Posted on Tue, Mar 06, 2012
Congratulations to Sandeep Khurana M.B.B.S., Hema Raina M.B.B.S., M.D., Ph.D., Valeria Pappas Ph.D., Jean-Pierre Raufman M.D., and Thomas L Pallone M.D., for their recent publication:
Khurana S, Raina H, Pappas V, Raufman J-P, Pallone TL (2012) Effects of Deoxycholylglycine, a Conjugated Secondary Bile Acid, on Myogenic Tone and Agonist-Induced Contraction in Rat Resistance Arteries. PLoS ONE 7(2): e32006. doi:10.1371/journal.pone.0032006
Background
Bile acids (BAs) regulate cardiovascular function via diverse mechanisms. Although in both health and disease serum glycine-conjugated BAs are more abundant than taurine-conjugated BAs, their effects on myogenic tone (MT), a key determinant of systemic vascular resistance (SVR), have not been examined.
doi:info:doi/10.1371/journal.pone.0032006.g005
Methodology/Principal Findings
Fourth-order mesenteric arteries (170–250 µm) isolated from Sprague-Dawley rats were pressurized at 70 mmHg and allowed to develop spontaneous constriction, i.e., MT. Deoxycholylglycine (DCG; 0.1–100 µM), a glycine-conjugated major secondary BA, induced reversible, concentration-dependent reduction of MT that was similar in endothelium-intact and -denuded arteries. DCG reduced the myogenic response to stepwise increase in pressure (20 to 100 mmHg). Neither atropine nor the combination of L-NAME (a NOS inhibitor) plus indomethacin altered DCG-mediated reduction of MT. K+ channel blockade with glibenclamide (KATP), 4-aminopyradine (KV), BaCl2 (KIR) or tetraethylammonium (TEA, KCa) were also ineffective. In Fluo-2-loaded arteries, DCG markedly reduced vascular smooth muscle cell (VSM) Ca2+ fluorescence (~50%). In arteries incubated with DCG, physiological salt solution (PSS) with high Ca2+ (4 mM) restored myogenic response. DCG reduced vascular tone and VSM cytoplasmic Ca2+ responses (~50%) of phenylephrine (PE)- and Ang II-treated arteries, but did not affect KCl-induced vasoconstriction.
doi:info:doi/10.1371/journal.pone.0032006.g005
Conclusion
In rat mesenteric resistance arteries DCG reduces pressure- and agonist-induced vasoconstriction and VSM cytoplasmic Ca2+ responses, independent of muscarinic receptor, NO or K+ channel activation. We conclude that BAs alter vasomotor responses, an effect favoring reduced SVR. These findings are likely pertinent to vascular dysfunction in cirrhosis and other conditions associated with elevated serum BAs.
doi:info:doi/10.1371/journal.pone.0032006.g005
Calcium fluorescence
In experiments where a Ca2+ indicator was used, the selected artery was exposed to dissection solution containing Fluo-2 (TEFLabs, 7.5 µM), 1.5% DMSO (vol/vol), and 0.03% cremophor EL (vol/vol) for 1 h at room temperature. After 1 h, the arteries were cannulated as described above and allowed to develop MT for 30 min. Arteries were imaged with a confocal scanning inverted microscope (×60, 1.4 NA, water-immersion objective). Images of fluo-2-loaded fluorescent VSM were obtained with an intensified CCD camera (Stanford Photonics, Palo Alto, CA, USA) coupled to a Nipkow spinning disk confocal microscope with 488 nm excitation. Spatially resolved information on cytoplasmic [Ca2+] was obtained in individual VSM cells. To quantify changes, fluo-2 fluorescence (F) was normalized to its initial value (F0) in each cell.
doi:info:doi/10.1371/journal.pone.0032006.g005
Figure 5. DCG reduces VSM Ca2+ in 4th-order mesenteric arteries from rats with MT.
Ca2+ fluorescence was measured in Fluo-2-loaded arteries before and after incubating with DCG 100 µM for 5 minutes. DCG reduced the arterial VSM Ca2+ fluorescence by ~50%. (n = 3 arteries in each group).
doi:info:doi/10.1371/journal.pone.0032006.g005
Copyright Khurana et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Effects of Deoxycholylglycine, a Conjugated Secondary Bile Acid, on Myogenic Tone and Agonist-Induced Contraction in Rat Resistance Arteries
Posted on Mon, Jun 20, 2011
TEFlabs has the lowest prices ever for Fluo-8. Beat the heat this summer, spend more time indoors performing experiments using Fluo-8. (expires 10-1-2011)
#0201 TEFlabs Fluo-8 (AM) 1 mg $50
#0203 TEFlabs Fluo-8 (AM) 20 x 50 ug $60
#0205 TEFlabs Fluo-8 (K+Salt) 1 mg $50
While Fluo-8 is marketed under a variety of names, the original patent outlining Fluo-2 medium affinity (Fluo-8) published in 1991. The original journal publication appeared in the Journal of Biological Chemistry in 1989. Why pay a premium for 20 year old indicator technology?
Some companies will charge $245 or more per mg, TEFLabs has been making Fluo dyes since 1988 and has more Fluo experience than any of our competitors, our experience and expertise at manufacturing Fluo dyes allows us to offer Fluo-8 at much lower cost to researchers. Dont let other manufacturers inexperience cost you money!
Read the original Fluo paper:
Fluorescent Indicators for Cytosolic Calcium based on Rhodamine and Fluorescein Chromophores
