TY - JOUR
T1 - Norepinephrine and GTP-γ-S increase myofilament Ca2+ sensitivity in α-toxin permeabilized arterial smooth muscle
AU - Nishimura, Junji
AU - Kolber, Michael
AU - van Breemen, Cornelis
N1 - Funding Information:
We are particularly indebted to Dr. RJ. Hohman for supplying us with a-toxin and to the NIH (RO1 HL 40184) for grant support. The authors thank Gerry Trebilcock for her secretarial assistance.
PY - 1988/12/15
Y1 - 1988/12/15
N2 - A new method for preparing permeabilized smooth muscle fibers from rabbit mesenteric artery has been developed using α-toxin, a transmembrane pore-making exo-protein produced by Staphylococcus aureus. After α-toxin treatment the fibers developed tension as a function of Ca2+ concentration (EC50 = 890 nM). But they could not contract without added ATP, indicating ATP is permeable. When the sarcoplasmic reticulum was loaded with 5×10-7 M Ca2+ solution, NE induced a transient contraction in 2 mM EGTA 0 M Ca2+ solution and a transient and maintained contraction in 5×10-7 M Ca2+ solution. GTP-γ-S, a non-hydrolyzable analogue of GTP, substituted for NE in producing these contractile effects. The analysis of the relationship between Ca2+ and maintained tension revealed that NE and GTP-γ-S cause increases in Ca2+ sensitivity of myofilament shifting the EC50 to 280 nM and 160 nM, respectively. We conclude that NE or GTP-γ-S causes an increase in myofilament Ca2+ sensitivity and that G protein may be involved in receptor signal transduction system. α-Toxin is a useful tool to permeabilize the smooth muscle tissue to ions and small molecules without any damage of receptor and signal transduction system.
AB - A new method for preparing permeabilized smooth muscle fibers from rabbit mesenteric artery has been developed using α-toxin, a transmembrane pore-making exo-protein produced by Staphylococcus aureus. After α-toxin treatment the fibers developed tension as a function of Ca2+ concentration (EC50 = 890 nM). But they could not contract without added ATP, indicating ATP is permeable. When the sarcoplasmic reticulum was loaded with 5×10-7 M Ca2+ solution, NE induced a transient contraction in 2 mM EGTA 0 M Ca2+ solution and a transient and maintained contraction in 5×10-7 M Ca2+ solution. GTP-γ-S, a non-hydrolyzable analogue of GTP, substituted for NE in producing these contractile effects. The analysis of the relationship between Ca2+ and maintained tension revealed that NE and GTP-γ-S cause increases in Ca2+ sensitivity of myofilament shifting the EC50 to 280 nM and 160 nM, respectively. We conclude that NE or GTP-γ-S causes an increase in myofilament Ca2+ sensitivity and that G protein may be involved in receptor signal transduction system. α-Toxin is a useful tool to permeabilize the smooth muscle tissue to ions and small molecules without any damage of receptor and signal transduction system.
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U2 - 10.1016/S0006-291X(88)80303-6
DO - 10.1016/S0006-291X(88)80303-6
M3 - Article
C2 - 2849434
AN - SCOPUS:0024217418
VL - 157
SP - 677
EP - 683
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
SN - 0006-291X
IS - 2
ER -