scholarly journals Testosterone inhibits the prostaglandin F2alpha-mediated increase in intracellular calcium in A7r5 aortic smooth muscle cells: evidence of an antagonistic action upon store-operated calcium channels

2003 ◽  
Vol 178 (3) ◽  
pp. 381-393 ◽  
Author(s):  
RD Jones ◽  
LN Ruban ◽  
IE Morton ◽  
SA Roberts ◽  
KM English ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Calcium Channels ◽  
Smooth Muscle Cells ◽  
Calcium Channel ◽  
Intracellular Calcium ◽  
Muscle Cells ◽  
Extracellular Calcium ◽  
Testosterone Replacement Therapy ◽  
Antagonistic Action ◽  
Prostaglandin F

Testosterone-induced vasodilatation is proposed to contribute to the beneficial effects associated with testosterone replacement therapy in men with cardiovascular disease, and is postulated to occur via either direct calcium channel blockade, or through potassium channel activation via increased production of cyclic nucleotides. We utilised flow cytometry to investigate whether testosterone inhibits the increase in cellular fluorescence induced by prostaglandin F(2alpha) in A7r5 smooth muscle cells loaded with the calcium fluorescent probe indo-1-AM, and to study the cellular mechanisms involved. Two-minute incubation with testosterone (1 microM) significantly inhibited the change in cellular fluorescence in response to prostaglandin F(2alpha) (10 microM) (3.6+/-0.6 vs 7.6+/-1.0 arbitrary units, P=0.001). The change in cellular fluorescence in response to prostaglandin F(2alpha) (10 microM) was also significantly attenuated in the absence of extracellular calcium (3.6+/-0.3 vs 15.6+/-0.7 arbitrary units, P=0.0000002), and by a 2-min incubation with the store-operated calcium channel blocker SK&F 96365 (50 microM) (4.7+/-0.8 vs 8.1+/-0.4 arbitrary units, P=0.003). The response was insensitive to similar incubation with the voltage-operated calcium channel blockers verapamil (10 microM) (12.6+/-1.2 vs 11.9+/-0.2 arbitrary units, P=0.7) or nifedipine (10 microM) (13.9+/-1.3 vs 13.3+/-0.5 arbitrary units, P=0.7). Forskolin (1 microM) and sodium nitroprusside (100 microM) significantly increased the cellular concentration of cyclic adenosine monophosphate and cyclic guanosine monophosphate respectively, but testosterone (100 nM-100 microM) had no effect. These data indicate that the increase in intracellular calcium in response to prostaglandin F(2alpha) occurs primarily via extracellular calcium entry through store-operated calcium channels. Testosterone inhibits the response, suggesting an antagonistic action upon these channels.

Dihydropyridine-sensitive single calcium channels in airway smooth muscle cells

1990 ◽  
Vol 259 (6) ◽  
pp. L468-L480 ◽  
Author(s):  
J. F. Worley ◽  
M. I. Kotlikoff
Keyword(s):  
Smooth Muscle ◽  
Calcium Channels ◽  
Smooth Muscle Cells ◽  
Calcium Channel ◽  
Airway Smooth Muscle ◽  
Muscle Cells ◽  
Membrane Depolarization ◽  
Airway Smooth Muscle Cells ◽  
Voltage Dependent ◽  
Voltage Dependent Calcium Channels

We have identified and characterized single voltage-dependent calcium channels in both acutely dissociated rat bronchial and cultured human tracheobronchial smooth muscle cells using the patch-clamp technique. In both cell types, on-cell membrane patches displayed unitary currents selective for barium ions and exhibited one conductance level (21–26 pS), and the open state probability was increased by membrane depolarization. Unitary barium currents were enhanced by the calcium channel selective agonist, BAY R 5417, and inhibited by the dihydropyridine calcium channel antagonist, nisoldipine (apparent inhibition constant less than 100 nM). Moreover, the degree of nisoldipine inhibition of the rat bronchial smooth muscle channels was increased with membrane depolarization in a manner consistent with the drug interacting with highest affinity to the inactivated channel state. In addition, the sensitivity to BAY R 5417 augmentation and nisoldipine inhibition of depolarization-induced tonic force of intact rat bronchial ring segments was in close agreement to the single channel results. Thus these data suggest that activation of voltage-dependent calcium channels can influence airway contraction and that dihydropyridines may be effective modulators of depolarization-induced increases in bronchial tone. We conclude that both rat and human airway smooth muscle cells have high-conductance voltage-dependent calcium channels that interact in a predictable manner with dihydropyridines and are similar to voltage-dependent calcium channels observed in other smooth muscle cells.

Contractile agonists activate voltage-dependent calcium channels in airway smooth muscle cells

1992 ◽  
Vol 263 (1) ◽  
pp. C106-C113 ◽  
Author(s):  
M. Tomasic ◽  
J. P. Boyle ◽  
J. F. Worley ◽  
M. I. Kotlikoff
Keyword(s):  
Smooth Muscle ◽  
Calcium Channels ◽  
Smooth Muscle Cells ◽  
Calcium Channel ◽  
Airway Smooth Muscle ◽  
Muscle Cells ◽  
Cell Types ◽  
State Probability ◽  
Airway Smooth Muscle Cells ◽  
Channel Currents

To determine whether agents that cause contraction of airway smooth muscle affect sarcolemmal calcium channel activity, unitary calcium channel currents (using Ba2+ as the charge carrier) were recorded in on-cell configuration from acutely dissociated (dog, pig, and ferret) and cultured (human) airway smooth muscle cells. Addition of the contractile agonists methacholine or bradykinin increased the open-state probability of the large-conductance calcium channel 37.2- and 45-fold, respectively. The increase in open-state probability was not due to cellular depolarization because increases occurred in the absence of depolarization. Channel activation by the agonist was determined to result in the favoring of a long (16.5 +/- 5.0 ms) open lifetime for the channel, which was not observed under control conditions, in the absence of BAY K 8644. We also report the unitary calcium channel currents from a second, smaller conductance calcium channel. This channel was present in all cell types and had a mean conductance of 9.5 +/- 0.8 pS (80 mM Ba2+). Exposure of cells to agonist also resulted in an increase in the open-channel probability of the small-conductance calcium channel (10.4-fold), which did not result from cellular depolarization. These experiments demonstrate that the molecular pathways exist between contractile agonist receptors and sarcolemmal calcium channels in airway smooth muscle cells. Because membrane patches were not directly exposed to agonist, receptor-channel linkage probably occurs via a second messenger-coupling pathway.

Fetuin-A uptake in bovine vascular smooth muscle cells is calcium dependent and mediated by annexins

2007 ◽  
Vol 292 (2) ◽  
pp. F599-F606 ◽  
Author(s):  
Neal X. Chen ◽  
Kalisha D. O'Neill ◽  
Xianming Chen ◽  
Danxia Duan ◽  
Exing Wang ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Intracellular Calcium ◽  
Vascular Smooth Muscle Cells ◽  
Muscle Cells ◽  
Extracellular Calcium ◽  
Fetuin A ◽  
Calcium Dependent

Fetuin-A is a known inhibitor of vascular calcification in vitro. In arteries with calcification, there is increased immunostaining for fetuin-A. However, vascular smooth muscle cells (VSMC) do not synthesize fetuin-A, suggesting fetuin-A may be endocytosed to exert its inhibitory effects. To examine the mechanism by which fetuin-A is taken up in bovine VSMC (BVSMC), we examined living cells by confocal microscopy and determined the uptake of Cy5-labeled fetuin-A. The results demonstrated that fetuin-A was taken up in BVSMC only in the presence of extracellular calcium, whereas phosphorus had no effect. Additional studies demonstrated the calcium-dependent uptake was specific for fetuin-A and only observed in BVSMC and osteoblasts, but not epithelial, endothelial, or adipose cells. The uptake was dose dependent, but could not be inhibited by excess unlabeled fetuin-A, suggesting a fluid phase rather than a receptor-mediated process. Fetuin-A also induced a sustained increase in intracellular calcium in BVSMC in the presence of extracellular calcium, whereas there was no increase in the absence of extracellular calcium. To further characterize the uptake, we utilized an inhibitor of annexin calcium channel activity, demonstrating inhibition of both fetuin-A uptake and intracellular calcium increase. Finally, we demonstrate that fetuin-A binds to annexin II at the cell membrane of BVSMC. In summary, our study demonstrates calcium- and annexin-dependent uptake of fetuin-A that leads to a sustained rise in intracellular calcium. This regulated uptake may be a mechanism by which fetuin-A inhibits VSMC calcification in the presence of excess calcium.

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