ISSN:
1432-2013
Keywords:
Glucagon
;
Transepithelial ion net fluxes
;
Na+, Cl−, K+, Ca2+, Mg2+ transport
;
Electron microprobe
;
Mouse kidney
;
In vitro microperfusion
;
Cortical and medullary thick ascending limb of Henle's loop
;
In vivo micropuncture study
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The effects of glucagon on transepithelial Na+, Cl−, K+, Ca2+ and Mg2+ net fluxes were investigated in isolated perfused cortical (cTAL) and medullary (mTAL) thick ascending limbs of Henle's loop of the mouse nephron. Transepithelial ion net fluxes (J Na +,J Cl −,J K +,J Ca 2+,J Mg 2+) were determined by electron probe analysis of the collected tubular fluid. Simultaneously the transepithelial voltage (PDte) and the transepithelial resistance (R te) were recorded. In cTAL-segments (n=8), glucagon (1.2×10−8 mol · l−1) stimulated significantly the reabsorption of Na+, Cl−, Ca2+ and Mg2+∶J Na + increased from 204±20 to 228±23 pmol · min−1 · mm−1,J Cl − from 203±18 to 234±21 pmol · min−1 · mm−1,J Ca 2+ from 0.52±0.13 to 1.34±0.30 pmol · min−1 · mm−1 andJ Mg 2+ from 0.51±0.08 to 0.84±0.08 pmol · min−1 · mm−1.J K+ remained unchanged: 3.2±1.3 versus 4.0±1.9 pmol · min−1 · mm−1. Neither PDte (16.3±1.5 versus 15.9±1.4 mV) norR te (22.5±3.0 versus 20.3±2.6 Ωcm2) were changed significantly by glucagon. However, in the post-experimental periods a significant decrease in PDte and increase inR te were noted. In mTAL-segments (n=9), Mg2+ and Ca2+ transports were close to zero and glucagon elicited no significant effect. The reabsorptions of Na+ and Cl−, however, were strongly stimulated:J Na + increased from 153±17 to 226±30 pmol · min−1 · mm−1 andJ Cl − from 151±23 to 243±30 pmol · min−1 · mm−1. The rise in NaCl transport was accompanied by an increase in PDte from 10.3±1.1 to 12.3±1.2 mV and a decrease inR te from 19.1±2.7 to 17.8±2.0 Ωcm2. No net K+ movement was detectable either in the absence or in the presence of glucagon. A micropuncture study carried out in hormone-deprived rats indicated that glucagon stimulates Na+, Cl−, K+, Mg2+ and Ca2+ reabsorptions in the loop of Henle. In conclusion our data demonstrate that glucagon stimulates NaCl reabsorption in the mTAL segment and to a lesser extent in the cTAL segment whereas it stimulates Ca2+ and Mg2+ reabsorptions only in the cortical part of the thick ascending limb of the mouse nephron. These data are in good agreement with, and extend, those obtained in vivo on the rat with the hormone-deprived model.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00582129
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