PHORBOL ESTER STIMULATION OF 250H-VITAMIN D 1-HYDROXYLASE ACTIVITY IN THE MONOBLASTIC CELL LINE U937

Vitamin D ◽  
1988 ◽  
pp. 360-361
Keyword(s):  
Vitamin D ◽  
Cell Line ◽  
Phorbol Ester ◽  
Hydroxylase Activity ◽  
Stimulation Of

scholarly journals Phorbol esters rapidly stimulate amiloride-sensitive Na+/H+ exchange in a human leukemic cell line.

1984 ◽  
Vol 99 (1) ◽  
pp. 340-343 ◽  
Author(s):  
J M Besterman ◽  
P Cuatrecasas
Keyword(s):  
Cell Line ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Leukemic Cell ◽  
Leukemic Cell Line ◽  
Human Leukemic Cell ◽  
Initial Event ◽  
Phorbol Ester Receptor ◽  
Human Leukemic Cell Line ◽  
Stimulation Of

The human, leukemic cell line, HL-60, undergoes differentiation in response to tumor-promoting phorbol esters. Recent studies have implicated stimulation of a Na+/H+ antiporter as an initial event in cellular differentiation and/or proliferation. The effects of phorbol esters on Na+-dependent H+ efflux from HL-60 cells were studied by pH-stat titration. Tumor-promoting phorbol diesters, but not the inactive parent alcohol, stimulated Na+-dependent H+ efflux in a rapid (within 1 min at 37 degrees C) and reversible manner. Stimulation was dependent on the concentration of extracellular sodium; lithium could substitute for sodium, but choline could not. Stimulation was dependent on the activity of extracellular protons and was inhibited completely by amiloride. The concentrations of phorbol diesters at which we observed half-maximal stimulation of Na+-dependent H+ efflux are very similar to the Kd reported in the literature for binding of these phorbol diesters to the phorbol ester receptor and the Km for phorbol diester activation of protein kinase C. Overall characterization of basal and phorbol ester-stimulated H+ efflux indicate that stimulation of a Na+/H+ antiporter constitutes a primary event in phorbol ester interaction with HL-60 cells.

scholarly journals Stimulation of choline release from NG108-15 cells by 12-O-tetradecanoylphorbol 13-acetate

1987 ◽  
Vol 241 (1) ◽  
pp. 81-86 ◽  
Author(s):  
M Liscovitch ◽  
J K Blusztajn ◽  
A Freese ◽  
R J Wurtman
Keyword(s):  
Cell Line ◽  
Phorbol Ester ◽  
Hybrid Cell ◽  
Water Soluble ◽  
Hybrid Cell Line ◽  
Maximal Effect ◽  
Methylation Pathway ◽  
Free Choline ◽  
Stimulation Of ◽  
Glioma Hybrid Cell

The effects of the potent tumour-promoting phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) on phosphatidylcholine (PtdCho) metabolism were investigated in the neuroblastoma X glioma hybrid cell line NG108-15. TPA (100 nM) stimulated by 150-200% the release into the medium of 3H radioactivity from cells that had been pre-labelled with [3H]choline. H.p.l.c. analysis of the medium revealed that TPA stimulated the release of only free [3H]choline (212 +/- 11% of control), without affecting such other labelled metabolites as [3H]phosphocholine and [3H]glycerophosphocholine. This effect was concentration-dependent, with a half-maximal effect obtained at 27.5 +/- 6.8 nM, and was observable as early as 5-10 min after exposure to TPA. The TPA-induced release of [3H]choline into the medium was accompanied by a small and variable decrease in cellular [3H]PtdCho (to 93 +/- 4% of control). However, the radioactivity associated with water-soluble cellular choline metabolites (mainly [3H]phosphocholine and [3H]glycerophosphocholine) remained unchanged. TPA also stimulated the release of [3H]choline derived from [3H]PtdCho that had been produced via the methylation pathway from [3H]methionine. These data suggest that phosphatidylcholine may serve as the source of free choline released from the cells in response to TPA. The possible enzymic mechanisms underlying this response are discussed.

scholarly journals Regulation of vitamin D metabolism by calcium and phosphate ions in isolated renal tubules

1981 ◽  
Vol 196 (1) ◽  
pp. 187-193 ◽  
Author(s):  
E Spanos ◽  
H Freake ◽  
S J MacAuley ◽  
I MacIntyre
Keyword(s):  
Vitamin D ◽  
Experimental Period ◽  
Renal Tubules ◽  
Long Term Effects ◽  
Hydroxylase Activity ◽  
Experimental Conditions ◽  
Vitamin D Metabolism ◽  
Stimulation Of

The acute and long-term effects of Ca2+ and Pi on vitamin D metabolism were studied in vitro with isolated renal tubules from vitamin D-deficient and vitamin D-supplemented chicks. Ca2+ depletion, achieved by isolating renal tubules in Ca2+-free buffers, led to suppression of 1 alpha-hydroxylase activity. Re-introduction of Ca2+ during incubation caused an acute stimulation of this enzyme. This stimulatory effect of Ca2+ was prevented by prior treatment of Ca2+-depleted renal tubules for 6 h with 1,25-dihydroxycholecalciferol. Ca2+ and Pi produced marked acute affects on 1 alpha-hydroxylase activity, which persisted for the whole 8 h experimental period, in Ca2+-depleted renal tubules from vitamin D-deficient chicks. The effects of either ion were influenced by the concentration of the other. However, the effects of these ions could not be reproduced in either Ca2+-depleted renal tubules from vitamin D-supplemented chicks or in renal tubules from vitamin D-deficient chicks, isolated in Ca2+-containing buffers. Isolation of renal tubules from vitamin D-supplemented chicks in Ca2+-containing buffers and subsequent incubation for 8 h in the presence of increased [Ca2+] led to a modest but statistically significant suppression of 1 alpha-hydroxylase and stimulation of 24-hydroxylase activity. It is concluded that the acute effects of Ca2+ and Pi on 1 alpha-hydroxylase activity of Ca2+-depleted renal tubules from vitamin D-deficient chicks are not regulatory but the results of the experimental conditions. In contrast the long-term effects of Ca2+ on both hydroxylases of renal tubules from vitamin D-supplemented chicks may be of physiological significance.

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