Protamine augments stretch induced calcium increase in vascular endothelium.
1. Human umbilical vein endothelial cells cultured on a transparent silicone chamber were subjected to a short stretch pulse (ca. 1 s, 5-25% stretch) of their substrate and following increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) were measured by fluorescence intensity ratiometry using fura-2. 2. In response to mechanical stretch, the cells in HEPES buffered saline exhibited a Ca(2+) transient in a dose dependent way. The response was completely dependent on external Ca(2+) and inhibited by gadolinium (Gd(3+)), suggesting that it was mediated by the activation of a stretch activated cation channel (SACatC). 3. Interestingly, the stretch induced Ca(2+) transient was significantly augmented in the presence of basic polypeptide, protamine. This augmented Ca(2+) response was inhibited neither by Gd(3+) nor by the deprivation of external Ca(2+), indicating that the SACatC is not responsible for this phenomenon. 4. In contrast, this augmentation was inhibited by depletion of intracellular Ca(2+) stores with thapsigargin or by the pretreatment with phospholipase inhibitors such as U73122 and manoalide. 5. These results suggest the presence of a metabotropic mechanoreceptor distinct from the SACatC in vascular endothelium. This augmented [Ca(2+)](i) increase may contribute to the vasodilating response induced by protamine during heparin neutralization in cardiac surgery.
Murase
K
K
Internal Medicine II, Nagoya University School of Medicine, 65 Tsurumai, Nagoya 466-8550, Japan.
Naruse
K
K
Kimura
A
A
Okumura
K
K
Hayakawa
T
T
Sokabe
M
M
D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004963:Estrenes / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D006801:Humans; D008345:Manganese / Q000378:metabolism; D011479:Protamines / Q000494:pharmacology*; D011760:Pyrrolidinones / Q000494:pharmacology; D013314:Stress, Mechanical; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors
D004963:Estrenes; D011479:Protamines; D011760:Pyrrolidinones; D013729:Terpenes; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D008345:Manganese; D019284:Thapsigargin; D005682:Gadolinium; C045673:manoalide; D002118:Calcium