Naslov
Partial recovery of in vivo function by improved incubation conditions of isolated renal proximal tubule. I. Change of amiloride-inhibitable K(+) conductance

Autori
Mueller-Berger, S. ; Coppola, S. ; Samaržija, Ita ; Seki, G. ; Froemter, Eberhard

Izvornik
Pflügers Archiv (0031-6768) 434 (1997), 4; 373-382

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
isolated renal proximal tubule; metabolic substrates; Na/K pump; amiloride-inhibitable K(+) conductance

Sažetak
Isolated microperfused rabbit renal proximal tubule S2 segments, if incubated in conventional substrate containing HCO3- Ringer solution, exhibit lower cell membrane potentials (Vb) and elevated intracellular Na(+) concentrations(/Na/i) compared to rat tubules in vivo. Assuming that these and other differences reflect insufficient metabolic and/or hormonal stimulation of the cells, we have used microelectrode techniques to test whether improving substrate supply and applying norepinephrine (NE, to compensate for the missing nerve supply) reverts Vb and /Na/i to values observed in vivo. Application of D-glucose (5.5 mmol/l) and additional application of pyruvate, lactate, or L-alanine (each 10 mmol/l), or bathing the tubules in Dulbecco's modified Eagle's tissue culture medium (DMEM) significantly increased Vb and, whenever tested, reduced /Na/i as compared to substrate-free or D-glucose-containing control solution and these effects could be prevented - as test in the case of pyruvate - by inhibition of the Na/K pump with ouabain. However, high concentrations of acetate, beta-hydroxybutyrate, or L-glutamine had no significant effect. The largest effect was obtained with joint application of DMEM and NE (10 micromol/l) with increased Vb from -42.8 +/- 1.3 mV (SEM) to -55.3 +/- 2.5 mV (n=11). Interestingly we noticed that under the latter conditons the Vb response to bath application of 1 mmol7l amiloride virtually disappeared, i.e. it changed from a depolarization of +14.6 +/- 1.4 mV (in D-glucose Ringer solution) to +0.6 +/- 0.7 mV (in DMEM plus NE) (n=8), with some tubules showing even a small hyperpolarization.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

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