Renin and heart rate responses to haemorrhage are age dependent in conscious lambs

Smith, Francine G.; Basati, Raghmeet; Şener, Alp; Abu-Amarah, Isam

doi:10.1017/s0958067000020091

Cited by 2 publications

(5 citation statements)

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“…Similarly, in conscious dogs, Nelson & Osborn (1993) showed that RBF but not GFR decreased following 20 % haemorrhage. In the present study, and in our previous experiments (Smith & Abu-Amarah, 1997Smith et al 2000), there was little effect of hypotensive haemorrhage on renal haemodynamics in young lambs. This occurs despite a profound decrease in GFR following 20 % haemorrhage (Fig.…”

Section: Discussionsupporting

confidence: 64%

“…This could result from an increase in vasoconstrictor agents, such as angiotensin II, or from a decrease in vasodilator agents, such as nitric oxide. For example, we have previously demonstrated that the renin-angiotensin system is activated in response to haemorrhage in conscious newborn lambs (Smith & Abu-Amarah, 1998;Smith et al 2000). An increase in circulating angiotensin II (ANG II) levels in response to haemorrhage could result in a decrease in GFR.…”

Section: Discussionmentioning

confidence: 99%

“…The following two experiments were carried out in each animal at intervals of 24-48 h and in random order: 20 % haemorrhage (experiment 1), 0 % haemorrhage (experiment 2). (In previous studies, we have demonstrated that 20 % haemorrhage results in a significant decrease in mean arterial pressure in both intact and denervated lambs: Smith & Abu-Amarah, 1998;Smith et al 2000.) On the day of an experiment, each lamb was removed from the vivarium and placed in a supportive sling in the laboratory environment for an equilibration period of at least 60 min.…”

Section: Methodsmentioning

confidence: 99%

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Renal Sympathetic Nerves do not Modulate Renal Responses to Haemorrhage in Conscious Lambs

Smith

2002

Experimental Physiology

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The present study was designed to investigate the renal responses to hypotensive haemorrhage early in life and the role of renal sympathetic nerves in modulating these renal responses. To this end, experiments were carried out in conscious, chronically instrumented lambs with either intact renal nerves (n = 7, Intact) or bilateral renal denervation performed at the time of surgery (n = 5, Denervated). Parameters of renal function were measured before and after 20% haemorrhage (experiment 1) and 0% haemorrhage (experiment 2), the latter serving as a time control. The two experiments were performed in random order at intervals of 24‐48 h. Within 20 min of hypotensive haemorrhage in intact lambs, glomerular filtration rate decreased by ∼60%; this response was not altered by renal denervation. Since renal plasma flow remained constant after haemorrhage, the filtration fraction also decreased. After 20% haemorrhage, urinary flow rate decreased in intact lambs; this response was also not altered by renal denervation. Excretion rates of Na+ and K+ as well as urinary osmolality and free water clearance were not altered by haemorrhage in either intact or denervated lambs. These data provide the first description of renal responses to haemorrhage early in life. In addition, the present findings provide new information that renal responses to haemorrhage early in life do not appear to be modulated by renal sympathetic nerves.

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Section: Discussionsupporting

confidence: 64%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Renal Sympathetic Nerves do not Modulate Renal Responses to Haemorrhage in Conscious Lambs

Smith

2002

Experimental Physiology

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“…The choice of low and high doses was based upon previous dose–response experiments in conscious lambs in our laboratory 12 as the EC 50 and EC 100 natriuretic and diuretic responses to furosemide, respectively. (We have previously determined that blood volume is similar from 1 to 12 weeks of life in sheep at approximately 75 mL/kg 16 …”

Section: Methodsmentioning

confidence: 99%

“…(We have previously determined that blood volume is similar from 1 to 12 weeks of life in sheep at approximately 75 mL/kg. 16 ) The dose of furosemide was obtained by diluting a stock solution of 10 mg/mL (Furosemide Special; SABEX, Boucherville, QC, Canada) using sterile water for injection; 'vehicle' was an equivalent volume of sterile water for injection. During experiments, urine was collected continuously to allow for measurement of cumulative urinary flow rate.…”

Section: Methodsmentioning

confidence: 99%

Age-dependent cardiovascular, renal and endocrine responses to furosemide in conscious lambs

Thomson

Smith

2004

Clin Exp Pharmacol Physiol

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1. The present study was performed to investigate some of the physiological responses to furosemide during postnatal maturation. 2. In 1- (n = 8) and 6-week old (n = 10) conscious, chronically instrumented lambs at least 3 days after surgery, three experiments were performed at intervals of 24-48 h and in random order. Various parameters of cardiovascular and endocrine function, as well as cumulative urinary flow rates, were measured before and after intravenous injection of 0 mg/kg (experiment one), 0.25 mg/kg (experiment two; low dose) and 5 mg/kg (experiment three; high dose) furosemide. 3. After high-dose furosemide, mean venous pressure decreased and there was a transient increase in mean arterial pressure in lambs aged 6 weeks. At 1 week of age, heart rate increased after high-dose furosemide and renal blood flow decreased. After high-dose furosemide, plasma renin activity increased in both groups of lambs, although the effects were greater in 1-week-old lambs. Plasma levels of arginine vasopressin increased after high-dose furosemide in lambs aged 1 but not 6 weeks. Cumulative urinary flow rate responses to furosemide were similar in 1- and 6-week-old lambs. 4. These data provide new information that cardiovascular and endocrine responses to furosemide are developmentally regulated.

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Renin and heart rate responses to haemorrhage are age dependent in conscious lambs

Cited by 2 publications

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Renal Sympathetic Nerves do not Modulate Renal Responses to Haemorrhage in Conscious Lambs

Renal Sympathetic Nerves do not Modulate Renal Responses to Haemorrhage in Conscious Lambs

Age-dependent cardiovascular, renal and endocrine responses to furosemide in conscious lambs

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