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No involvement of system N, system y + and the oligopeptide‐H + transport system in the uptake of methylmercury in rat erythrocytes
Author(s) -
Wu Guang
Publication year - 1998
Publication title -
journal of applied toxicology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.784
H-Index - 87
eISSN - 1099-1263
pISSN - 0260-437X
DOI - 10.1002/(sici)1099-1263(199801/02)18:1<55::aid-jat478>3.0.co;2-l
Subject(s) - oligopeptide , methylmercury , chemistry , transport system , biochemistry , environmental chemistry , bioaccumulation , peptide , transport engineering , engineering
Previous studies have investigated a number of possible transport systems for the uptake of methylmercury (MeHg) in erythrocytes. In the present study, three additional systems were studied. The uptake of MeHg by isolated erythrocytes from rats was studied at 5°C and 20°C. Glutamine was used to test system N and system y + , and glycylglycine was used to test the oligopeptide‐H + transport system. The Hill equation was used in kinetic analysis. The results show that both glutamine and glycylglycine stimulated the uptake of MeHg, but the stimulation by glycylglycine is stronger than by glutamine, and the stimulation at 5°C is stronger than at 20°C (mean values are 167.98% and 83.68% in the glycylglycine group at 5°C and 20°C versus 26.28% and 19.23% in the glutamine group at 5°C and 20°C). The kinetic analysis shows that: the Michaelis‐Menten constant K m increased as temperature increased in both groups and was larger in experimental groups than in control groups; the Hill constants increased as temperature increased in both groups and were smaller in experimental groups than in control groups; and as temperature increased, maximum velocity V max increased in control groups and decreased in experimental groups, and was larger in experimental groups than in control groups, with the exception of the glycylglycine group at 20°C. The results demonstrated that system N, system y + and oligopeptide‐H + transport systems were not involved in the in vitro uptake of MeHg into erythrocytes. The stimulation by glutamine and glycylglycine might be related to some signalling pathways, through which nitric oxide and oligopeptide serve as messengers and cause functional alterations in the uptake of MeHg. © 1998 John Wiley & Sons, Ltd.