Effect Of Dietary Sodium Restriction Research Articles

Dietary sodium intake and age in spontaneously hypertensive rats: Effects on blood pressure and sympathetic activity

Spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were placed on sodium restricted diets (9 and 17 umol/g) or on a regular sodium diet (101 umol/g) at 2, 4, 7, or 10 weeks of age, and continued until 16 weeks of age. Severe sodium restriction (9 umol/g) initiated at 2 or 4 weeks of age prevented hypertension development in SHR and severely retarded growth. Hypertension development was attenuated when 9 umol/g was initiated at 7 weeks of age, and was not affected when started at 10 weeks of age. Mean arterial pressure (MAP) in WKY receiving 9 umol Na/g initiated at 2 and 4 weeks of age was below normal, but was not affected when this diet was given at 7 or 10 weeks of age. Less severe sodium restriction (17 umol Na/g) resulted in a reduction in hypertension development when initiated at 2, 4, and 7 weeks of age, but not at 10 weeks of age. MAP was normal in WKY receiving 17 umol Na/g at all ages of diet initiation. When the 9 or 17 umol Na/g diet were initiated at 2, 4, and 7 weeks of age, the response of blood pressure to hexamethonium administration was blunted in SHR relative to both WKY receiving the same diet, and to control SHR receiving 101 umol Na/g. We conclude that both WKY and SHR require a minimum amount of dietary sodium for normal growth and for the achievement of normal BP in WKY, and hypertension in SHR. This sodium requirement decreases with age. SHR and WKY exhibit similar sensitivities to sodium intake with respect to body weight, but the effects on BP are more pronounced in SHR. The BP lowering effects of dietary sodium restriction may be due to a blunting of the pressor effectiveness of the sympathetic nervous system.

Heterogeneity of blood pressure response to dietary sodium restriction in normotensive adults

To investigate the effect of dietary sodium restriction on blood pressure in healthy, normotensive adults, 82 individuals (36 men, 46 women) participated in a study of restricted sodium intake (⩽ 75 mEq/day) for a period of 12 weeks. For the entire population there was a small but significant ( p < 0.01) decrease in mean arterial pressure during sodium restriction. The change in blood pressure was significantly correlated with age ( r = 0.23, p < 0.05). Division of the population at age 40, showed that the older individuals were more likely to have a decreased blood pressure during sodium restriction, while as a group younger adults showed no change. The individual blood pressure responses were heterogeneous with increases in pressure observed in some subjects. These results suggest that “sodium sensitivity” of blood pressure may be more evident with increasing age. Further, sodium restriction in all normotensive adults may not be innocuous.

Effect of dietary sodium restriction on taste responses to sodium chloride: a longitudinal study

Normotensive adults on low-sodium, weight-loss, and control diets recorded preferences and perceived saltiness for sodium chloride (NaCl) added to cream soup at intervals over 1 yr. Reduction in sodium intake and excretion accompanied a shift in preference toward less salt: preferred concentrations by ad libitum salting declined from 0.72% at the onset to 0.33% NaCl at week 24; hedonic scores for high concentrations of NaCl decreased significantly while scores for low concentrations increased. After 3 mo of sodium restriction, NaCl preferences readjusted to a lower level: ad libitum additions of NaCl were similar after 13, 24, and 52 wk. Less hedonic variation was observed among controls than among Na-restricted groups. The weight-loss group showed increased liking for mid-range NaCl levels. Mechanisms underlying preference changes, including physiological, behavioral, and context effects, may provide insights into maintenance of low-sodium diets for treatment and prevention of hypertension.

Role of sodium in hypertensive cardiac hypertrophy.

Cardiac hypertrophy in systemic hypertension may not result simply from increased afterload. Previous studies indicate that factors other than blood pressure may influence cardiac hypertrophy. We evaluated the effects of dietary sodium restriction in two-kidney one-clip renal hypertensive rats. After the renal artery had been clipped, the rats received a normal diet until hypertension was established; thereafter, a sodium-deficient diet was instituted in one group. Clipped rats on a regular diet had significantly higher systolic blood pressures than sham-operated controls (205 +/- 9 vs. 129 +/- 1 mm Hg, respectively). Sodium restriction did not reverse hypertension (190 +/- 8 mm Hg), but led to a significant reduction of relative heart weight compared to rats on the normal diet (2.94 +/- 0.24 vs. 3.86 +/- 0.23 mg/g, respectively; P less than 0.01). The hypertrophied hearts of animals on the regular diet showed depressed tissue catecholamines (significant only for norepinephrine); sodium restriction resulted in a restoration to normal levels. Thus, we demonstrated a dissociation of blood pressure and cardiac hypertrophy in the two-kidney one-clip model, similar to previous findings in other models. Our results support the concept that factors other than blood pressure contribute to cardiac hypertrophy. Dietary sodium intake appears to be one such factor. In addition, a possible role of the sympathetic nervous system is suggested.

Effects of dietary sodium restriction on heart rate control in rats.

The effects of dietary sodium restriction on heart rate control were evaluated in male Wistar rats maintained for 4 wk on a low- (22 meq/kg diet) or standard (141 meq/kg diet) sodium diet. In conscious low-sodium rats, atropine produced heart rate increases greater than in standard sodium animals, indicating that basal parasympathetic tone was elevated. Sodium restriction did not affect basal sympathetic tone, since similar reductions in heart rate were produced by propranolol in both dietary groups. However, sympathetically mediated tachycardic responses to sodium nitroprusside were augmented in low-sodium rats. This enhancement of sympathetic function was also observed in low-sodium animals after pithing. The increases in heart rate produced by spinal sympathetic stimulation were significantly accentuated; whereas, responses to norepinephrine were not affected by the diets. This finding is in agreement with the observation that the chronotropic responses elicited by isoproterenol in isolated atria were not altered. When neuronal influences on heart rate were blocked by combined administration of atropine and propranolol or chlorisondamine in conscious rats, the underlying intrinsic cardiac rate was found to be significantly higher in low-sodium rats. In summary, the present study identifies three effects of sodium restriction on heart rate control in the rat: 1) basal parasympathetic tone is increased, 2) heart rate responses to sympathetic activation are enhanced, and 3) the intrinsic cardiac rate is elevated.

The effect of sodium restriction during gestation on offspring brain development in rats

AbstractSodium restrictive diets are today often recommended to women experiencing the normal edema of pregnancy. This study explores some effects of dietary sodium restriction, imposed during pregnancy, on reproductive performance and brain development in resultant offspring. Pregnant Sprague-Dawley rats were fed diets containing either 0.173, 0.067, 0.040, or 0.022% sodium throughout gestation. All other nutrients in the diet were fed at levels in excess of NAS-NRC requirements. At parturition, litters were trimmed to four offspring and mothers fed Purina Rat Chow throughout lactation. Twenty-one days postpartum, offspring were killed and analyses of selected parameters of brain composition made. Rats fed the 0.040 and 0.022% sodium-containing diets during pregnancy consumed less feed, gained less weight, and exhibited altered fluid consumption patterns compared to rats ingesting the 0.173% sodium control diet. Mothers fed the two diets containing the lowest levels of sodium also had smaller litters, fewer live births, and more stillbirths per litter than control mothers. Birth weights and the number of offspring surviving the lactation period were less in the 0.040 and 0.022% sodium treatment groups. No offspring in the 0.022% sodium diet group survived the lactation period. Brain wet weight, dry weight, cholesterol, protein, and RNA content were decreased in offspring in the 0.040% sodium diet group.

The effects of dietary sodium restriction and potassium supplementation and hypophysectomy on adrenocortical function in the rat

Abstract Aldosterone and corticosterone were measured in incubations of isolated zona glomerulosa cells prepared from the following groups of rats: control; sodium deficient; potassium supplemented; sodium deficient-potassium supplemented; hypophysectomised. In each case the in vitro effects of potassium ions, angiotensin, ACTH and corticosterone on the secretory responses were examined. Corticosterone synthesis was measured in equivalent zonae fasciculata/reticularis cells incubated with and without ACTH. Aldosterone synthesised by zona glomerulosa cells was increased 200% and 300% by sodium deficient and sodium deficient-potassium supplemented diets respectively. Potassium supplementation and sodium restriction increased the in vitro responsiveness of cells to potassium and ACTH and more corticosterone was converted to aldosterone under these conditions. Corticosterone synthesis was reduced by 55% in untreated zona glomerulosa cells of sodium deficient-potassium supplemented rats. Cells from hypophysectomised rats were more responsive to potassium ions and had a reduced rate of corticosterone synthesis. Changes in corticosterone synthesis in response to in vitro stimulation did not always parallel changes in aldosterone synthesis. The latter observation is considered when describing a model for the intracellular control of aldosterone synthesis. In cells isolated from zonae fasciculata/reticularis of sodium deficient, sodium deficient-potassium supplemented and hypophysectomised rats, corticosterone synthesis was reduced by at least 80%. Hypophysectomy did not affect responsiveness to ACTH although cells of sodium deficient rats were more responsive. Changes in steroidogenic function have been correlated with sodium, potassium and water fluxes in whole animals. The effects of dietary manipulation on zone widths of the adrenal cortex have been studied.

The effects of dietary sodium restriction on fluid and electrolyte metabolism in the chicken ( Gallus domesticus)

1. 1. The effect of chronic dietary sodium restriction, with and without administration of furose-mide, was examined in the domestic fowl ( Gallus domesticus). 2. 2. Food intake was not altered by low sodium diet and/or furosemide treatment but gains in body weight were less in birds maintained on the deficient diet. 3. 3. Little changes were noted in plasma electrolytes. 4. 4. Exchangeable sodium and the volume of extracellular fluid were lowered by sodium deficient diet and/or fuorosemide treatment but plasma volume and hematocrit remained unchanged. 5. 5. The results suggest that chickens can maintain vascular volume better than mammals in response to dietary sodium restriction.

Adrenal steroid secretion in the rabbit: sodium depletion, angiotensin II, and ACTH.

ARTICLESAdrenal steroid secretion in the rabbit: sodium depletion, angiotensin II, and ACTHB Braverman, and JO DavisB Braverman, and JO DavisPublished Online:01 Dec 1973https://doi.org/10.1152/ajplegacy.1973.225.6.1306MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByEffect of Angiotensin II and ACTH on Adrenal Blood Flow in the Male Rat Adrenal Gland In Vivo13 November 2017 | Endocrinology, Vol. 159, No. 1Angiotensin II Dilates Bovine Adrenal Cortical Arterioles: Role of Endothelial Nitric OxideEndocrinology, Vol. 146, No. 8Role of adrenocorticotropic hormone in the development and maintenance of the adrenal cortical vasculature20 May 2003 | Microscopy Research and Technique, Vol. 61, No. 3Intraadrenal Interactions in the Regulation of Adrenocortical SteroidogenesisEndocrine Reviews, Vol. 19, No. 2The Adrenal Renin/Angiotensin SystemSodium and potassium balance of captive meadow voles (Microtus pennsylvanicus) fed laboratory chow and vegetation dietsComparative Biochemistry and Physiology Part A: Physiology, Vol. 106, No. 3Effects of acute stress, (1–24)ACTH administration and changes in superfusion temperature and flow rate on the in vitro secretion of glucocorticosteroids and aldosterone from the mongolian gerbil (Meriones unguiculatus) adrenal glandComparative Biochemistry and Physiology Part A: Physiology, Vol. 82, No. 4Evidence for an enhanced transmembrane sodium (Na+) gradient induced by aldosterone in the incubated rat tail artery.Hypertension, Vol. 4, No. 2Evaluation of the effect of pentobarbitone anaesthesia on the plasma potassium concentration in the rabbit and the dog1 May 1981 | Canadian Journal of Anesthesia/Journal canadien d'anesthésie, Vol. 28, No. 3Anti-Inflammatory Steroids: Mode of Action in Rheumatoid Arthritis and Homograft ReactionKinetics of sodium in rabbit arterial wall: inability of aldosterone to alter extra to intracellular distribution11 April 2014 | Journal of Endocrinological Investigation, Vol. 1, No. 3The effects of dietary sodium restriction and potassium supplementation and hypophysectomy on adrenocortical function in the ratJournal of Steroid Biochemistry, Vol. 9, No. 4Steroidogenesis in the Zones of the Mammalian Adrenal CortexThe Renin-Angiotensin System and Aldosterone Secretion during Sodium Depletion in the RatCirculation Research, Vol. 35, No. 4 More from this issue > Volume 225Issue 6December 1973Pages 1306-1310 Copyright & PermissionsCopyright © 1973 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1973.225.6.1306PubMed4357327History Published online 1 December 1973 Published in print 1 December 1973 Metrics

Sodium intake and vascular smooth muscle responsiveness to norepinephrine and angiotensin in the rabbit.

The effect of dietary sodium restriction on the responses to norepinephrine and angiotensin was assessed in two vascular smooth muscle preparations in the rabbit. Sodium restriction reduced the response to angiotensin of both the limb vessels in vivo and the aorta in vitro. The response to norepinephrine was potentiated by sodium restriction in both preparations. The effects on angiotensin responsiveness did not appear to be related to tachyphylaxis, changes in extracellular electrolyte composition, or nonspecific depression of smooth muscle function. Probably, the change in sodium intake induced a change in the smooth muscle cell membranes which modified the affinity of their receptors for angiotensin and norepinephrine.

Effects of dietary sodium restriction during pregnancy on the histochemistry of the rat zona glomerulosa.

Pregnant rats on two levels of dietary Na (1.1, 28.7 meq/100 g) were studied along with their nonpregnant counterparts. At the end of gestation, adrenals were removed and studied histochemically for the demonstration of G6PD and sudanophilic lipids. Plasma Na and K concentrations and hematocrit values were taken as supporting data to aid in the interpretation of the histochemical findings.

EFFECT OF DIETARY SODIUM RESTRICTION ON ADRENAL CORTICAL RESPONSE TO ACTH.

SummaryIn dogs fed a low sodium diet for 5 days before being hypophysectomized and nephrectomized, ACTH exerts a greater aldosterone-stimulating effect than it does in dogs fed approximately 40 mEq of sodium/day. Longer periods of sodium restriction produce a further increase in this action of ACTH. Seventeen-hydroxycorticoid output in response to various ACTH doses is unaffected.