An acute increase of peritubular K stimulates K transport through cell pathways of CCT.
In this study, we have investigated net transport and electrical properties of isolated perfused cortical collecting ducts of control and DOCA-treated rabbits to clarify the cell mechanism for secreting K on an acute increase of peritubular K concentration. Raising bath K in control experiments caused an increase in net K secretion (-JK) and net Na absorption (JNa). Barium (5 mM), a known blocker of basolateral K conductance, added to the bath had no effect on this transport stimulation. In the presence of luminal Ba (5 mM) -JK was reduced to zero, but JNa was unaltered. When bath K was increased -JK increased to a value slightly greater than zero, but not different from the predicted passive flux through the paracellular pathway. In tubules of DOCA-treated rabbits, raising K in the bath increased -JK and JNa. The observed stimulation of -JK was blunted in the presence of Ba in the bath, whereas the increase in JNa remained the same. Thus, in DOCA-treated tubules, Ba in the bath significantly attenuated the increase in K secretion without affecting the transport stimulation of JNa. When Ba was added to the perfusate and bath K increased, -JK, which was initially 22.1, increased to 36.4 pmol.mm-1.min-1. Thus a "Ba-insensitive" pathway became more evident in CCTs from DOCA-treated rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)
Muto
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Department of Physiology, Yale University School of Medicine, New Haven, Connecticut 06510.
Giebisch
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Sansom
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D000465:Algorithms; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001693:Biological Transport, Active; D003900:Desoxycorticosterone / Q000494:pharmacology; D005260:Female; D007684:Kidney Tubules / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D011817:Rabbits
D001464:Barium; D003900:Desoxycorticosterone; D011188:Potassium