Editing Active transport (section)

=== Symporter ===

A [[symporter]] uses the downhill movement of one [[Solution (chemistry)|solute species]] from high to low concentration to move another molecule uphill from low concentration to high concentration (against its [[concentration gradient]]). Both molecules are transported in the same direction.

An example is the glucose symporter [[Sodium-glucose transport proteins|SGLT1]], which co-transports one [[glucose]] (or [[galactose]]) molecule into the cell for every two sodium ions it imports into the cell.<ref>{{cite journal|last1=Wright|first1=EM|last2=Loo|first2=DD|last3=Panayotova-Heiermann|first3=M|last4=Lostao|first4=MP|last5=Hirayama|first5=BH|last6=Mackenzie|first6=B|last7=Boorer|first7=K|last8=Zampighi|first8=G|title='Active' sugar transport in eukaryotes.|journal=The Journal of Experimental Biology|date=November 1994|volume=196|pages=197–212|doi=10.1242/jeb.196.1.197|pmid=7823022}}</ref> This [[symporter]] is located in the small intestines,<ref>{{cite journal|last1=Dyer|first1=J|last2=Hosie|first2=KB|last3=Shirazi-Beechey|first3=SP|title=Nutrient regulation of human intestinal sugar transporter (SGLT2) expression.|journal=Gut|date=July 1997|volume=41|issue=1|pages=56–9|pmid=9274472|doi=10.1136/gut.41.1.56|pmc=1027228}}</ref> heart,<ref>{{cite journal|last1=Zhou|first1=L|last2=Cryan|first2=EV|last3=D'Andrea|first3=MR|last4=Belkowski|first4=S|last5=Conway|first5=BR|last6=Demarest|first6=KT|title=Human cardiomyocytes express high level of Na+/glucose cotransporter 1 (SGLT2).|journal=Journal of Cellular Biochemistry|date=1 October 2003|volume=90|issue=2|pages=339–46|pmid=14505350|doi=10.1002/jcb.10631|s2cid=21908010}}</ref> and brain.<ref>{{cite journal|last1=Poppe|first1=R|last2=Karbach|first2=U|last3=Gambaryan|first3=S|last4=Wiesinger|first4=H|last5=Lutzenburg|first5=M|last6=Kraemer|first6=M|last7=Witte|first7=OW|last8=Koepsell|first8=H|title=Expression of the Na+-D-glucose cotransporter SGLT1 in neurons.|journal=Journal of Neurochemistry|date=July 1997|volume=69|issue=1|pages=84–94|pmid=9202297|doi=10.1046/j.1471-4159.1997.69010084.x|s2cid=34558770|doi-access=free}}</ref> It is also located in the S3 segment of the [[proximal tubule]] in each [[nephron]] in the [[kidney]]s.<ref>{{cite journal|author =Wright EM|year=2001|title=Renal Na<sup>+</sup>-glucose cotransporters|journal=Am J Physiol Renal Physiol|pmid=11133510|volume=280|issue=1|pages=F10–8|doi=10.1152/ajprenal.2001.280.1.F10}}</ref>  Its mechanism is exploited in [[Oral rehydration therapy|glucose rehydration therapy]]<ref name="pmid8917597">{{cite journal|last1=Loo|first1=DD|last2=Zeuthen|first2=T|last3=Chandy|first3=G|last4=Wright|first4=EM|title=Cotransport of water by the Na+/glucose cotransporter.|journal=Proceedings of the National Academy of Sciences of the United States of America|date=12 November 1996|volume=93|issue=23|pages=13367–70|pmid=8917597|doi=10.1073/pnas.93.23.13367|pmc=24099|bibcode=1996PNAS...9313367L|doi-access=free}}</ref> This mechanism uses the absorption of sugar through the walls of the intestine to pull water in along with it.<ref name="pmid8917597" /> Defects in SGLT2 prevent effective reabsorption of glucose, causing [[Glucosuria|familial renal glucosuria]].<ref>{{cite journal|vauthors=Wright EM, Hirayama BA, Loo DF |year=2007|title=Active sugar transport in health and disease|pmid=17222166|volume=261|issue=1|pages=32–43|doi=10.1111/j.1365-2796.2006.01746.x|journal=Journal of Internal Medicine|doi-access=}}</ref>