AJP - Regulatory, Integrative and Comparative Physiology, Vol 262, Issue 5 895-R900, Copyright © 1992 by American Physiological Society
Stretch-mediated visceral smooth muscle growth in vitro
O. M. Karim, K. Pienta, N. Seki and J. L. Mostwin
James Buchanan Brady Urological Institute, Johns Hopkins Hospital, Baltimore, Maryland 21205.
An in vitro model of smooth muscle stretch was developed to study
mechanical stimulus as a possible mediator of visceral smooth muscle growth
and differences in the growth response of smooth muscle from young and old
animals. De novo DNA synthesis as measured by the aphidicolin-sensitive
specific activity of DNA was used as an index of cell growth. Compared with
old tissue, the rate of aphidicolin-sensitive DNA synthesis in smooth
muscle from young animals was 3-5 and 1.5-2 times greater in bladder and
taenia coli, respectively. Stretch of bladder muscle and taenia coli strips
from young animals for 6 h increased the aphidicolin-sensitive specific
activity of DNA 3-fold (P less than 0.01) and 1.5-fold (P less than 0.01),
respectively. Tissue from old animals, however, under the same conditions
increased the rate of aphidicolin-resistant DNA synthesis, possibly
implying DNA repair. Autoradiography showed only labeled myocyte nuclei.
These results indicate that homeostatic mechanisms modulating myocyte
growth in visceral smooth muscle can respond to mechanical stimulus in the
absence of other trophic factors.
