Sites of Formation of the Serum Proteins Transferrin and Hemopexin

Thorbecke, G. J.; Liem, H. H.; Knight, Simon A. B.; Cox, K.; Müller‐Eberhard, Ursula

doi:10.1172/jci107234

Cited by 63 publications

(18 citation statements)

References 20 publications

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“…Mammalian hemopexins are not only synthesized in the hepatic parenchymal cells (Thorbecke et al, 1973), but also in other cell types including neurons of the peripheral nervous system, retinal photoreceptor and ganglion cells, and ovary as minor sites of synthesis (Swerts et al, 1992;Hunt et al, 1996;Chen et al, 1998). Transcripts of goldfish Wap65 have been reported to be present in hepatopancreas, ovary, eye, gill and muscle (Kikuchi et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

The occurrence of two types of hemopexin-like protein in medaka and differences in their affinity to heme

Hirayama

Kobiyama

Kinoshita

et al. 2004

Journal of Experimental Biology

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Full-length cDNA clones encoding two types of hemopexin-like protein, mWap65-1 and mWap65-2, were isolated from the HNI inbred line of medaka Oryzias latipes. The deduced amino acid sequence of mWap65-2 resembled mammalian hemopexins more closely than that of mWap65-1. Histidine residues required for the high affinity of hemopexins for hemes were conserved in mWap65-2, but not in mWap65-1. Surprisingly, mWap65-1, but not mWap65-2, showed heme-binding ability as revealed by hemin-agarose affinity chromatography, even though mWap65-1 lacked the essential histidine residues. Furthermore, RT-PCR analysis of different tissues demonstrated that the transcripts of mWap65-2 were restricted to liver, whereas those of mWap65-1 were found in various tissues including liver, eye, heart and brain. Quantitative RT-PCR revealed that transcripts of mWap65-2 were expressed earlier than those of mWap65-1 during ontogeny. However, the accumulated mRNA levels of both mWap65-1 and mWap65-2 did not differ significantly in fish acclimated to either 10°C or 30°C for 5 weeks. These characteristics suggest that the two proteins have different physiological functions and that mWap65-2 is not a hemopexin.

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Section: Discussionmentioning

confidence: 99%

The occurrence of two types of hemopexin-like protein in medaka and differences in their affinity to heme

Hirayama

Kobiyama

Kinoshita

et al. 2004

Journal of Experimental Biology

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“…A combination of retinol, testosterone, insulin, and follicle-stimulating hormone (FSH) regulates testicular transferrin (11). In addition, transferrin synthesis has been reported in brain, bone marrow, spleen, and submaxillary gland (5,8,12). No regulatory factors have been identified for transferrin synthesis in these tissues.…”

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confidence: 99%

Rat transferrin gene expression: tissue-specific regulation by iron deficiency.

Idzerda

Huebers

Finch

et al. 1986

Proc. Natl. Acad. Sci. U.S.A.

180

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“…The fetal serum concentrations do not reflect the relative amounts of synthesis of these proteins by the liver observed in our in vitro data. Alternate sites of synthesis may be the reason for the substantial serum transferrin levels (17). The very low serum hemopexin levels encountered imply either a low rate of incorporation of radiolabeled amino acids into hemopexin or rapid catabolism.…”

Section: Discussionmentioning

confidence: 99%

“…Hemopexin has a higher binding affinity for metalloporphyrins than albumin (15) and is instrumental in the disposal of heme (5,8,9,14,19). The liver is the site of hemopexin synthesis in rhesus monkeys (17), rabbits (17), and rats (12). In the present study, human fetal tissues were cultured and examined for the relative amounts of hemopexin, albumin, and transferrin produced.…”

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confidence: 97%

Hemopexin Synthesis in Vitro by Human Fetal Tissues

et al. 1975

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ExtractSerum concentrations of hemopexin, transferrin, and albumin were measured for 12 fetuses between 14 and 36 weeks of gestational age. Hemopexin levels ranged from 7 to 64 pg/ml, transferrin levels ranged from 280 to 928 pg/ml, and albumin levels ranged from 13 to 59 mg/ml. In general, the serum concentrations of these three proteins increased with advancing gestation.Placenta, thymus, and colon did not incorporate 14C-labeled amino acids into hemopexin, transferrin, or albumin. By contrast, radioimmune precipitates for five culture supernatants of liver indicated significant synthesis of albumin and hemopexin.[MC]Albumin accounted for 22-73% and [14C]hemopexin 1.1-4.2% of the total 14C-labeled proteins. In each instance, the ["Cltransferrin was below 1% of the total l 4 C-labeled proteins. SpeculationThese data show considerable synthesis of albumin and hemopexin, but not transferrin, by the liver during fetal life. That hemopexin levels are lower in fetal than adult sera may reflect an increased requirement for heme disposal. Possibly, the increased turnover of hemopexin is related to the shortened lifespan of fetal in comparison with adult erythrocytes.Mammalian serum contains two major porphyrin-binding proteins, hemopexin and albumin (1 I). Hemopexin has a higher binding affinity for metalloporphyrins than albumin (15) and is instrumental in the disposal of heme (5,8,9,14,19). The liver is the site of hemopexin synthesis in rhesus monkeys (17), rabbits (17), and rats (12). In the present study, human fetal tissues were cultured and examined for the relative amounts of hemopexin, albumin, and transferrin produced. MATERIALS A N D METHODS FETAL TISSUESSerum samples of fetuses were obtained by heart puncture.Tissuc culturcs of livcr, placenta, thymus, a n d colon of h u m a n fetuses, 12-25 weeks old, were developed by Dr. Peter F. Kohler (20), employing [14C]lysine and [14C]isoleucine (4). Culture supernatants were dialyzed against 0.015 M phosphate-buffered saline (PBS), pH 7.4, lyophilized, dissolved in distilled water (0.2-0.3 ml), shipped to La Jolla on Dry Ice, and stored at 7 0°.Tissues for absorption of antisera were obtained from fetuses within 5 hr of saline-induced abortion. Small pieces of liver, placenta, thymus, and colon were passed through a stainless steel mesh with the aid of screen rakes. Cells were washed three times with PBS and mixed with 3 volumes antiserum/l volume of cells. The mixtures were incubated at 37O for 30 min, at 4' for 48 hr, and then the cells were removed by centrifugation at 1,200 x g for 30 min. T o 5-50-pl aliquots of culture supernatant, 50 1 1 normal human serum as carrier protein were added and the nonspecific radioactivity was precipitated by addition of equivalent amounts of R G G and anti-BGG. T h e mixture was incubated 37' for 30 min, at 4' overnight, and centrifuged at 1,200 x g for 30 min at 4'. The supernatants were then used for precipitation with the monospecific antisera added to antibody excess. The reaction mixtures were incubated and centrifuged as...

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Sites of Formation of the Serum Proteins Transferrin and Hemopexin

Cited by 63 publications

References 20 publications

The occurrence of two types of hemopexin-like protein in medaka and differences in their affinity to heme

The occurrence of two types of hemopexin-like protein in medaka and differences in their affinity to heme

Rat transferrin gene expression: tissue-specific regulation by iron deficiency.

Hemopexin Synthesis in Vitro by Human Fetal Tissues

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