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- Arner, Anders, et al.
(författare)
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Structural and mechanical adaptations in rat aorta in response to sustained changes in arterial pressure
- 1984
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 122:2, s. 119-126
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Tidskriftsartikel (refereegranskat)abstract
- Structural and mechanical adaptations in response to sustained changes in arterial pressure were studied on abdominal aorta of the male rat. Two models were used: 1. Aortic ligature (L), immediately below the renal arteries producing hypotension distal to the knot (duration before sacrifice 6 weeks or 3 months). 2. One-clip renal hypertensive rats (H) (duration 6 weeks). Normotensive sham-operated rats (C) served as controls. At sacrifice mean tail artery pressure was L: 58 +/- 1, C: 110 +/- 3, and H: 163 +/- 5 mmHg (SE, N=6). Segments of abdominal aorta were mounted in vitro for determination of their length-tension relations (activation: High-K+ solution with 2.5 mM Ca2+). At end of experiments the vessels were supramaximally stimulated at optimal circumference (1o) for active force (activation: High-K+ solution with 10 mM Ca2+, and 10(-5) M noradrenaline), and then fixated for light and electron microscopy. Passive and active length-tension relations were shifted towards lower and higher circumference values for hypo- and hypertensive vessels, respectively. The 1o values were L: 3.60 +/- 0.13, C: 4.44 +/- 0.19, and H: 4.91 +/- 0.29 mm. The media thickness at 1o was reduced in L: 56.0 +/- 3.3, and increased in H: 81.3 +/- 2.4 compared to C: 73.4 +/- 1.8 micron. Maximal active wall stress was L: 46.6 +/- 9.8, C: 74.2 +/- 7.0, and H: 83.8 +/- 7.7 mN/mm2. Intracellular volume (ICV) in the media was L: 30 +/- 2, C: 45 +/- 3, and H: 44 +/- 1% (n=4 for each).
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| 2. |
- Uvelius, Bengt, et al.
(författare)
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Effects of phasic and tonic activation on contraction dynamics in smooth muscle
- 1980
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 109:4, s. 399-406
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Tidskriftsartikel (refereegranskat)abstract
- Responses to isotonic quick releases of rabbit urinary bladder strips and rat portal veins activated by AC-stimulation and K+-high medium were studied. The AC stimulation was adjusted to give the same tension as th K+-contractures. Releases were performed at peak of the contractions (which was attained after 1.5-4.5 s AC-stimulation or 2-3 min in K+-high solution). The length response consisted of 3 parts: (1) elastic recoil, (2) isotonic transient, (3) steady shortening. Shortening velocity was determined at 100 ms after the release, as phase (2) had subsided by then. Characteristics of the initial elastic response was virtually unaffected by the mode of stimulation for both preparations. Vmax was significantly higher for the AC-stimulations than for the K+-contractures (bladder: 0.37 l/s vs. 0.26 l/s, portal vein: 0.46 l/s vs. 0.33 l/s). By means of computer analysis a fast exponential shortening component comprising the larger part of phase (2) could be separated from the subsequent slower shortening (see further in Hellstrand & Johansson 1979). In each preparation the amplitude of this exponential was the same for both modes of activation. The time constant was, however, smaller for the AC-stimulation preparations. Our results thus indicate that in response to a sudden decrease in force the initial elastic recoil is the same whereas the rate of transition to steady shortening, and the steady shortening velocity itself, are lower for preparations activated by K+-high medium compared to AC-stimulation.
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