title: Glucagon stimulates chloride transport independently of cyclic AMP in the rat medullary TAL.
abstract: The effect of glucagon on chloride transport was studied in the rat medullary thick ascending limb (MTAL) perfused in vitro. In the bath, 10(-6) M glucagon increased the efflux coefficient of Cl (KeCl) from 6.88 +/- 0.21 x 10(5) to 9.65 +/- 0.38 x 10(-5) cm.sec -1 (P less than 0.01) without changing the influx coefficient (KiCl; 2.87 +/- 0.54 x 10(-5) in control vs. 2.83 +/- 0.57 x 10(-5) cm.sec-1 with glucagon) or transepithelial potential difference (4.8 +/- 0.76 in control vs. 5.0 +/- 0.71 mV with glucagon). A physiological concentration of glucagon (10(-8), (10(-10) M) also increased chloride efflux significantly. Pretreatment of tubules with luminal furosemide (10(-5) M) and/or basolateral ouabain (10(-4) M) completely abolished the effect of glucagon. In isolated MTALs incubated in the same medium as that used in the microperfusion study, 10(-6) M glucagon stimulated cAMP production by 255.2 +/- 33.7% (P less than 0.01). However, neither dibutyryl cAMP (10(-3), 10(-4) M) nor forskolin (10(-4), 10(-6) M) increased the chloride efflux. It is concluded that: 1) Glucagon stimulates net Cl reabsorption by increasing Cl efflux in the rat MTAL; and 2) cyclic AMP is not responsible for this effect of glucagon.
authors: Department of Medicine, Jichi Medical School, Tochigi, Japan.
authors: Y
authors: Y
authors: Ando
authors: K
authors: K
authors: Tabei
authors: H
authors: H
authors: Furuya
authors: Y
authors: Y
authors: Asano
mesh_terms: D000818:Animals; D001692:Biological Transport; D002712:Chlorides / Q000378:metabolism*; D000242:Cyclic AMP / Q000502:physiology*; D005665:Furosemide / Q000494:pharmacology; D005934:Glucagon / Q000494:pharmacology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism*; D008138:Loop of Henle / Q000378:metabolism*; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D002712:Chlorides; D007473:Ion Channels; D010042:Ouabain; D005665:Furosemide; D005934:Glucagon; D000242:Cyclic AMP