The Effects of Hyperosmolarity on Intact and Isolated Vascular Smooth Muscle. Possible Role in Exercise Hyperemia

Mellander, Stefan; Johansson, Bengt W.; Gray, Sarah D.; Jonsson, O.; Lundvall, J.; Ljung, Bengt

doi:10.1159/000157715

Cited by 75 publications

(86 citation statements)

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“…One determinant of the magnitude of the exercise-induced increase in plasma viscosity and hematocrit in forearm venous blood is the extent to which extracellular fluid shifts produce hemoconcentration in nonexercising vascular systems (Lundvall et al, 1972;Mellanders et al, 1967). The current study suggests that the mechanism(s) responsible for maintaining fibrinogen level constant during and after exercise also serves to blunt the increase in plasma viscosity, which would otherwise occur as a consequence of hemoconcentration.…”

Section: Discussionmentioning

confidence: 67%

“…Decreased renal blood flow is a potent stimulus to renin secretion (Ekblom et al, 1968;Laragh and Sealey, 1973), and reduced renal blood flow during strenuous exercise has been confirmed by many workers (Chapman et al, 1948;Grimby, 1965). Alphaadrenergically mediated renal vasoconstriction (Beveglrd and Shepherd, 1967;Grimby, 1965;Rowell, 1971) and fluid shifts in extrarenal vascular beds, which result in plasma volume contraction during acute exercise (Astrand, 1976;Astrand and Saltin, 1964;Clement and Shepherd, 1976;Mellanders et al, 1967), largely account for the fall in renal blood flow. The close correlations between changes in hematocrit and plasma protein concentration and changes in PRA are consistent with the view that exercise-induced intravascular volume contraction is an important factor influencing renin secretion during exercise.…”

Section: Discussionmentioning

confidence: 95%

“…Hemodynamic (BevegArd and Shepherd, 1967;Ekblom and Hermansen, 1968; Ekblom et af., Mellanders et al, 1967;Rowell, 197 1 ), biochemical (Kotchen et al, 197 1 ;Laragh and Sealey, 1973), and hematologic (Astrand and Saltin, 1964 Martin et al, 1977) changes normally develop during endurance training, and these differences have been cited to account for the improved exercise capacity which characterizes physically conditioned subjects (Beveghrd and Shepherd, 1967;Ekblom et d., 1968;Rowell, 197 1). While performance depends on many factors, most studies indicate that it is ultimately limited by the capacity of the cardiovascular system to increase transport of oxygen to active muscles (Astrand, 1976; Hartley et af., 1969;Rowell, Scheuer andTipton, 1977, 1971).…”

Section: Introductionmentioning

confidence: 99%

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Effects of exercise on plasma viscosity in athletes and sedentary normal subjects

Letcher

Pickering

Chien

et al. 1981

Clinical Cardiology

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Summary:To assess the immediate and long-term effects of exercise on factors regulating blood flow, we measured plasma viscosity (qP) and plasma renin activity (PRA) in 17 trained runners and 16 sedentary healthy subjects before and 10 min after graded treadmill exercise. Resting vP was lower in runners primarily because of significantly lower fibrinogen concentration. Compared to nonrunners with similar 24-h urine electrolyte excretion rates, runners were characterized by lower PRA at rest. In view of the overall correlation between heart rate and PRA before exercise, reduced adrenergic tone was probably a major factor contributing to the lower PRA in runners. After exercise, plasma viscosity and PRA exceeded control levels, and were similar in magnitude in runners and sedentary subjects. Changes in plasma viscosity were less than expected from the degree of hemoconcentration, primarily because enhanced fibrinolysis maintained fibrinogen level constant. To the extent that plasma viscosity affects viscous flow resistance, the results suggest that tissue perfusion and oxygen delivery rate at rest are greater in trained runners than in sedentary subjects, but these variables become similar after maximum exertion.

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Section: Discussionmentioning

confidence: 67%

Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Effects of exercise on plasma viscosity in athletes and sedentary normal subjects

Letcher

Pickering

Chien

et al. 1981

Clinical Cardiology

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“…Besides release of potassium from contracting muscle, anoxia (18), phosphate (19), adenine nucleotides (20), and osmolality (21) have been given consideration as mediators or at least participants in the mediation of exercise hyperemia. While our studies were not designed to examine the role of these substances or effects, there has been mounting evidence (22) that potassium release is of critical importance for the necessary rise of muscle blood flow with exercise.…”

Section: Methodsmentioning

confidence: 99%

On the mechanism of rhabdomyolysis in potassium depletion

Knöchel¹,

Schlein²

1972

J. Clin. Invest.

245

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“…Several hypotheses have been proposed as to the mechanisms responsible for the dilatory effect of hyperosmolar solutions, based on experimental results in peripheral vessels or skeletal muscles: (1) tion, 26 ' 29 (3) decreased actomyosin ATPase activity as a consequence of cellular dehydration, 30 (4) changes in the molecular structure of the myofilaments, 26 3h n and (5) alteration of calcium mobilization. 17 However, the precise mechanism for the dilatory effect is still unclear.…”

Section: Discussionmentioning

confidence: 99%

The effects of hyperosmolar solutions on cerebral arterial smooth muscle.

Sasaki¹,

Kassell²,

Fujiwara³

et al. 1986

Stroke

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HYPEROSMOLAR SOLUTIONS have been used for several purposes; to decrease brain bulk and intracranial pressure, 1 "* to increase drug delivery into the brain for the treatment of malignant brain tumors , 7 or to treat cerebral ischemia.8 "" Intravascular infusion of hyperosmolar solutions has been shown to increase cerebral blood flow (CBF), 12~15 presumably due to a direct vasodilatory effect.14 However, Muizelaar et al 16 have recently demonstrated that intravenous mannitol resulted in constriction of cerebral arteries. Thus, the responses of cerebral arteries to hyperosmolar solutions in vivo are controversial, and little is known about the direct effect of hyperosmolar solutions on isolated cerebral arteries in vitro.Kent et al 17 have recently reported, using rat aortic strips, that hyperosmolar solutions may alter vasoconstriction associated with intracellular calcium mobilization rather than that associated with extracellular calcium influx. However, such a hypothesis may not be applicable to cerebral arteries, since the constrictor responses of cerebral arteries to vasoconstricting agents are mainly dependent on the influx of extracellular calcium.18 " 22The present study was conducted in order to examine the direct effect of hyperosmolar solutions on the constrictor responses of isolated cerebral arteries to several vasoactive agents and to elucidate the mechanisms by which hyperosmolarity might affect the vascular tone. Materials and MethodsAdult mongrel dogs of either sex, weighing 10 to 16 kg, were anesthetized with sodium pentobarbital (30 mg/kg) and sacrificed by exsanguination from the femoral artery.Under magnification, the basilar arteries were dissected from the brain and immediately placed in modified Kreb's bicarbonate solution [(mM): NaCl 120; KC1 4.5; MgSO 4 1.0; NaHCO 3 27.0; KH 2 PO 4 1.0; CaCl 2 2.5; and dextrose 10.0] at 37°C, which was gassed with 95% 0 2 and 5% CO 2 . The pH of the solution ranged from 7.40 to 7.50. The arteries were cut into 4 mm long ring segments and suspended between L-shaped stainless steel holders in organ baths with 10-ml working volumes. Resting tension was adjusted to 2.0 g. The preparations were allowed to equilibrate for 60 minutes before use. Contractile force was recorded isometrically using a Grass FT.03 force-displacement transducer. The transducer signal was then amplified and displayed on a Gould 260 multichannel recorder. In order to check the contractile activity of each specimen, the contractile response to 40 mM KC1 was first obtained on each ring segment. Only specimens which showed a good response to 40 mM K G were used.In the first experiment, the effect of hyperosmolar solutions on the constrictor responses to 40 mM [K + ] o , 10~7M serotonin or 10" 6 M PGF^ was examined. The concentration of each agonist producing approximately 70% of the maximum contraction was used in the present study. The contractile activity of each agonist in the normal Kreb's solution was measured several times until the response became stable. After the response became...

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The Effects of Hyperosmolarity on Intact and Isolated Vascular Smooth Muscle. Possible Role in Exercise Hyperemia

Cited by 75 publications

References 0 publications

Effects of exercise on plasma viscosity in athletes and sedentary normal subjects

Effects of exercise on plasma viscosity in athletes and sedentary normal subjects

On the mechanism of rhabdomyolysis in potassium depletion

The effects of hyperosmolar solutions on cerebral arterial smooth muscle.

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