AJP - Cell Physiology, Vol 236, Issue 5 192-C201, Copyright © 1979 by American Physiological Society
Effect of microvibration on activity of ureteral and portal smooth muscles
T. Ohhashi, T. Azuma and M. Sakaguchi
Spontaneous contractions were elicited by microvibrations (1--80 Hz,
50--400 micron) imposed upon quiescent ureter and portal venous smooth
muscles of dogs. The microvibrations increased the rate of spontaneous
contractions. A microvibration of larger amplitude gave rise to a more
profound increase at each frequency. The acceleration was often accompanied
by a reduction in contractile force. The positive chronotropic effect was
enhanced by increases in frequency from 20 to 40 Hz and not affected by
administration of autonomic blocking agents and tetrodotoxin, but
disappeared in a Ca-free environment and reappeared on addition of Ba2+.
the simulating action of microvibration was almost proportional to external
Ca2+ concentrations ranging from 2.2 to 6.2 mM. The microvibrations were
able to elicit spontaneous activity in the preparation, which had been made
quiescent by administration of Mn2+. These findings suggested that the
positive chronotropic effect may be closely related to an increased Ca2+
influx through the membrane of smooth muscle. Active tension in the ureter
in a state of contracture was depressed by imposed microvibrations.
