AVAILABLE ONLINE: DOWNLOAD FREE Full Version PC / Mac / Android / iPhone / iPad.Chloroalkyl ureas and amidine derivatives as substrates for the active transport by urea transporters.
The urea transporter (UT) is an ammonium-specific carrier expressed in mammalian kidney and several other tissues. Several chloroalkylureas and amidines were investigated as substrate analogues for UT in Xenopus oocytes. Dose-response curves for [3H]urea transport in oocytes showed that the chloroethylurea derivative is more potent than urea itself. For a panel of alkane ureas, we compared their urea transport with that of 1,1-bis(hydroxymethyl)propargyl urea, an urea transport substrate. Urea transport was significantly decreased by the introduction of a single methylene group, in contrast to the case for the chloroalkylurea derivatives. NMR analysis of the oocytes revealed that the ligand-protein complexes formed with both ligand classes are quite different. Oocytes expressing the UT expressed Vmax values for the chloroethylurea and amidine derivatives of between 0.2 and 0.3 pmol of urea/oocyte/min, and between 0.5 and 0.6 pmol of urea/oocyte/min, respectively. Urea transport by UT in oocytes expressing UT-A or UT-B is stimulated by urea-like guanidines and aminoguanidines. With respect to the uptake of 1,1-bis(hydroxymethyl)propargyl urea, this result is consistent with the presence of an internal aqueous compartment in the UTs of UT-A and UT-B, although it is unclear whether the aqueous compartment is contained within the pore or is located in the cytoplasmic side of the pore. The lack of effects of guanidine derivatives on urea transport by UT-A and UT-B is consistent with the requirement for a water-filled pocket in the central cavity of the transporter for the guanidines.Howard F. Kilgour
Howard Francis Kilgour (born August 16, 1927) is a retired professional football player who played offensive guard for four seasons for the Pittsburgh Steelers.
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Category:1927 births
Category:Living people
Category:Pittsburgh
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