| Project/Area Number |
60480107
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
General physiology
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| Research Institution | University of Tokyo |
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Principal Investigator |
HOSHI Takeshi Faculty of Medicine, University of Tokyo (Professor), 医学部, 教授 (60004537)
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| Co-Investigator(Kenkyū-buntansha) |
MARUYAMA Yoshio Faculty of Medicine, University of Tokyo (Instructor), 医学部, 助手 (00133942)
MATSUNAGA Hiroshi Faculty of Medicine, University of Tokyo (Instructor), 医学部分院, 助手 (50165841)
TAKUWA Noriko Faculty of Medicine, University of Tokyo (Instructor), 医学部, 助手 (70150290)
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| Project Period (FY) |
1985 – 1986
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥6,300,000 (Direct Cost: ¥6,300,000)
Fiscal Year 1986: ¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1985: ¥4,000,000 (Direct Cost: ¥4,000,000)
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| Keywords | Proton-peptide cotransport / transport stoichiometry / specificity / peptide-transport potential / microclimate pH / intracellular pH / brush border membrane / intestine / 腎臓 |
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| Research Abstract |
Di- and tripeptide-induced changes in transmural potential were independent of <Na^+> , dependent on both extra- and intracellular pH and conformed to Michaelis-Menten kinetics. In contrast, amino-acid transport potentials were absolutely dependent on the presence of <Na^+> . Accordingly, recording of the peptide transport potential in the absence of <Na^+> enabled us to explore the specificity, multiplicity of the peptide carrier. The results of the recording for more than 20 peptides revealed that glycyl-and alanyl-dipeptides were transported by a common carrier. Some of tripeptides, triglycine and trialanine were also found to be transported by the same carrier. The values of <K_t> for these peptides fell in a relatively narrow range (0.5-2.0 mM), indicating the peptide carrier transfers various amino acids together without discrimination according to chemical structure.
To clarify the characteristics of the peptide transport system in intestinal and renal brush border membranes, upt
… More
ake of dipeptide (Gly-Gly) was examined under various medium conditions. It was found that the uptake of Gly-Gly was independent of <Na^+> , stimulated by an imposed pH gradient and electrogenic. A marked overshoot uptake was demonstrated in the presence of a pH and transmembrane voltage gradients. The data suggested that dipeptides are cotransported with <H^+> . Simultaneous measurements of peptide-induced increase in short-circuit current and peptide influx across everted intestines under <Na^+> -free conditions revealed that <H^+> /Gly-Gly cotransport had a stoichiometry of 2:1. Theoretical analysis of relationship between cotransport-induced membrane current across the luminal membrane and cotransport-induced increase in short-circuit current across epithelial layer supported the estimated stoichiometry.
Measurements of intracellular pH and the microclimate pH in the vicinity of the surface of the intestinal epithelial cells indicated that a pH gradient of about one pH unit (higher inside the cell) existed across the brush border membrane. The stoichiometry of 2:1 and the presence of a pH gradient support the idea that the peptide transport system is capable of establishing a much higher concentration gradient of peptides as compared to <Na^+> -dependent sugar or amino acid transport system. Less
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