AJP - Cell Physiology, Vol 259, Issue 3 C484-C489, Copyright © 1990 by American Physiological Society
Protein content and myosin light chain phosphorylation in uterine arteries during pregnancy
D. J. Annibale, C. R. Rosenfeld, J. T. Stull and K. E. Kamm
Department of Pediatrics, University of Texas, Southwestern Medical Center, Dallas 75235.
During pregnancy, the ovine uterine artery changes from a low- to a
high-stress artery. We investigated the hypotheses that the increased
stress reflects alterations in vessel wall cellularity, smooth muscle cell
contractile protein contents, or activation properties. Uterine artery
diameter increased during pregnancy, whereas the fractional cellular
composition and thickness of the muscularis were unchanged. Results of
morphometry suggest that vessel growth is associated with cell elongation.
Uterine arteries from pregnant ewes had greater protein contents than those
from nonpregnant ewes (104 vs. 69 mg/g, respectively); there were
corresponding increases in the absolute cellular contents of actin and
myosin. While the fraction of light chain phosphorylated in response to
phenylephrine was unaltered, the total amount of myosin light chain
phosphorylated per gram wet weight increased significantly during
pregnancy. In addition, the distribution of myosin heavy chain isoforms was
also altered during pregnancy. The increased stress observed in the uterine
artery during ovine pregnancy reflects, in part, increases in cellular
contractile protein concentrations associated with hypertrophy.
