Complex stiffness of smooth muscle cytoplasm in the presence of Ca-activated brevin.
Brevin, an F-actin severing protein, regulates actin gel-sol transformation in a Ca(2+)-dependent way. Here, we tested its effect on the stiffness of the cytoplasm of skinned smooth muscle, in the absence of actin-myosin interaction (inhibited myosin ATPase). Complex stiffness was measured by imposing sinusoidal stretches and releases at different frequencies (1-50 Hz). In the presence of Ca-activated brevin, the stiffness decreased by about 30%, at all frequencies, from its initial values in Ca-free, relaxing solution. This decrease reflected a fall in both elasticity and viscosity of the cytoplasm. We propose that brevin specifically operates on an actin network in parallel with the contractile apparatus, e.g. on the actin-filamin gel.
Gailly
P
P
Département de Physiologie, Université Catholique de Louvain, Bruxelles, Belgium.
Gillis
J M
JM
Capony
J P
JP
D000199:Actins / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003106:Colon; D003593:Cytoplasm; D004558:Electric Stimulation; D018260:Gelsolin; D006168:Guinea Pigs; D008634:Mersalyl / Q000494:pharmacology; D008840:Microfilament Proteins / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000648:ultrastructure*; D009218:Myosins / Q000037:antagonists & inhibitors; D011193:Potassium Iodide / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
D000199:Actins; D018260:Gelsolin; D008840:Microfilament Proteins; C016953:brevin; D011193:Potassium Iodide; D014638:Vanadates; D008634:Mersalyl; D009218:Myosins; D002118:Calcium