The purpose of the current experiments was 1) to assess basolateral Na+-K+-2Cl-cotransporter (NKCC1) expression and 2) to ascertain the role of cystic fibrosis transmembrane conductance regulator (CFTR) in the regulation of this transporter in a prototypical pancreatic duct epithelial cell line. Previously validated human pancreatic duct cell lines (CFPAC-1), which exhibit physiological feature...

PURPOSE To determine whether the Na+-K+-2Cl- symport or the parallel Na+/H+ and Cl-/HCO3- antiports provide the dominant pathway for NaCl uptake into the ciliary epithelium. Both pathways are known to support NaCl entry from the stroma into the pigmented ciliary epithelial (PE) cells, after which Na+ and Cl- diffuse across the gap junctions into the nonpigmented ciliary epithelial (NPE) cells a...

We present a model for the control of the transmembrane potential of mammalian skeletal muscle cell. The model involves active and passive transport of Na(+), K(+), and Cl(-). As we check the model against experimental measurements on murine skeletal muscle cells, we find that the model can account for the observed bistability of the transmembrane potential at low extracellular potassium concen...

Ecelbarger, Carolyn A., Shuhua Yu, Alanna J. Lee, Lee S. Weinstein, and Mark A. Knepper. Decreased renal Na-K-2Cl cotransporter abundance in mice with heterozygous disruption of the Gsa gene. Am. J. Physiol. 277 (Renal Physiol. 46): F235–F244, 1999.—Transport processes along the nephron are regulated in part by hormone stimulation of adenylyl cyclases mediated by the heterotrimeric G protein Gs...

ANG II is a modulator of tubuloglomerular feedback (TGF); however, the site of its action remains unknown. Macula densa (MD) cells sense changes in luminal NaCl concentration ([NaCl](L)) via a Na-2Cl-K cotransporter, and these cells do possess ANG II receptors. We tested whether ANG II regulates Na-2Cl-K cotransport in MD cells. MD cell Na(+) concentration ([Na(+)](i)) was measured using sodium...

We have recently disrupted Slc12a2, the gene encoding the secretory Na-K-2Cl cotransporter in mice (NKCC1) (Delpire et al., 1999). Gramicidin perforated-patch and whole-cell recordings were performed to study GABA-induced currents in dorsal root ganglion (DRG) neurons isolated from wild-type and homozygote NKCC1 knock-out mice. In wild-type DRG neurons, strong GABA-evoked inward current was obs...

The mechanisms of K(+) entry from the hemolymph into principal cells of Malpighian tubules were investigated in the yellow fever mosquito, Aedes aegypti. The K(+) channel blocker Ba(2+) (5 mmol l(-1)) significantly decreased transepithelial (TEP) fluid secretion (V(s)) from 0.84 nl min(-1) to 0.37 nl min(-1) and decreased the K(+) concentration in secreted fluid from 119.0 mmol l(-1) to 54.3 mm...

The volume of certain subpopulations of trabecular meshwork (TM) cells may modify outflow resistance of aqueous humor, thereby altering intraocular pressure. This study examines the contribution that Na+/H+, Cl-/HCO exchange, and K+-Cl- efflux mechanisms have on the volume of TM cells. Volume, Cl- currents, and intracellular Ca2+ activity of cultured human TM cells were studied with calcein flu...

The mechanotransduction of vestibular sensory cells depends on the high endolymphatic potassium concentration ([K+]) maintained by a fine balance between K+ secretion and absorption by epithelial cells. Despite the crucial role of endolymph as an electrochemical motor for mechanotransduction, little is known about the processes that govern endolymph formation. To address these, we took advantag...

Vasoconstrictors activate the Na(+)-K(+)-2Cl(-) cotransporter NKCC1 in rat aortic smooth muscle, but the mechanism is unknown. Efflux of (86)Rb(+) from rat aorta in response to phenylephrine (PE) was measured in the absence and presence of bumetanide, a specific inhibitor of NKCC1. Removal of extracellular Ca(2+) completely abolished the activation of NKCC1 by PE. This was not due to inhibition...