Differences between sheep excreting sodium predominantly in their urine or in their faeces: the effect of changes in sodium intake

Michell, A.R.; Moss, Peter

doi:10.1113/expphysiol.1992.sp003646

Cited by 9 publications

(11 citation statements)

References 17 publications

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“…The U sheep excreted 41 % of their sodium in faeces, whereas F sheep excreted 69 % in faeces (compared with 38 and 86 % when these sheep were tested previously; Michell & Moss, 1992b). As before, the U slheep had a higher water turnover, with both water intake and urine output significantly exceeding those of F sheep (P < 0 05; Table 1).…”

Section: Resultssupporting

confidence: 56%

“…Two groups of six Scottish Blackface ewes, which had already been classified as U or F excretors of sodium (Michell & Moss, 1992b), were re-accustomed to metabolism cages and diets of specified sodium contcnt. The basal diet comprised 0 5 kg oats, 0-3 kg straw, 0.2 kg bran and a mineral-vitamin supplement (31 g).…”

Section: Methodsmentioning

confidence: 99%

“…Diets and excreta were measured and analysed as before (Michell & Moss, 1992b) and 20 ml jugular venous samples were collected before feeding on the 2 days preceding dehydration and after 48 and 72 h of dehydration. Samples were taken into chilled heparinized syringes and immediately centrifuged in the cold.…”

Section: Methodsmentioning

confidence: 99%

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Responses to reduced water intake, including dehydration natriuresis, in sheep excreting sodium predominantly in urine or in faeces

Michell

Moss²

1995

Experimental Physiology

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SUMMARYSheep which were predominantly urinary excretors (U) or faecal excretors (F) of sodium were exposed to a 75% reduction of water intake for 72 h. The experiment was performed on moderate, low or high sodium intakes (0-4, 0-05 or 1-2 mmol kg-' day-') to test the hypothesis that dehydration natriuresis was not a cause of sodium depletion but a defence against hypernatraemia. Dehydration caused elevation of plasma sodium concentration, osmolality, antidiuretic hormone (ADH) and oxytocin but, as in other experiments, a fall in haematocrit. The two higher levels of sodium intake were associated with dehydration natriuresis but also a smaller increase in faecal sodium excretion in both U and F sheep. On low sodium intake, however, neither urinary nor faecal sodium excretion increased in either group of sheep although the rise in plasma sodium concentration caused by dehydration was similar. Thus, when there is a risk of sodium depletion, due to low sodium intake, dehydration natriuresis does not occur, consistent with the hypothesis. Active sodium transport inhibitor (ASTI) and atrial natriuretic peptide (ANP) fell rather than rose during dehydration. Since aldosterone is suppressed by the higher levels of sodium intake, none of these hormones is likely to mediate dehydration natriuresis in sheep. F sheep showed more effective renal and faecal water conservation when dehydrated. During water restriction, the urinary potassium excretion of U sheep was significantly reduced, unlike that of F sheep; moreover, the latter maintained an identical plasma potassium concentration between baseline and restriction period, whereas in U sheep it was 0-3 mmol l`higher during water restriction. Increased drinking rather than reduced urine output was the basis of rehydration when ad lib. water intake was restored.

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Section: Resultssupporting

confidence: 56%

Section: Methodsmentioning

confidence: 99%

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Responses to reduced water intake, including dehydration natriuresis, in sheep excreting sodium predominantly in urine or in faeces

Michell

Moss²

1995

Experimental Physiology

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“…Interestingly, urine osmolality increased with aging in the basal state and yet urine sodium decreased. While the reasons are not fully understood, studies in sheep showed that sometimes daily sodium output is regulated in these animals by increasing fecal sodium excretion with a greater increase in urinary potassium with phosphate and urea excretion also suggested to be greater (21). Therefore, it is possible that the increase in urine osmolality with a lower sodium excretion in our study reflects an increase in other ions and electrolytes.…”

Section: Discussionmentioning

confidence: 46%

Urine-concentrating defects exacerbate with age in male offspring with a low-nephron endowment

Singh

Denton

Bertram³

et al. 2011

American Journal of Physiology-Renal Physiology

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“…However, given the degree of disparity in sodium excretion between the groups, which one would predict would cause marked increases in extracellular fluid volume and arterial pressure, it is unlikely to simply reflect sodium retention. It is possible that reabsorption via the gut is altered or influenced by circadian rhythm in the uni-x animals (37), more sodium is being sequestered in the sheep rumen, or fecal sodium excretion (19) is greater in the uni-x animals. It is also possible that the diurnal regulation of renal function is altered in the uni-x animals.…”

Section: Discussionmentioning

confidence: 98%

Renal responses to furosemide are significantly attenuated in male sheep at 6 months of age following fetal uninephrectomy

Singh

Bertram²,

Denton

2012

American Journal of Physiology-Regulatory, Integrative and Comp

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We have previously shown that fetal uninephrectomy (uni-x) at 100 days of gestation (term = 150 days) in male sheep results in a 30% nephron deficit, reduction in glomerular filtration rate (GFR) and renal blood flow, and elevation in arterial pressure at 6 mo of age. Furthermore, in response to an acute 0.9% saline load, sodium excretion was significantly delayed in uni-x animals leading us to speculate that tubuloglomerular feedback (TGF) activity was reset in uni-x animals. In the present study, we induced TGF blockade by furosemide administration (1.5 mg/kg iv over 90 min) and determined GFR, effective renal plasma flow, and urine and sodium excretion responses in 6-mo-old male sheep. In response to furosemide, a significant diuresis and natriuresis was observed in the sham group; however, the response was significantly delayed and reduced in uni-x animals (both, P(treatment×time) < 0.001). Cummulative urinary and sodium output was significantly less in the uni-x compared with the sham sheep (both, P(treatment×time) < 0.001). GFR was increased in the sham but not the uni-x sheep (P(treatment×time) < 0.0001). In conclusion, the excretory response to furosemide was attenuated in the uni-x sheep, and this suggests a rightward resetting of the TGF operating point. The TGF mechanism is important in the fine tuning of sodium homeostasis and is likely a contributing factor for the dysfunction in sodium regulation we have previously observed in the uni-x animals.

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Differences between sheep excreting sodium predominantly in their urine or in their faeces: the effect of changes in sodium intake

Cited by 9 publications

References 17 publications

Responses to reduced water intake, including dehydration natriuresis, in sheep excreting sodium predominantly in urine or in faeces

Responses to reduced water intake, including dehydration natriuresis, in sheep excreting sodium predominantly in urine or in faeces

Urine-concentrating defects exacerbate with age in male offspring with a low-nephron endowment

Renal responses to furosemide are significantly attenuated in male sheep at 6 months of age following fetal uninephrectomy

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