Nh2-terminal inserted myosin ii heavy chain is expressed in smooth
muscle of small muscular arteries.
Disanto, Michael E., Robert H. Cox, Ze Wang, and Samuel Chacko.
Departments of Pathobiology, Physiology, and Division of Urology,
University of Pennsylvania
APStracts 3:0392C, 1996.
We demonstrate, using reverse transcriptase-polymerase chain reaction
(RT-PCR), that while abdominal aorta from rabbit consists almost
entirely of MHC mRNA with no insert at the 5'-terminal coding region,
the distributing arteries (femoral and saphenous) begin to show MHC
mRNA with the 21 nucleotide insert that encodes seven amino acids in
the ATP binding region located in the myosin head. The femoral/iliac
artery contains >50% inserted mRNA while the more distal
saphenous artery contains >80% inserted mRNA. This insert is
also present in the smooth muscle from rat tail artery, but absent in
the smooth muscle from rat aorta. The actin-activated ATPase activity
of myosin from the rabbit femoral/saphenous artery is 1.7 fold higher
than that of the myosin from the aorta. A concomitant increase (about
2-fold) in the maximum shortening velocity of the saphenous artery,
compared to that of the aorta, indicates that the preponderance of
the inserted myosin is associated with both an increase in the actin
-activated ATPase activity and a larger maximum velocity of
shortening. Furthermore, analysis of the 17 kDa essential light chain
from the aorta reveals near equal quantities of the 17 kDa light
chain isoforms a & b, while the myosin from the femoral/saphenous
artery contains predominantly the 17 kDa a light chain isoform. Taken
together, these data indicate that the smooth muscle cells from the
small distributing arteries are similar to those of visceral smooth
muscle with respect to the expression of myosin isoforms, actin
-activated myosin ATPase activity, and contractility.
Received 1 July 1996; accepted in final form 4 December 1996.
APS Manuscript Number C370-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996