Regulation by calcitonin of Na(+)-K(+)-Cl- cotransport in a rabbit thick ascending limb cell line

Abstract

The hormonal regulation of a Na(+)-K(+)-Cl- cotransport was investigated in a renal tubule cell line (RC.SV2 cells) transformed by the simian virus 40. This cell line has the main characteristics of cells from the thick ascending limb of Henle, including the presence of Tamm-Horsfall protein and stimulation of adenosine 3',5'-cyclic monophosphate (cAMP) production by calcitonin (CT). Kinetic studies with 22Na+, 36Cl-, and 86Rb+ indicated the existence of a Na(+)-K(+)-Cl- cotransport with a stoichiometry of 1Na+:1K+: 2Cl-. All compounds stimulating cAMP production enhanced the ouabain-resistant bumetanide-sensitive (Or-Bs) Rb+ influx mediated by Na(+)-K(+)-Cl- cotransport. CT (100 ng/ml) increased the Or-Bs influx twofold by enhancing maximum velocity without changing the apparent Michaelis constant. The K(+)-channel blocker barium blunted the CT-stimulated Or-Bs influx by 64-74%, whereas the Cl(-)-channel blocker 5-nitro-2-(3-phenylpropylamino)benzoate reduced the CT-stimulated influx by 28-40%. These results suggest that CT stimulates the Na(+)-K(+)-Cl- cotransport by a cAMP-dependent mechanism and that K+ recycling through K+ membrane channels is an important modulator of cotransporter-mediated ion fluxes.

Calcitonin-stimulated renal Ca2+ reabsorption occurs independently of TRPV5

“…In addition, the urinary Na + /K + ratio remained unchanged excluding an effect on the collecting duct. These data are consistent with a primary effect of CT on electrolyte transport in the TAL and DCT [5][6][7]17]. …”

“…This segment of the TAL is also thought to drive paracellular Ca 2+ reabsorption in these species. Al- though never delineated in detail, CT is likely to activate a cAMP cascade leading to increased NKCC2 transport, perhaps via increased membrane trafficking and phosphorylation [5,6,25]. Currently, it remains unknown which transporter CT stimulates in the DCT [17].…”

“…Administration of CT to rats increases the renal reabsorption of Ca 2+ , which is in part achieved by increasing the reabsorption of Ca 2+ in the TAL. Here, application of CT also increases vectorial NaCl transport [5][6][7]. Active transcellular Ca 2+ transport is restricted to the distal convolutions.…”

“…Although the treatment has been much improved, the mortality rate may still be as high as 8% [1,3,4]. The experimental model for rhabdomyolysis is easily acquired by injecting glycerol intramuscularly into rats or mice [5].…”

The mechanism of action of the antidiuretic peptide Tenmo ADFa in Malpighian tubules ofAedes aegypti

“…In the thick ascending limb of the loop of Henle, this kind of functional coupling serves to recycle K + across the apical membrane. Apical membrane K + -channels return intracellular K + to the tubule lumen, thereby ensuring a sufficient K + supply for Na/K/2Cl cotransport across that membrane (Vuillemin et al, 1992), because glomerular filtration may not always present sufficient quantities of K + to the luminal face of the Na/K/2Cl cotransporter.…”