# CALCIUM AND SODIUM TRANSPORT IN MUSCLE

> **NIH NIH R01** · UNIVERSITY OF MARYLAND BALTIMORE · 1989 · $205,681

## Abstract

The mechanisms involved in the "active" (uphill) extrusion of
calcium from muscle cells, and in the regulation of steady Ca
balance, are incompletely understood.  Many types of cells,
including invertebrate muscle and vertebrate smooth and cardiac
muscle, employ a Ca transport mechanism in which Na ions
exchange for Ca ("Na/Ca exchange").  Thus, the Na
electrochemical gradient may provide at least some of the energy
for Ca extrusion; moreover, Na/Ca exchange may also mediate Ca
entry when Na electrochemical gradient is reduced.  ATP also
plays a role, in part via an effect on the Na/Ca exchange kinetics,
and in part as fuel for a parallel Ca-ATPase driven "Ca pump".
Internally perfused single giant barnacle muscle cells are
employed as a model system to study Ca transport and
metabolism in muscle.  During the forthcoming project period,
characterization of the Na/Ca exchange system in barnacle
muscle should be completed, including direct determination of the
exchange stoichiometry, and the comparative properties of the
forward (Na entry/Ca exit) and reverse (Ca entry/Na exit) modes
of operation of the exchanger as well as the "futile modes"
(Ca/Ca and Na/Na) exchange.  Of particular interest is the role of
internal Ca and Na in the regulation of exchanger turnover.  The
information obtained from this model system will be applied to
the study of Ca transport and metabolism in arterial smooth
muscle (ASM) cells.  Preliminary studies on rings of bovine tail
artery (Progress Report) indicate that Na/Ca exchange plays a
prominent role in the regulation of (Ca2+)i, the intracellular free
Ca concentration, in this tissue.  In the proposed experiments, a
Ca-sensitive fluorescent dye (fura-2) and digital imaging methods
will be used to measure (Ca2+)i in single, dissociated bovine tail
ASM cells.  (Ca2+)i will be measured in resting and activated cells,
and following reduction of Na electrochemical gradient.  The
latter should provide direct information about the Na/Ca
exchange system in these cells.  Patch clamp methods, in
conjunction with the imaging methods, will be used to measure
the ionic currents associated with Na/Ca exchange, and to
determine the factors that regulate Na/Ca exchange in ASM.  The
results of these experiments should provide new information about
the relative importance of Na/Ca exchange and other (parallel)
Ca transport systems in the regulation of (Ca2+)i in these cells.
The results may be applicable to pathophysiological processes
such as those associated with hypertension.

## Key facts

- **NIH application ID:** 3156252
- **Project number:** 5R01AR032276-06
- **Recipient organization:** UNIVERSITY OF MARYLAND BALTIMORE
- **SAM.gov UEI:** Z9CRZKD42ZT1
- **Principal Investigator:** MORDECAI P BLAUSTEIN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1989
- **Award amount:** $205,681
- **Award type:** 5
- **Project period:** 1983-05-01 → 1990-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3156252

## Citation

> US National Institutes of Health, RePORTER application 3156252, CALCIUM AND SODIUM TRANSPORT IN MUSCLE (5R01AR032276-06). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3156252. Licensed CC0.

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