Back to Search Start Over

Mechanism of NaCl secretion in rectal gland tubules of spiny dogfish ( Squalus acanthias).

Mechanism of NaCl secretion in rectal gland tubules of spiny dogfish ( Squalus acanthias).

Authors :
Greger, Rainer
Schlatter, Eberhard
Source :
Pflügers Archiv: European Journal of Physiology; 1984, Vol. 402 Issue 4, p364-375, 12p
Publication Year :
1984

Abstract

Rectal gland tubule (RGT) segements of the spiny dogfish ( Squalus acanthias) were perfused in vitro. The effects of inhibitors of known mode of action on transepithelial PD (PD resistance (R), the PD across the basolateral membrane (PD), the fractional resistance of this membrane (FR), and intracellular activities of Na, Cl, K ( a) were examined. Furosemide (5·10 mol·l) reduced PD from −12±0.7 to −2.3±0.2 mV ( n=63), hyperpolarized PD from −71±1.3 to −79±0.9 mV ( n=59), FR decreased from 0.2±0.03 to 0.13±0.01 ( n=21), a fell from 38±4 to 11±2 mmol·l ( n=14), a fell from 37±4 to 17±2 mmol·l ( n=12) and a was constant [113±14 vs. 117±15 mmol·l ( n=6)]. Furosemide exerted its effects within some 20-40 s. Its action was completely reversible. Analysis of the time courses revealed that the furosemide induced initial fall in a was approximately twice as rapid when compared to that of a. Ba 0.5 mmol·l (bath) reduced PD from −7.4±1.2 to −4.1±0.6 mV ( n=24), increased R from 18±2 to 22±2.5, Ωcm ( n=14). PD depolarized from −75±2 to −48±2 mV ( n=42), FR increased from 0.2±0.02 to 0.34±0.04 ( n=14) and a increased from 143±28 to 188±40 mmol·l ( n=4). Ouabain (50·10 mol·l, bath) reduced PD from −12±2 to −3±0.5 mV ( n=9), R increased from 18±3 to 21±3 Ωcm ( n=5), PD depolarized from −67±4 to −26±3 mV ( n=14), FR increased from 0.23±0.04 to 0.45±0.05 ( n=6), a fell only slightly from 135±15 to 112±30 mmol·l ( n=4), but a increased from 35±12 to 111±37 mmol·l ( n=3). These effects of ouabain were slow when compared to those exerted by furosemide or Ba. The ouabain effects on PD and PD were completely prevented if furosemide was applied first. Amiloride (≤10 mol·l, both sides), and anthracene-9-carboxylate (≤10 mol·l, lumen) were devoid of effects on PD and PD. The stilbene disulfonate derivate SITS (≤10 mol·l, both sides) led to a 36±9% inhibition of PD. The present data, apart from supporting the cell model proposed in a preceding report, allow the following conclusions: The transient analysis of the furosemide effects is suggestive for a 2 Cl∶1 Na stoichiometry of the carrier. The furosemide induced reduction in FR suggests that the fall in aleads to a marked reduction in the apical Cl-conductance. Furosemide apparently drives a Cl/cell to passive distribution and PD to the K equilibrium potential. a then approaches a minimal value which is close to that present in nonstimulated RGT segments. Ba leads to an increase in a because it blocks the conductive recycling pathway for this ion. Ouabain does not only inhibit the (Na+K)-ATPase, it also reduces the K-conductance of the basolateral membrane. This explains why a stays high. The cell PD then is dominated by a. The Na 2ClK-carrier increases a further and the cell continues to depolarize. Thus, the depolarization of the cell is not a sign of K loss but indicative of Cl gain. In the presence of furosemide ouabain is devoid of any effect on PD, suggesting that the Na2 ClK-carrier is the only quantitatively important source of Na entry into the RGT cell. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00316768
Volume :
402
Issue :
4
Database :
Complementary Index
Journal :
Pflügers Archiv: European Journal of Physiology
Publication Type :
Academic Journal
Accession number :
73148602
Full Text :
https://doi.org/10.1007/BF00583937