Transport of galactose and sodium across lizard duodenum

Gómez, Tomás; Badía, P.; Bolaños, A.; Lorenzo, A.

doi:10.1016/0300-9629(86)90469-x

Cited by 5 publications

(6 citation statements)

References 21 publications

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“…The tissues were maintained for 20-40 min under opencircuit conditions and then short circuited. As has been reported several times for this same preparation (8,12), no differences were observed between the transmural PD, I sc , and G t between stable open-circuit and short-circuit measurements. As can be seen in Fig.…”

Section: Resultssupporting

confidence: 82%

“…Recently, we observed the presence of an active absorption of L-alanine transport in the upper small intestine of the lizard Gallotia galloti. The intestinal physiology of this animal model has been studied in our laboratory over the last two decades, and many of the intestinal transport systems at different intestinal segments have been characterized (2,3,8,12).…”

mentioning

confidence: 99%

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Membrane mechanisms for electrogenic Na⁺-independentl-alanine transport in the lizard duodenal mucosa

Dı́az

Medina

Gómez

et al. 2000

American Journal of Physiology-Regulatory, Integrative and Comp

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The active Na(+)-independent transport of L-alanine across the duodenal mucosa of the lizard Gallotia galloti was studied in Ussing-type chambers using a computer-controlled voltage clamp. Addition of L-alanine to the Na(+)-free bathing solutions resulted in a significant L-alanine absorption (J(net)) that was paralleled by an increase in transepithelial short-circuit current (I(sc)) and potential difference (PD) without apparent changes in the tissue conductance. The concentration dependence of J(net), PD, and I(sc) displayed Michaelis-Menten kinetics. L-alanine-induced electrical changes were completely inhibited by external alkaline pH or by the H(+)-ionophore carbonyl cyanide m-chlorophenyl-hydrazone in the bathing solution. The alanine-induced electrogenicity was dependent on the presence of extracellular K(+) and could be blocked by serosal Ba(2+) or mucosal orthovanadate. These results suggest the existence of an H(+)-coupled L-alanine cotransport at the apical membrane of enterocytes. The favorable H(+) driving force is likely to be maintained by an apical vanadate-sensitive H(+)-K(+)-ATPase, allowing the extrusion of H(+) in an exchange with K(+). Potassium exit through a basolateral barium-sensitive conductance provides the key step for the electrogenicity of L-alanine absorption.

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Section: Resultssupporting

confidence: 82%

mentioning

confidence: 99%

Membrane mechanisms for electrogenic Na⁺-independentl-alanine transport in the lizard duodenal mucosa

Dı́az

Medina

Gómez

et al. 2000

American Journal of Physiology-Regulatory, Integrative and Comp

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“…The tissues were maintained for 20-40·min under open-circuit conditions and were then shortcircuited. As has been reported several times for this same preparation (Gómez et al, 1986;Lorenzo et al, 1989b), no differences were observed between the transmural potential difference (PD), short-circuit current (Isc) and tissue conductance (Gt) between stable open-circuit and short-circuit measurements. As can be seen in Table·1, under control conditions, transepithelial PD was approximately 2.0·mV and the mean Isc was 0.77·µequiv.·cm -2 ·h -1 , the serosal side of the tissue being electrically positive compared with the luminal side, which parallels our previous observations (Gómez et al, 1986;Medina et al, 2001).…”

Section: Effects Of Forskolin Theophylline and Db-camp On Totalsupporting

confidence: 63%

“…As has been reported several times for this same preparation (Gómez et al, 1986;Lorenzo et al, 1989b), no differences were observed between the transmural potential difference (PD), short-circuit current (Isc) and tissue conductance (Gt) between stable open-circuit and short-circuit measurements. As can be seen in Table·1, under control conditions, transepithelial PD was approximately 2.0·mV and the mean Isc was 0.77·µequiv.·cm -2 ·h -1 , the serosal side of the tissue being electrically positive compared with the luminal side, which parallels our previous observations (Gómez et al, 1986;Medina et al, 2001). Both PD and Isc were significantly increased by forskolin, theophylline and db-cAMP, in agreement with most studies performed in different animal models, including lizard intestine (Bridges et al, 1983;Díaz and Lorenzo, 1991;Lorenzo et al, 1989a).…”

Section: Effects Of Forskolin Theophylline and Db-camp On Totalsupporting

confidence: 63%

“…The electrical measurements were made as described previously (Gómez et al, 1986) using calomel (for voltage sensing) and Ag/AgCl electrodes (for current passage) connected to the bathing solutions through 4% (v/w) agar bridges. Electrical measurements were continuously monitored with an automatic computer-controlled voltage-clamp device (AC-microclamp) and hardcopied.…”

Section: Electrical Measurementsmentioning

confidence: 99%

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Regulation of L-alanine transport systems A and ASC by cyclic AMP and calcium in a reptilian duodenal model

Gómez

Medina

Ramírez

et al. 2003

Journal of Experimental Biology

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SUMMARYThe regulation of neutral amino acid transport by cyclic AMP (cAMP) and calcium across the isolated duodenum of the lizard Gallotia gallotihas been studied under short-circuit conditions. Active L-alanine transport was stimulated by forskolin, theophylline and dibutyryl cyclic AMP (db-cAMP). All these agents increased transmural potential difference (PD) and short-circuit current (Isc) in a manner consistent with the activation of a chloride secretory pathway. Both forskolin and theophylline increased intracellular cAMP levels in the lizard duodenal mucosa. Addition of calcium ionophore A23187 rapidly reduced mucosa-to-serosa L-alanine fluxes and diminished net L-alanine transport. Despite the reduction of alanine fluxes by A23187, transepithelial PD and Iscvalues were increased by the ionophore. Analyses of the responses of isolated transport pathways indicated that the Na+-independent L-alanine transport system was unaffected by db-cAMP or calcium ionophore. By contrast,Na+-dependent transport activities were profoundly modified by these agents. Thus, while system A [α-methylamino-isobutiric acid(MeAIB)-transporting pathway] was stimulated by increased calcium, system ASC activity was nearly abolished. Calcium ionophore also potentiated the electrogenic response of system A. Forskolin strongly stimulated system ASC activity but left system A activity unchanged. Activation of system ASC by forskolin was clearly electroneutral, as pre-incubation of the tissues with the chloride channel blocker diphenylamine-2-carboxilic acid (DPC) completely prevented forskolin-induced transepithelial electrical responses. It is concluded that intracellular messengers cAMP and calcium oppositely modulate active Na+-dependent L-alanine transport in the lizard intestine. The different sensitivity exhibited by individual transport pathways may well account for the changes observed in overall alanine transport.

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Toxicological Effects of Inhaled Crude Oil Vapor

Fedan,

Thompson,

Sager

et al. 2024

Curr Envir Health Rpt

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Purpose of Review The purpose of this review is to assess the toxicological consequences of crude oil vapor (COV) exposure in the workplace through evaluation of the most current epidemiologic and laboratory-based studies in the literature. Recent Findings Crude oil is a naturally occuring mixture of hydrocarbon deposits, inorganic and organic chemical compounds. Workers engaged in upstream processes of oil extraction are exposed to a number of risks and hazards, including getting crude oil on their skin or inhaling crude oil vapor. There have been several reports of workers who died as a result of inhalation of high levels of COV released upon opening thief hatches atop oil storage tanks. Although many investigations into the toxicity of specific hydrocarbons following inhalation during downstream oil processing have been conducted, there is a paucity of information on the potential toxicity of COV exposure itself. Summary This review assesses current knowledge of the toxicological consequences of exposures to COV in the workplace.

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Transport of galactose and sodium across lizard duodenum

Cited by 5 publications

References 21 publications

Membrane mechanisms for electrogenic Na⁺-independentl-alanine transport in the lizard duodenal mucosa

Membrane mechanisms for electrogenic Na⁺-independentl-alanine transport in the lizard duodenal mucosa

Regulation of L-alanine transport systems A and ASC by cyclic AMP and calcium in a reptilian duodenal model

Toxicological Effects of Inhaled Crude Oil Vapor

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Transport of galactose and sodium across lizard duodenum

Cited by 5 publications

References 21 publications

Membrane mechanisms for electrogenic Na+-independentl-alanine transport in the lizard duodenal mucosa

Membrane mechanisms for electrogenic Na+-independentl-alanine transport in the lizard duodenal mucosa

Regulation of L-alanine transport systems A and ASC by cyclic AMP and calcium in a reptilian duodenal model

Toxicological Effects of Inhaled Crude Oil Vapor

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Membrane mechanisms for electrogenic Na⁺-independentl-alanine transport in the lizard duodenal mucosa

Membrane mechanisms for electrogenic Na⁺-independentl-alanine transport in the lizard duodenal mucosa