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Updated: Aug 5, 2026
In vitro Measurements of Tracheal Constriction Using Mice
Published on: June 25, 2012
Different ontogeny of rate of force generation and shortening velocity in guinea pig trachealis
1Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA.
Insights
Juveniles exhibit greater airway responsiveness due to airway smooth muscle changes. This study reveals age-related shifts in force production and shortening velocity in guinea pig trachealis, impacting airway function.
Area of Science:
- Physiology
- Respiratory System
- Smooth Muscle Biology
Background:
- Juveniles often show heightened airway responsiveness compared to adults.
- Airway smooth muscle function is a key factor in airway responsiveness.
Purpose of the Study:
- To investigate age-related changes in guinea pig trachealis muscle force production and shortening velocity.
- To correlate these mechanical properties with airway responsiveness in different age groups.
Main Methods:
- Studied force production (P(o)) and shortening velocity (V(o)) in trachealis muscle from 1-week-old, 3-week-old, and adult guinea pigs.
- Utilized electrical stimulation and force-velocity curve analysis.
- Applied a modified Hill's equation to calculate V(o) and internal resistance to shortening (Rsi).
Main Results:
- Maximum active stress (P(o)) showed minimal change with maturation.
- Rate of stress generation increased significantly with age.
- Maximum shortening velocity (V(o)) initially increased then significantly decreased in adults.
- Internal resistance to shortening (Rsi) exhibited an inverse trend to V(o).
Conclusions:
- Age-related changes in force generation and resistance contribute to altered shortening velocity.
- Elevated shortening velocity in juveniles may play a role in airway hyperresponsiveness.
- Findings provide insights into the developmental physiology of airway smooth muscle.
Abstract:
Juveniles of many species, including humans, display greater airway responsiveness than do adults. This may involve changes in airway smooth muscle function. In the present work we studied force production and shortening velocity in trachealis from 1-wk-old (1 wk), 3-wk-old (3 wk), and 3-mo-old (adult) guinea pigs. Strips were electrically stimulated (60 Hz, 18 V) at their optimal length (l(o)) to obtain maximum active stress (P(o)) and rate of stress generation. Then, force-velocity curves were elicited at 2.5 s from the onset of the stimulus. By applying a recently developed modification of Hill's equation for airway smooth muscle, the maximum shortening velocity at zero load (V(o)) and the value alpha. gamma/beta, an index of internal resistance to shortening (Rsi), were calculated (alpha, beta, and gamma are the constants of the equation). P(o) increased little with maturation, whereas the rate of stress generation increased significantly (0.40 +/- 0.03, 0.45 +/- 0.03, 0. 51 +/- 0.03 P(o)/s for 1 wk, 3 wk, and adult animals). V(o) slightly increased early with maturation to decrease significantly later (1. 79 +/- 0.67, 2.45 +/- 0.92, and 0.55 +/- 0.09 l(o)/s for 1 wk, 3 wk, and adult animals), whereas the Rsi showed an opposite trend (14.98 +/- 5.19, 8.99 +/- 3.01, and 32.07 +/- 5.54 mN. mm(-2). l(o)(-1). s for 1 wk, 3 wk, and adult animals). This early increase of force generation in combination with late increase of Rsi may explain the changes of V(o) with age. An elevated V(o) may contribute to the incidence of airway hyperresponsiveness in healthy juveniles.
