# ACTIVITY REGULATION OF SKELETAL ISOMYOSIN EXPRESSION

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA-IRVINE · 1990 · $203,661

## Abstract

Previous studies have provided some evidence to suggest that the different
types of myosin present in skeletal muscle can be modified enzymatically by
repeated bouts of physical activity.  To date, however, no studies have
been designed to adequately test the hypothesis that the myosin isozyme
pattern of a given muscle can be regulated in accordance with the
functional demands of gaiting speed and of force imposed on it during
repeated conventional exercise (running).  We propose to test this
hypothesis by using a normal animal modeland an overload model in which the
medial gastrocnemius and rectus femoris muscles are surgically isolated to
be primarily responsible for muscle activity involving the hindlimb
musculature.  This intervention will limit the total number of fast-twitcha
nd slow-twitch motor units participating in locomotion, thereby forcing any
potential adaptation to become highly focused.  After 8 weeks of surgical
induced overload, the overloaded animals, along with normal controls, will
be subjected to identicle chronic exercise programs in which the variables
of (1) speed and (2) incline or weight addition to animals will be
selectively changed.  some animals will be instrumented for
electromyographic recordings to monitor the relative activation of the
muscles during locomotion.  At the termination of a given exercise program,
the nuscles will be analyzed for:  (1) contractile and fatigue properties;
(2) Ca++ regulated myofibril ATPase; (3) histochemistry to assess
fiber-typing; (4) citrate synthase activity; and (5) myosin analyses
consisting of ATPase (including alkaline and acid inactivation), light
chain electrophoretic patterns, and native myosin electrophoresis to
identify specific fast and slow isozymes.  With this combination of
exercise models, we should be able to assess how physiological stimuli
alter the genetic expression of skeletal muscle in terms of contractile
function.

## Key facts

- **NIH application ID:** 3155773
- **Project number:** 5R01AR030346-09
- **Recipient organization:** UNIVERSITY OF CALIFORNIA-IRVINE
- **SAM.gov UEI:** MJC5FCYQTPE6
- **Principal Investigator:** Kenneth M. Baldwin
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1990
- **Award amount:** $203,661
- **Award type:** 5
- **Project period:** 1982-07-01 → 1993-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3155773

## Citation

> US National Institutes of Health, RePORTER application 3155773, ACTIVITY REGULATION OF SKELETAL ISOMYOSIN EXPRESSION (5R01AR030346-09). Retrieved via MORVS 2026-10-24 from https://api.morvs.ai/grant/nih/3155773. Licensed CC0.

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