ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
The mechanism by which 86Rb+ (used as a tracer for K+) enters human nonpigmented ciliary epithelial cells were investigated. Ouabain-inhibitable bumetanide-insensitive 86Rb+ transport accounted for ∼70-80% of total, whereas bumetanide-inhibitable ouabain-insensitive uptake accounted for 15-25% of total. K+ channel blockers such as BaCl2 reduced uptake by ∼5%. Bumetanide inhibited 86Rb+ uptake with an IC50 of 0.5 μM, while furosemide inhibited with an IC50 of about 20 μM. Bumetanide-inhibitable 86Rb+ uptake was reduced in Na+-free or Cl--free media, suggesting that Na+ and Cl- were required for optimal uptake via this mechanism. These characteristics are consistent with a Na+, K+, Cl- contransporter in NPE cells. Treatment of NPE cells for 15 min with phorbol 12-myristate, 13-acetate (PMA), an activator of protein kinase C, caused a 50-70% decrease in 86Rb+ uptake via the Na+, K+, Cl- cotransporter. Other 86Rb+ uptake mechanisms were not affected. 86Rb+ uptake via the Na+, K+, Cl- contransporter could be inhibited by other phorbol esters and by dioctanoylglycerol, an analog of diacylglycerol, but not by 4α phorbol didecanoate, an ineffective activator of protein kinase C. Staurosporine, a protein kinase C inhibitor, blocked phorbol ester inhibition of 86Rb+ uptake. These data suggest that a Na+, K+, Cl- cotransporter in NPE cells is inhibited by activation of protein kinase C. © 1992 Wiley-Liss, Inc.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1041530126
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