Renal vasoconstrictor responses to static exercise during orthostatic stress in humans: effects of the muscle mechano‐ and the baroreflexes

Momen, Afsana; Thomas, Karen; Blaha, Cheryl; Gahremanpour, Amir; Mansoor, Ather; Leuenberger, Urs A.; Sinoway, Lawrence I.

doi:10.1113/jphysiol.2005.104612

Cited by 16 publications

(14 citation statements)

References 29 publications

(36 reference statements)

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“…Previous reports showed that LBNP > ¡20 mmHg unloads both low and high pressure baroreceptors and activates sympathetic system (Jacobsen et al 1993;Khan et al 2002). In addition, other reports (from this laboratory and others) showed increased plasma norepinephrin (Momen et al 2006) and increased renal norepinephrin outXow during LBNP > ¡20 mmHg (Tidgren et al 1990). Thus, it is considered Fig.…”

Section: Renal Blood Xow Velocity and Renal Vascular Resistancementioning

confidence: 80%

“…One subject was excluded from the analysis of this protocol because it was not possible to get blood pressure recordings of good quality from the Wnger. According to previous studies from this laboratory during the IFHG there is a sympathetically mediated renal vasoconstriction mainly due to stimulation of the sensory Wbers within the exercising muscle (Momen et al 2003(Momen et al , 2006.…”

Section: Protocol a Isometric Fatiguing Handgrip (Ifhg)mentioning

confidence: 95%

“…In a series of studies from our laboratory, it was found that isometric fatiguing handgrip (IFHG) elicited renal vasoconstriction mediated through SNS activation (Momen et al 2005(Momen et al , 2003. In a subsequent study, renal vasoconstriction was elicited during lower body negative pressure (LBNP) protocol with no signiWcant change in blood pressure (BP) (Momen et al 2006). LBNP simulates orthostatic stress, deactivates baroreceptors and causes SNS activation and renal vasoconstriction (Baily and Sinoway 1990).…”

Section: Introductionmentioning

confidence: 98%

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Changes of elastic properties of central arteries during acute static exercise and lower body negative pressure

et al. 2007

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The aim of this investigation was to determine the acute effects of isometric fatiguing handgrip (IFHG) and lower body negative pressure (LBNP) on indices of central arterial stiffness. Thirteen subjects were studied. Renal blood velocity (Duplex Ultrasound) and blood pressure (Finapres) were monitored during IFHG and LBNP at -30 and -50 mmHg. Radial pulse-wave forms were recorded by applanation tonometry. Central aortic waveforms and other hemodynamic parameters were assessed using the Sphygmocor software. Renal vascular resistance index (RVRI; mean BP/renal blood velocity) was used as index of sympathetic nervous system (SNS) engagement. RVRI increased during both IFHG and LBNP indicating that SNS was engaged; however, BP increased only during the IFHG. Pulse-wave analysis showed that during the IFHG protocol the transit time of the pulse wave decreased and the peripheral pulse pressure/nonaugmented central pulse pressure ratio increased from baseline. Both of these measurements suggest an increase in central large artery stiffness. During LBNP no changes in the indices of central stiffness were noted, in spite of a similar level of sympathetic system engagement. Heart rate increased during both protocols, whereas augmentation index increased during the IFHG protocol and decreased during the LBNP. Our major conclusion was that blood pressure rather than sympathetic activity seems to play the major role in modulating the elastic properties of the central arteries. The decrease in augmentation index during the LBNP protocol can be attributed to the increased heart rate, given that there is a negative correlation between these two parameters.

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Section: Renal Blood Xow Velocity and Renal Vascular Resistancementioning

confidence: 80%

Section: Protocol a Isometric Fatiguing Handgrip (Ifhg)mentioning

confidence: 95%

Section: Introductionmentioning

confidence: 98%

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Changes of elastic properties of central arteries during acute static exercise and lower body negative pressure

et al. 2007

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“…The rapid sympathetic nerve responses are hardly explained by the muscle mechanoreflex. Momen et al (31,32) recently reported that a 15-s bout of evoked static muscle contraction by percutaneous electrical stimulation increased renal vascular resistance in humans, suggesting that muscle mechanoreflex engagement was responsible for the increase in renal vascular resistance. Taken together, the muscle mechanoreflex may not work on the whole vascular system but may affect the renal vascular bed particularly.…”

Section: Central Command But Not the Muscle Mechanoreflex Is Responmentioning

confidence: 99%

Gadolinium does not blunt the cardiovascular responses at the onset of voluntary static exercise in cats: a predominant role of central command

Matsukawa¹,

Nakamoto²,

Inomoto³

2007

American Journal of Physiology-Heart and Circulatory Physiology

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The cardiovascular adaptation at the onset of voluntary static exercise is controlled by the autonomic nervous system. Two neural mechanisms are responsible for the cardiovascular adaptation: one is central command descending from higher brain centers, and the other is a muscle mechanosensitive reflex from activation of mechanoreceptors in the contracting muscles. To examine which mechanism played a major role in producing the initial cardiovascular adaptation during static exercise, we studied the effect of intravenous administration of gadolinium (55 mol/kg), a blocker of stretch-activated ion channels, on the increases in heart rate (HR) and mean arterial blood pressure (MAP) at the onset of voluntary static exercise (pressing a bar with a forelimb) in conscious cats. HR increased by 31 Ϯ 5 beats/min and MAP increased by 15 Ϯ 1 mmHg at the onset of voluntary static exercise. Gadolinium affected neither the baseline values nor the initial increases of HR and MAP at the onset of exercise, although the peak force applied to the bar tended to decrease to 65% of the control value before gadolinium. Furthermore, we examined the effect of gadolinium on the reflex responses in HR and MAP (18 Ϯ 7 beats/min and 30 Ϯ 6 mmHg, respectively) during passive mechanical stretch of a forelimb or hindlimb in anesthetized cats. Gadolinium significantly blunted the passive stretch-induced increases in HR and MAP, suggesting that gadolinium blocks the stretch-activated ion channels and thereby attenuates the reflex cardiovascular responses to passive mechanical stretch of a limb. We conclude that the initial cardiovascular adaptation at the onset of voluntary static exercise is predominantly induced by feedforward control of central command descending from higher brain centers but not by a muscle mechanoreflex. muscle mechanosensitive receptors; stretch-activated ion channels; mechanical stretch of skeletal muscle; exercise pressor reflex; conscious cats

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“…Several integrative physiology studies have shown that some vascular beds vasoconstrict and some vasodilate in responses to different stressors. [20][21][22] Following salt loading, if vasodilatation in visceral vasculature is sufficient to maintain BP homeostasis, cutaneous vasodilatation should be unnecessary and any decrease in Tre would be minimal. However, our results suggest that vasodilation did occur in the cutaneous vasculature.…”

Section: Between Groups (Independent T-test)mentioning

confidence: 99%

Effect of acute salt ingestion upon core temperature in healthy men

et al. 2011

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Salt intake may cause conflict for the cardiovascular system as it attempts to simultaneously maintain blood pressure (BP) and temperature homeostasis. Our objective was to determine the effect of a salt and water load vs. a water load upon rectal temperature (Tre) in healthy volunteers. Twenty-two healthy, non-hypertensive Caucasian men enrolled in two trials in which they ingested either salt and body temperature water (SALT), or body temperature water (WATER). BP, Tre, cardiac index, peripheral resistance and urine output were monitored one, 2 and 3 h post-baseline. Changes in the dependent variables were compared between those subjects who were salt sensitive (SS) and those who were salt resistant (SR) at the same time intervals. The percentage change reduction in Tre was greater following SALT compared with WATER at +120 min (À1.1±0.7 vs. À0.6 ± 0.5%, P¼0.009) and at +180 min (À1.3 ± 0.8 vs. À0.7 ± 0.6%, P¼0.003). The percentage change reduction in Tre was greater in the SR group compared with the SS group at +180 min (À1.6 ± 0.9 vs. À0.9 ± 0.5%, P¼0.043). SALT decreased Tre more than WATER. SS individuals maintained temperature homeostasis more effectively than SR individuals following SALT. These results may explain why some individuals are SS while others are SR. If these results are generalizable, it would be possible to account for the role of sodium chloride in the development of SS hypertension.

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Renal vasoconstrictor responses to static exercise during orthostatic stress in humans: effects of the muscle mechano‐ and the baroreflexes

Cited by 16 publications

References 29 publications

Changes of elastic properties of central arteries during acute static exercise and lower body negative pressure

Changes of elastic properties of central arteries during acute static exercise and lower body negative pressure

Gadolinium does not blunt the cardiovascular responses at the onset of voluntary static exercise in cats: a predominant role of central command

Effect of acute salt ingestion upon core temperature in healthy men

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