The broad objective of my research is to determine the molecular mechanism(s) responsible for regulation of crossbridges and contraction in vascular smooth muscle. Contractile stimuli were originally hypothesized to regulate smooth muscle contraction only via [Ca2+]i/calmodulin-dependent activation of myosin light chain kinase (MLCK). Activated MLCK is known to phosphorylate the 20 Kd light chain of myosin. Myosin light chain phosphorylation appears to be the primary determinant of force production. However, we found that myosin phosphorylation levels depend on both changes in [Ca2+]i and the stimulus employed. KC1 depolarization of intact smooth muscle tissues induced relatively larger increases in [Ca2+]i and relatively smaller increases in myosin phosphorylation than were observed with histamine stimulation (i.e. depolarization was associated with a lower [Ca2+]i sensitivity than was observed with histamine stimulation). There are four possible mechanisms that could explain changes in [Ca2+]i sensitivity: 1) the Ca2+-sensitivity of MLCK could be altered (e.g. by phosphorylation of MLCK), 2) myosin light chain phosphatase could be regulated, 3) [Ca2+]i estimates may be inaccurate, and/or 4 myosin could be phosphorylated by another kinase. The primary objective of this proposal is to determine the molecular mechanism(s) responsible for the alterations in [Ca2+]i sensitivity observed in intact vascular smooth muscle.
The Specific Aims are to: 1) administratively deleted. 2) Test the hypothesis that aequorin accurately estimates myoplasmic [Ca2+] in intact tissues. We will measure myoplasmic [Ca2+] with both aequorin and Fura 2 in intact tissues. 3) Test the hypothesis that a G protein is involved in regulating [Ca2+]i sensitivity. We will inhibit G proteins with pertussis toxin or intracellularly loaded GDP-beta-S an evaluate the effect on [Ca2+]i and [Ca2+]i sensitivity.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Physiology Study Section (PHY)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Virginia
Schools of Medicine
United States
Zip Code
van Riper, D A; McDaniel, N L; Rembold, C M (1997) Myosin light chain kinase phosphorylation in nitrovasodilator induced swine carotid artery relaxation. Biochim Biophys Acta 1355:323-30
Chen, X L; Panek, K; Rembold, C M (1997) Metformin relaxes rat tail artery by repolarization and resultant decreases in Ca2+ influx and intracellular [Ca2+]. J Hypertens 15:269-74
Rembold, C M; Weaver, B A (1997) Tyrosine phosphorylation and regulation of swine carotid artery contraction. J Vasc Res 34:1-10
Chen, X L; Rembold, C M (1996) Nitroglycerin relaxes rat tail artery primarily by lowering Ca2+ sensitivity and partially by repolarization. Am J Physiol 271:H962-8
Van Riper, D A; Chen, X L; Gould, E M et al. (1996) Focal increases in [Ca2+]i may account for apparent low Ca2+ sensitivity in swine carotid artery. Cell Calcium 19:501-8
Gould, E M; Rembold, C M; Murphy, R A (1995) Genistein, a tyrosine kinase inhibitor, reduces Ca2+ mobilization in swine carotid media. Am J Physiol 268:C1425-9
Van Riper, D A; Weaver, B A; Stull, J T et al. (1995) Myosin light chain kinase phosphorylation in swine carotid artery contraction and relaxation. Am J Physiol 268:H2466-75
Rembold, C M; Van Riper, D A; Chen, X L (1995) Focal [Ca2+]i increases detected by aequorin but not by fura-2 in histamine- and caffeine-stimulated swine carotid artery. J Physiol 488 ( Pt 3):549-64
Chen, X L; Rembold, C M (1995) pHi, [Ca2+]i, and myosin phosphorylation in histamine- and NH4(+)-induced swine carotid artery contraction. Hypertension 25:482-9
Chen, X L; Rembold, C M (1995) Phenylephrine contracts rat tail artery by one electromechanical and three pharmacomechanical mechanisms. Am J Physiol 268:H74-81

Showing the most recent 10 out of 32 publications