Stereoselective transport of histidine in rat lung microvascular endothelial cells

Abstract

The transport characteristics of L- and D-histidine through the blood-lung barrier were studied in cultured rat lung microvascular endothelial cells (LMECs). L-Histidine uptake was a saturable process. The addition of metabolic inhibitors [2,4-dinitrophenol (DNP) and rotenone] reduced the uptake rate of L-histidine. Ouabain, an inhibitor of Na(+)-K(+)-ATPase, also reduced uptake of L-histidine. Moreover, the initial L-histidine uptake rate was reduced by the substitution of Na(+) with choline chloride and choline bicarbonate in the incubation buffer. The system N substrate, L-glutamic acid gamma-monohydroxamate, also inhibited uptake of L-histidine. However, system N-mediated transport was not pH sensitive. These results demonstrated that L-histidine is actively taken up by a system N transport mechanism into rat LMECs, with energy supplied by Na(+). Moreover, the Na(+)-independent system L substrate, 2-amino-2-norbornanecarboxylic acid (BCH), had an inhibitory effect on L-histidine uptake in Na(+) removal, indicating facilitated diffusion by a Na(+)-independent system L transport into the rat LMECs. These results provide evidence for there being at least two pathways for L-histidine uptake into rat LMECs, a Na(+)-dependent system N and Na(+)-independent system L process. On the other hand, the uptake of D-histidine into rat LMECs was not reduced by the addition of DNP, rotenone, or ouabain, or by Na(+) replacement. Although the uptake of D-histidine was reduced in the presence of BCH, the addition of L-glutamic acid gamma-monohydroxamate did not significantly decrease uptake of D-histidine. These results suggest that the uptake of D-histidine by rat LMECs has different characteristics compared with its isomer, L-histidine, indicating that system N transport did not involve D-histidine uptake.

Prolonged Hypoxia Augments L-Citrulline Transport By System A In The Newborn Piglet Pulmonary Circulation

“…In particular, the L-glutamine influx in porcine PAECs 43 and rat lung microvascular endothelial cells 44 was shown to be predominantly mediated by the Na + -dependent system, ASC. L-Histidine uptake in rat lung microvascular endothelial cells was shown to involve both the Na + -dependent System N and the Na + -independent System L. 8 L-Glutamic acid uptake in bovine PAECs was previously shown to be mostly Na + dependent. 45 Taken together, these studies show that Na + -dependent systems are involved in neutral amino acid transport in PAECs.…”

“…6,7 Remarkably, little is known about the neutral amino acid transporters responsible for L-citrulline transport into PAECs. 8 The Na + -dependent neutral amino acid transporters (SNATs) are one of the major systems responsible for neutral amino acid transport in mammalian cells. 9 -11 SNATs are expressed in most cell types and are categorized as System A or System N, dependent in part on their functional properties.…”

Uptake of L-histidine and histamine biosynthesis at the blood-brain barrier

“…For in vitro studies, rat BMEC were isolated and cultured from rat brains as previously described [1], and subcultured cells were grown on collagen-coated culture flask and slide, and on transwell membrane. Then, L-histidine uptake rate, assay of L-histidine decarboxylase (HDC) activity, immunofluorescence analysis of HDC protein distribution, expression of HDC mRNA by RT-PCR and paracellular transport clearance of fluorescein were performed in rat BMECs [1,2,3]. Values cited in results section are mean AE SEM for n = 5 independent determinations.…”

Enhancing Effect of Zinc on l-Histidine Transport in Rat Lung Microvascular Endothelial Cells

“…Rat LMECs were isolated using a modification of the technique described previously [3,11]. Twenty rats were killed by decapitation.…”

“…uptake into cultured rat lung microvascular endothelial cells (LMECs), a Na + -dependent system-N and an Na + -independent system-L process [3]. L-histidine, an essential amino acid, is a precursor of histamine, which initiates transitory increases in endothelial permeability in situ and in vitro [4,5].…”