| 1. |
- Arner, Anders, et al.
(författare)
-
Activation of contraction and ATPase activity in intact and chemically skinned smooth muscle of rat portal vein. Dependence on Ca++ and muscle length
- 1983
-
Ingår i: Circulation Research. - 0009-7330. ; 53:5, s. 695-702
-
Tidskriftsartikel (refereegranskat)abstract
- The mechanical manifestations of muscle contraction (force development or shortening) are accompanied by an increased turnover of chemical energy (ATPase activity, JATP). In intact rat portal veins activated by high potassium medium to produce graded contractions at different levels of extracellular calcium, a linear dependence of oxygen consumption on force was found. The slope of the relation (metabolic tension cost) was higher during early stages than during late stages of contraction, possibly reflecting a transient high crossbridge ATP turnover rate. Chemically skinned (Triton X-100) rat portal vein preparations were used to study the energy turnover of the smooth muscle contractile system under constant activation. In these preparations, JATP increased on activation by calcium in the presence of 1 microM calmodulin, remained constant for maintained contractures, and decreased promptly on relaxation. Force declined with each repeated contraction at optimal calcium level (10(-4.5) M), but the relation between force and JATP remained invariant and agreed with that of the intact muscle during the transient of high ATP turnover. Calcium activation in the range 10(-9) to 10(-4.5) M caused a progressively steeper (nonlinear) increase in JATP with force. Length-force relations showed a lower relative force at muscle lengths below L0 in the intact than in the skinned tissue, possibly indicating depression of excitation-contraction coupling. The slope of the relation between JATP and force was lower when length was varied than when calcium was varied. At a length where no external force was produced, the activated muscle had a significantly higher JATP than while relaxed (10(-9) M Ca++). Together with previous results showing calcium dependence of the force-velocity relation, the present study indicates an influence of calcium on crossbridge kinetics in smooth muscle.
|
|
| 2. |
|
|
| 3. |
- Arner, Anders, et al.
(författare)
-
Energy turnover and mechanical properties of resting and contracting aortas and portal veins from normotensive and spontaneously hypertensive rats
- 1981
-
Ingår i: Circulation Research. - 0009-7330. ; 48:4, s. 539-548
-
Tidskriftsartikel (refereegranskat)abstract
- Aortas and portal veins from spontaneously hypertensive rats (SHR) and matched normotensive Wistar-Kyoto rats (WKY) were studied with respect to their energy turnover and mechanical properties. Relaxed aortas fom SHR 16--17 weeks and 20--25 weeks of age were stiffer, had smaller circumference, and greater maximal active wall tension compared to WKY aortas. Active stress (forced/areas) was not different. Passive and active length-force relations of portal veins from 16 to 17-week-old SHR and WKY were not different. O2 consumption (JO2) and lactate production (JLA) were studied in aortas and portal veins from 20- to 25-week-old rats. In relaxed aortas, JO2 was 0.63 +/- 0.03 (n = 1) and 0.54 +/- 0.03 (n = 10) mu mol/min per g dry wt in SHR and WKY, respectively (P less than 0.05). On activation by high-K+ solution, JO2 increased with tension in a similar way in both groups. In contrast, JLA, about 0.85 mu mol/min per g, did not differ, and decreased with tension development. JO2 of relaxed portal veins, about 1.5 mu mol/min per g dry wt, and the increase in JO2 with contraction were not different between SHR and WKY, but the JO2-active stress relation was steeper in spontaneous activity than in Kv+ contractures. JLA was similar in SHR and WKY portal veins, about 1 mu mol/min per g, and unlike behavior of the aortas, it increased with tension. Thus it is evident that SHR show increased arterial metabolism, which is not accounted for by an increased energy demand of the contractile system.
|
|
| 4. |
- Arner, Anders, et al.
(författare)
-
Structural and mechanical adaptations in rat aorta in response to sustained changes in arterial pressure
- 1984
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 122:2, s. 119-126
-
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).
|
|
| 5. |
|
|
