Transport of phosphate across intestinal and renal epithelia is essential for normal phosphate balance, yet we know less about the mechanisms and regulation of intestinal phosphate absorption than we do about phosphate handling by the kidney. Recent studies have provided strong evidence that the sodium-phosphate cotransporter NaPi-IIb is responsible for sodium-dependent phosphate absorption by ...

The present study aimed to investigate the effects of root surface iron plaque on the uptake kinetics of arsenite and arsenate by excised roots of rice (Oryza sativa) seedlings. The results demonstrated that the presence of iron plaque enhanced arsenite and decreased arsenate uptake. Arsenite and arsenate uptake kinetics were adequately fitted by the Michaelis-Menten function in the absence of ...

Folate transport in phenylhydrazine-induced rabbit reticulocytes was studied with the non-metabolized folate-analog, methotrexate. The time-course of methotrexate uptake into a mixed population of reticulocytes and mature erythrocytes is a two-component process consisting of a small, but rapid, initial uptake phase followed by a much slower uptake component which remains essentially constant ov...

The kinetics of human red blood cell Cl transport have been studied under nonequilibrium conditions to determine whether or not an outward Cl gradient can recruit the transport protein from an inward-facing to an outward-facing configuration. Three kinds of evidence are consistent with this outward recruitment. First, the initial net Cl efflux into a Cl-free phosphate medium is independent of t...

Man has a limited capacity to absorb riboflavin (1-3) and thiamin (4, 5). The gastrointestinal absorption of these vitamins is describable by Michaelis-Menten type kinetics, characteristic of saturable, specialized absorption processes (6). Both vitamins are phosphorylated in the intestinal mucosa during absorption (7-9) and there is evidence suggesting that this process is the basic mechanism ...

We examined the effects of amylin on 3- O-methyl-d-glucose (3- O-MG) transport in perfused rat hindlimb muscle under hyperinsulinemic (350 μU/ml, 2,100 pmol/l) conditions. Amylin at 100 nmol/l concentration inhibited 3- O-MG transport relative to control in all three basic muscle fiber types. Transport decreased in slow-twitch oxidative (from 5.65 ± 1.13 to 3.46 ± 0.71 μmol ⋅ g-1 ⋅ h-1), fast-t...

Concentrative uptake of 16 amino acids by membrane vesicles isolated from Staphy2ococcus aureus is stimulated 3 to 100 times by the conversion of L-a-glycerol phosphate to dihydroxyacetone phosphate. With the exception of ascorbate-phenazine methosulfate, n-lactate, phosphoenolpyruvate, ATP, and a number of other metabolites and cofactors do not replace or-glycerol phosphate. Amino acid transpo...