Investigations on the role of hemopexin and albumin in plasma clearance and tissue distribution of Sn-protoporphyrin.
The mechanism of the clearance of circulating tin-protoporphyrin (Sn-PP), a competitive inhibitor of heme oxygenase in the degradation of heme to bilirubin, is unknown. Two serum proteins, albumin and hemopexin, which are instrumental in the delivery of iron-protoporphyrin (heme) to the liver, also bind metalloporphyrins with high affinity and may aid in targeting their tissue distribution. After intravenous injection of 1 mumol Sn-PP/kg, the serum concentration of hemopexin decreased in human subjects, rats, and rabbits within 24 hours to a similar extent (30% to 50%). This finding suggested that hemopexin may have a role in the tissue distribution of Sn-PP. However, when rats were injected with Sn-PP in saline solution or complexed with albumin, more Sn-PP was taken up by the liver and testes than when Sn-PP was complexed with hemopexin. These results indicate that hemopexin does not preferentially target Sn-PP to the liver and may not be the preferred vehicle for clearance of circulating Sn-PP.
Simionatto
C S
CS
Rockefeller University Hospital, New York.
Drummond
G S
GS
Landaw
S A
SA
Kappas
A
A
Liem
H
H
Vincent
S
S
Muller-Eberhard
U
U
D000418:Albumins / Q000378:metabolism*; D000818:Animals; D006466:Hemopexin / Q000378:metabolism*; D006801:Humans; D008297:Male; D008665:Metalloporphyrins / Q000097:blood / Q000378:metabolism*; D011485:Protein Binding; D011524:Protoporphyrins / Q000097:blood / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014018:Tissue Distribution
D000418:Albumins; D008665:Metalloporphyrins; D011524:Protoporphyrins; D006466:Hemopexin; C032628:tin protoporphyrin IX