN, H. F., ROSENBERG, F., and MENON, r. A., Porphyria cutanea tarda: Comparison of Cases precipitated by alcohol and estrogens. Canad. Med, Assoc. J. 113, 653-655 (1975). 9. IpPEN, M., und AUST, D., Klinisch-experimentelle Untersuchungen zur Entstehung der Porphyrien. I. Allgemeine und tierexperimontelle Modollversuche. Arch. Derm, Forsch. 245, 110-124 (1972). 10. JACKSON, A. H., SANCOVICH, H. A., FERRAMOLA, A. M., EVANS, x., GAMES, D. E., ;\fATLIX, S. A., ELDER, G. H., and SMITH, S. G., Macrocyclic intermediates in the biosynthesis of porphyrins. Phil. Trans. R. Soc. London B 273,191-206 (1976). 11. JOUBERT, S. M., TALJAARD, J. J. F., and SHANLEY, B. C., Aetiologicalrelationship between hepatic siderosis and symptomatic PCT. Enzyme 16, 305-313 (1973). 12. KUSHNER, J. P., STEINMULLER, D. P., and LEE, G. R., The role of iron in the pathogenesis of porphyria outanea tarda. II. Inhibition of uroporphyrinogen decarboxylase. J. Clin. Invest. 56, 661-667 (1975). 13. LUNDVALL, 0., The effect of phlebotomy therapy in PCT: Its relation to the phlebotomy-induced roduction of iron storage. Acta mod. Scand. 189, 33-49 (1971). 14. MALINA, L., and CHLUMSKY, J., Oestrogen-induced familial porphyria cutanea tarda. Brit. J. Dormatol. 92, 707-709 (1975). 15. MENDOZA, C. E., GRANT, D. L., and SHIELDS, J. B., Body burden of hexaohlorobonzeno in suckling rats and its effects on various organs and on liver porphyrin accumulation. Environ. Physiol, Hiochem. 5, 460-464 (1975). 16. MOLLENHAUER, H. R., JOHNSON, J. H., YOUXGER, R. L., and CLAHK, D. E., Ultrastructural changes in liver of the rat fed hexaehlorobenzene, Amer. J. Vet. Res. 36, 1777-1781 (1975). 17. REIZENSTEIN, P., HOGLUND, S., LANDEGRAN, J., CARLllIARK, B., and FOHSBEHG, K., Iron metabolism in porphyria cutanea tarda. Acta med. Scand. 198,95-99 (1975). 18. TALJAAHD, J. J. F., SHANLEY, B. C., DEPPE, W. M., and JOUBERT, S. M., Porphyrin metabolism in experimenta.l hepatic siderosis in the rat. II. Combined effect of iron overload and hexaehlorobenzene. Brit. J. Haematol. 23, 513-519 (1972). HI. TIMME, A. H., TALJAARD, J. J. F., SHANLEY, B. C., and JOUBERT, S. M., Symptomatic porphyria. Part II. Hepatic changes with hexachlorobenzene. S. A. Meel. J. 48, 1833-1836 (1974). 20. TSCHUDY, D. P., Porphyrin metabolism and tho porphyrias. In Duncan's Diseases of Metabolism, 7th ed., edited by Bondy PK, Philadelphia, 'WB Saunders Co., 1974. Adress: Dr. Z. J. PETRYKA, Xorthwestern Hospital, 810 E. 27th Street, Minneapolis, MN 55407.
University of Minnesota, Medical Research Unit, Northwestern Hospital, Minneapolis, U.S.A.
Location of iron and porphyrin in the liver in porphyria cutanea tarda By ZBYSLAW J. PETRYKA, NIKOLA D. Kosrron and G. JEELANI DRAR1 ) With 2 figures (Received May 9, 1978)
Summary Porphyrin and iron distributions in the liver biopsies of patients with Porphyria cutanea tarda (peT) were investigated by comparison of eomposite photographs from fluorescence microscope and after iron stain. Three distinct areas are visible: 1. red fluorescent areas with porphyrins; 2. blue areas corresponding to iron; 3. areas with neither iron nor porphyrin. The areas with iron or porphyrin do not overlap, therefore, this experiment indicates lack of direct correlation between iron and porphyrin distribution in liver" of Pf"]' patients.
Introduction The clinical manifestations of Porphyria cutanea tarda (POT) are directly related to excessive production of uroporphyrin in the liver (2, 9, 20). Hypersideremia and hepatic siderosis are found in a high percentage of patients with POT (6, I l , 12, 17), however, the incidence of POT among alcoholics (4, 5, 8) is quite low. In various studies in many countries, this incidence is in the range of 1 to 4% (5), which in itself, suggests a genetic factor (3). In liver biopsies from POT patients, it has often been observed that the liver contains an excess of both iron and porphyrin (6,9, Ll , 12, 17). This suggested a direct correlation between hepatic iron overload and porphyrin overproduction in the hepatocytes (6,9, l l , 12, 17). Also, as is well known, treatment by multiple phlebotomies regularly brings about biochemical and clinical remission regardless of the presence of increased stainable iron in the liver (13). Since analysis of the liver provided evidence for iron and porphyrin excess (6, l I, 12, 17), it has generally been assumed that the iron and porphyrin occur in the same areas in the livcr (Il). No report has been found of simultaneous study of the porphyrin and iron locations (1). This common assumption of the presence of iron and porphyrin in the same hepatocytes (17), or even in closely contiguous liver cells, is not confirmed by microscopic studies. The microscopic studies were reported for rats fed with hexaI) Present address: Medical college of Wisconsin Milwaukee County General Hospital, Gastroenterology Section, Milwaukee, WI 53226.
Iron and porphyrin in the liver
169
chlorobenzene and iron (18, 19); hexachlorobenzene induced porphyria in rats serves, at least in some respects, as a model for POT (7, 9,10, 15, 16, 18, 19). The authors (18, 19) have found the porphyrins in the hepatocytes without iron, or where stored iron was depleted to such an extent as not to exhibit iron by staining. This finding represents a discrepancy in respect to the accepted assumption of porphyrins and iron in the liver. In cases of POT precipitated by estrogen (8, 14) without iron in the liver (2, 8), increased porphyrin production was obviously not related to stainable hepatic iron.
Materials and Methods In the present study, tho loc ations of iron and porphyrin wore determined in liver biopsies of four patients having PCT. The informed written consents were obtaino.I from all the patients after the nature of the procedure had been fully explained to them. PCT was diagnosed by the characteristic symptoms and clinical findings supported by the presence of 8- and 7-COOH porphyrins in urine and feces, and prominence of isocoproporphyrin in feces. Th3 latter group of porphyrins is highly characteristic of PCT. Liver biopsies were done with a Menghini neo.lle (0.4 mm bore). The specimens were instantly frozen on dry ice and 5 flm thick frozen sections were prepared. In patient # I, in which the biopsy was kept for two hours at room te.nperature, a diffusion of fluorescence was observed. The usually well clelinoated, intense fluorescence became diffuse. In another patient, # 2, absolute ethanol fixed sections were also prepared; they were compared microscopically with frozen sections. The unstained specimens were observed by visual microscopy and in a Reichert fluorescence microscope with 400 nm exciting light. The location of fluorescence was recorded prior to the iron staining. Color slides and white prints of tho red fluorescence were prepared. For tho former, a Kodak G15 filter was used, and for black and white, two filters, Kodak G 15 and G25. With this combination, the red fluorescence is photographed as white. Thc whole specimen, often 6 to 7 mm long and 1 to 2 mm wide, was photographed piece by piece, resulting in 20 to 30 fragmentary photographs for each biopsy. These, when place side by side, reproduced the general morphology of the section and the locations of red fluorescing areas. After photographing the fluorescence, the same sections (fragments) were stained for iron (standard iron stain). After iron staining, the red fluorescence disappears. Iron stained slides were photographed with the same m'3,:;nification, fragment by fragment, using a Kodak Gl5 filter. The prints placed side by side reproduce the general topography of the specimens, and they were compared with the same areas showing red Fluorescence. The various locations of porphyrin (red fluorescence) were compared with that of iron (blue spots after iron stain). Representative areas of the photographs art! shown in Figs. 1 and 2.
Results and Discussion Examination of liver specimens from peT patients permitted us to conclude that iron and the red fluorescence of porphyrin were located in different areas. Fluorescence in the frozen sections (Fig. 1A) was more diffuse, broader, and not as intense as in absolute ethanol fixed sections (Fig. 2A). In all specimens investigated by us, there were definite areas of red fluorescence. Red flucrescence, related to porphyrins, has a tendency to concentrate in selected areas in the liver. Therefore, the liver section in the fluorescence microscope looks "patchy" with red fluorescence in certain sections and large areas without red fluorescence. A patchy distribution is also observed for iron, the concentration and distribution of iron granules is uneven through the 12
Acta histochem. Bd, 63
170
Z. J.
PETRYKA,
N. D.
KOSTleR
and G. J .
DIIAR
Fig. 1. Li ver biopsy from p el' pati en t s - frozen sect ion s : A and B
=
:j:I: 1 ; A land B!
= :\:I: 2;
A. In fluorescence mi eroscopo (details d escribed in " Meth od s"), the whi te areas correspond to red fluorescen ce of porphyrin ; they a re indicated b y arrows a nd letter " P" . B . In t ra ns mit ted light in mi croscop e aft er iron stain, the black sp ots co rres p on d to stainable iron, indica t ed by arrows and letters "Fe " .
Iron and porph yr in in the li ver
12'
171
172
Z. .J.
P E T H': K.\ ,
X. D .
I~ (J S Tl cH anti
G. J .
)) HA R
I r o n a nd pnr ph y rin in th o liv er
173
A
F ig . 2. Li ver biopsy sec t ion fr om p e T p atient ( # 2) - fixed with absolut e e th a nol. A . I II flu or escence mi cr oscop e, th e wh it e a reas corresp on d t o red f'l uorescen ce of porphyrins ; they a re indi cated b y arrows and let ter " P " . B . I n t ransmitt ed light in m icroscop e after iron st a in , the bl a ck spots corresp on d to stainable iron in d ica ted b y a rrows and letters " F e".
liv er . No differences are observed in frozen vs ethanol fix ed sect ions. There are parts of the liver where a large con centration of iron is noted and ot her areas where there is no ir on , or very little. This ca n be seen in iron stain of fr ozen sections (Fig. IB) and absolute etha nol fix ed sect ions (Fi g. 2B). The irregularities of fl uoresce nce already mentioned are also observed with iron staining . Th e ph otographs of red fluorescence of liver specimens wer e compared with ph otographs of iron stain from the sam e secti on s. A comparison of t he location s of iron in relati on to loca ti on s of porphyrin, was possibl e (Figs. 1 and 2). J n frozen and et hano l fix ed sect ions, large areas of liv er do not contain eit her fluorescence or ir on. Iron is found in th e ar eas where red fluorescen ce is minor or lacking, a nd vice versa . Ther efor e, sections fro m t he liver biopsies
174
Z. J.
PE'I'RYKA,
N.
D.
Kosrrcrr and G. J.
DHAR
Ir on and p orph yrin in th e liver
175
can be subdivided into three maj or areas, one where porphyrin was located (marked with " P" in li'igs. 1 a nd 2), a no t her sect ion where iron was located (marked with " Fe" in Figs. I a nd 2), and a reas with neither iron nor fluorescen ce in significant amount. This subdivision ha s also bee n ob ser ved in rats fed R CB (18, 19). Again, in et ha nol fixed sect ions , red flu or escen ce is bette r defined and areas with porphyrins were more concentrated. Th e diffusion of red flu orescen ce into slight ly pink areas , with ordinary fi xation , was not ob served . The cells a nd location of porphyrin within the cells is clearly visible. The et ha nol fix ation did not affe ct iro n sta ining, which remained ex ac t ly the sa me as in the frozen section (Fi gs. IB and 2B) . Iron loca tions in both froz en a nd etha nol fix ed sections were t he sa me. Th e relative location of iron and porphyrin ca n be seen in Figs. 1 a nd 2 where porphyrins ar e indicat ed by letter " P", iron by letter s " F e" . The ba sis of the differing location of porphyrin and ir on is not clear. It could be theoriz ed that iron located in the liver affects the enzymes t o in crease heme formation, and through negative feedba ck , red uces further porphyrin format ion . If this were true, t he a mount of porphyrin which would be seen migh t be small or negligible. In t he ar eas with cells loaded with porph yrin there would be, if not a defici ency of iron, at least norm al level of iron and th e porphyrins would presumabl y not accumulate there. R ow the division comes a bout betw een cells accumulati ng porphyrins a nd others iro n , is not kn o wn. Th e large areas withou t iron or flu or escen ce in the liv er biopsies of our P CT patien t s were ass umed to be normal liver cells. It is perhaps reasonab le to suggest t hat certain cells ini tiate acc umula ti on of iron or porphyrin , a nd those area" will t he n preferenti ally accumulate a n excess of eit her porphyrins or iron . 1t seems reasona ble to conclude t hat in p eT there is an underl ying metaboli c defect , p erh ap s genetica lly determined , whi ch requires the participation of cert ain acquired factor s to resul t in excessive hepatic porphyrin synt hesis. One of t hose acquired , extrin sic factors is iron. The excessive a mount of iron may not be merely a consequen ce of hep atocellular dam age, but may co nt ribut e t c t he evo lutio n of t he lesion (2).
Acknowledgement Th e a utho rs kindly acknowl edge D r . C. J. \VATSON for hi s encoura gem ent, a dv ice and stimulating discus sions throughout this wor k , an d for h elpful cooperation on t h e part of Drs. G. GULMEN and D . B ROW N.
Literature 1. AZIZ, lV1. A., a n d W ATSON, C. J ., An an al y sis of the p orphyrin s of nor m al find cir rh ot ic hum a n liver an d normal b ile . Cli n . Ch im . Acta 26 , 525 -5:l1 (1969). 2. B IE)!PICA, L . K OSOWER, K. , lVIA, :'If. H ., and GCLDFISHER, S., H epati c porph yr ias. Cy toch emical and ultrast ru ctural st ud ies of li ve r in Al P a nd P CT . Arch . P athol , 98, 336- 343 (19 74). 3 . ])E llLIN, 0., E NERBXCK, L., a n d Lrrx n vall , 0. , P crphy ri a eut anea t arda - A genet.ic di sease. A cta. m od, Sca n d . 194 , 265 - 270 (19 73). 4. Do s s , 1\1. (ed ), R egul a t ion of porphyr in a nd h eme bi osynthesi s. P r oceed lnt Con f on R egulat ion of P or phyrin a n d H em e B iosy nth esi s , l\Iarburg a . d . L ahn \ 973 , Ba sel , K a rger S, 1974. 5. - Por phyr in s in hum an d iseases . Proceed. Tn t. P orphyrin Meet ir.g , F rciburg, lVlay 1975, Ba sel , K arger S, 197 6.
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Z. J. PE'I'RYKA, N. D. KOS'I'ICH and G. J. DHAR, Iron and porphyr in in the liver
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