As. Battistellapatterson et al., EFFECT OF DISRUPTION OF THE CYTOSKELETON ON SMOOTH-MUSCLE CONTRACTION, Canadian journal of physiology and pharmacology, 75(12), 1997, pp. 1287-1299
The relationship between passive tension applied to aortic rings and t
he resulting increase in tissue length was nearly linear over the rang
e of 1 to 15 g. However, even with increasing tissue length, within th
e range of 1 to 10 g passive tension, the total active force generated
upon stimulation was not significantly changed. These observations em
phasize the great flexibility of the mechanism(s) underlying the contr
actile response of vascular smooth muscle with regard to changes in ti
ssue preload and length. Neither the blockade of microtubule polymeriz
ation by colchicine nor the blockade of actin polymerization by cytoch
alasin B significantly changed the slope of the tissue length-preload
curve, indicating no effect on the tissues' capacity to stretch at a g
iven preload. With stimulation of the tissue at different levels of st
retch, colchicine caused an increase in the initial fast component of
active tension development, but partially blocked the secondary slow r
ise in tension. Cytochalasin B dramatically reduced the total contract
ile response at each preload studied, and this effect was confined alm
ost exclusively to the secondary slow increase in tension. When tissue
s were cooled to cause complete dissolution of the microtubule network
and then warmed in the presence of colchicine to prevent repolymeriza
tion of both the active and stable populations of microtubules, there
was also a significant reduction in the slow component of contraction
with no effect on the fast response. The partial blockade of synthesis
of the microtubule-associated motor protein kinesin by application of
an antisense oligonucleotide to aortae in situ or to aortic rings in
tissue culture significantly reduced the contractile response to potas
sium depolarization. The results suggest that the microtubules and the
actin filaments of the cytoskeleton play an active role in slow force
development as opposed to a solely passive role based on the effect o
f the static, structural properties of these filaments on mechanical r
esistance. We propose that a tension-bearing element of the actin-cont
aining cytoskeleton undergoes remodeling to adjust tension within the
system. The microtubules could act either through the directed movemen
t of the molecules involved in the transduction process or through the
direct action of kinesin-mediated intracytoskeletal interactions in f
orce development that involve a remodeling of the tension-bearing elem
ents of the cytoskeleton.