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Age‐related changes in rat colon mechanics
Author(s) -
BUTT W. G.,
WANG M.,
KAUFMAN S. T.,
RYAN J. P.,
COHEN S.
Publication year - 1993
Publication title -
neurogastroenterology and motility
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.489
H-Index - 105
eISSN - 1365-2982
pISSN - 1350-1925
DOI - 10.1111/j.1365-2982.1993.tb00115.x
Subject(s) - isometric exercise , isotonic , contraction (grammar) , chemistry , egta , calcium , circular muscle , muscle contraction , anatomy , smooth muscle , medicine , biophysics , biology , organic chemistry
To determine whether myogenic factors are responsible for slowed colonic transit in senescent rats, maximum shortening velocity (V 0 ), compliance of the series elastic component (SEC), measurements of passive force in calcium‐depleted tissue and peak isometric force (F 0 ) were examined in proximal and distal colonic circular smooth muscle from 6‐ and 30‐monthold Fischer rats (n = 5). After mucosa was removed, measurements were made on strips stimulated with 80 m >m KCl in a 2.5 m >m Ca 2+ Kreb's solution. Muscle strips were quick released at peak isometric force (F 0 ) to afterloads of 60% of F 0 . The changes in muscle length from zero to 40 msec and 1 to 2 sec after release during isotonic contraction were used to calculate the SEC and V 0 as a fraction of total muscle length. Passive force (F p ) was measured in 2.5 m >m Ca 2+ Kreb's solution and in a zero Ca 2+ , 0.1 m >m EGTA solution to determine the contribution of contractile and passive elements to passive force. The results of these studies indicate there is no difference in the V 0 (L 0 /sec) of adult (8.4 ± 1.5) and aged (7.5 ± 2.0) animals (P ± 0.05). Peak force (F 0 ) in the distal colon of the aged rats was greater than adult rats (1.23 ± 0.1 vs 0.85 ± 0.01 kg/cm 2 , P = 0.05). The stiffness of the parallel elastic component and the length‐tension relationship were similar in adult and aged animals. Negligible decreases in F p were observed in zero calcium medium. However, basal contractile tone was elevated in aged animals (P = 0.05). These studies indicate basic differences in aged colonic circular muscle that may contribute to altered bowel transit and function during ageing.