Osmotically inactive skin Na+ storage in rats

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Item Type:	Article
Title:	Osmotically inactive skin Na+ storage in rats
Creators Name:	Titze, J., Lang, R., Ilies, C., Schwind, K.H., Kirsch, K.A., Dietsch, P., Luft, F.C. and Hilgers, K.F.
Abstract:	Compared with age-matched men, women are resistant to the hypertensive effects of dietary NaCl; however, after menopause, the incidence of salt-sensitive hypertension is similar in women and men. We recently suggested that osmotically inactive Na+ storage contributes to the development of salt-sensitive hypertension. The connective tissues, including those immediately below the skin that may serve as a reservoir for osmotically inactive Na+ storage, are affected by menopause. We tested the hypothesis that ovariectomy (OVX) might reduce osmotically inactive Na+ storage capacity in the body, particularly in the skin. Male, female-fertile, and female OVX Sprague-Dawley (SD) rats were fed a high (8%)- or low (0.1%)-NaCl diet. The groups received the diet for 4 or 8 wk. At the end of the experiment, subgroups received 0.9% saline infusion and urinary Na+ and K+ excretion was measured. Wet and dry weight (DW), water content in the body and skin, total body Na+ (rTBNa+) and skin Na+ (rSKNa+) content were measured relative to DW by desiccation and dry ashing. There were no gender differences in osmotically inactive Na+ storage in SD rats. All SD rats accumulated Na+ if fed 8% NaCl, but rTBNa+ was lower in OVX rats than in fertile rats on a low (P < 0.001)- and a high (P < 0.05)-salt diet. OVX decreased rSKNa+ (P < 0.01) in the rats. A high-salt diet led to Na+ accumulation (ΔSKNa+) in the skin in all SD rats. Osmotically inactive skin Na+ accumulation was ∼66% of {delta}SKNa+ in female and 82% in male-fertile rats, but there was no osmotically inactive Na+ accumulation in OVX rats fed 8% NaCl. We conclude that skin is an osmotically inactive Na+ reservoir that accumulates Na+ when dietary NaCl is excessive. OVX leads to an acquired reduction of osmotically inactive Na+ storage in SD rats that predisposes the rats to volume excess despite a reduced Na+ content relative to body weight.
Keywords:	Blood Pressure, Body Weight, Bone and Bones, Inbred Dahl Rats, Menopause, Minerals, Natriuresis, Ovariectomy, Sex Characteristics, Skin, Sodium, Sodium Chloride, Sprague-Dawley Rats, Water, Water-Electrolyte Balance, Animals, Rats
Source:	American Journal of Physiology Renal Physiology
ISSN:	0363-6127
Publisher:	American Physiological Society
Volume:	285
Number:	6
Page Range:	F1108-F1117
Date:	December 2003
Official Publication:	https://doi.org/10.1152/ajprenal.00200.2003
PubMed:	View item in PubMed

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