PHARMACOLOGY OF CORONARY ARTERY CALCIUM CHANNELS

Project: Research project

Description

The long-term objective of this project is to understand how potassium(K)
decolorization, endothelin (EN), and nifedipine (NIF) regulate coronary
artery smooth muscle cell(SMC) free calcium (Ca1). More specifically, how
might NIF attenuate K and EN-induced increase in Ca? The overall
hypothesis is that EN potentiates K depolarization-induced activation of
voltage-gated Ca channels (VGCC), thereby increasing Ca1; NIF is postulated
to inhibit these processes by high affinity binding to the VGCC. However,
EN also releases Ca from the sarcoplasmic reticulum (SR) and, thus
increases Ca without depolarization of SMC. Other than elevated external
K, no vasoconstrictor directly causes depolarization of coronary artery
SMC, which would activate VGCC. Therefore, additional mechanisms,
including interactions between VGCC and the SR, should be determined for
the action of NIF. Methods involve the use of single SMC that are freshly
dispersed from bovine conary artery and can be contracted by EN and K.
Three measures of SMC Ca regulation will be obtained: 1) whole-cell VGCC
currents will be studied with patch-clamp, 2) Ca will be measured with
fura-2 microfluorimetry, and 3) contraction will be verified with video
recording. Experimental design for achieving specific aims basically
involves obtaining these three measures simultaneously during
depolarization, and/or exposure to EN, and/or NIF, this allowing precise
experimental control to differentiate the actions of these agents on VGCC
or the SR. Specific aims are to determine: 1) NIF inhibition of VGCC. The
decrease of VGCC current and Ca caused by NIF is hypothesized to be
directly related to the amount of membrane depolarization during voltage-
clamp. 2) NIF inhibition of SR Ca release/sequestration. The hypothesis to
be tested is the EN-induced Ca release from the SR is inhibited by NIF,
primarily due to the inhibition of VGCC needed to refill the SR with Ca.
3) Potentiation of VGCC by EN. EN is hypothesized to shift the voltage-
dependence for VGCC activation such that increased Ca influx occurs near
the resting membrane potential. 4) NIF inhibition of VGCC that have been
potentiated by EN. The significance of this research is the increased
understanding of the pivotal role of VGCC in the cellular actions of EN and
NIF of the coronary artery.
StatusFinished
Effective start/end date4/1/903/31/95

Funding

  • National Institutes of Health: $119,045.00
  • National Institutes of Health
  • National Institutes of Health: $52,125.00
  • National Institutes of Health: $84,741.00
  • National Institutes of Health: $46,186.00
  • National Institutes of Health
  • National Institutes of Health

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Endothelins
Calcium Channels
Nifedipine
Coronary Vessels
Pharmacology
Sarcoplasmic Reticulum
Smooth Muscle Myocytes
Cytophotometry
Video Recording
Vasoconstrictor Agents
Membrane Potentials
Potassium
Research Design
Arteries
Calcium

ASJC

  • Medicine(all)