The effect of dietary sodium and potassium intake on potassium secretion and kinetics in rat distal colon.

Abstract

SUMMARY1. Potassium secretion by the distal colon was examined in relation to the secretion of chloride and absorption of sodium and to the epithelial turnover of 86Rb+ (as an analogue of potassium) in vivo in rats fed a standard, a potassium-rich or a sodium-depleted diet.2. An acute intravenous potassium load stimulated potassium secretion two-to threefold. In rats fed the standard diet, sodium secretion was also increased but no significant change in the lumen-to-plasma sodium flux was detected. The potassium and sodium secretions were accompanied by increased chloride secretion which occurred even when the intravenous load contained no chloride. In rats fed the potassium-rich diet, there was a small increase in sodium absorption and a less marked increase of chloride secretion. In the sodium-depleted rats, however, about 70-80% of the increased potassium secretion was balanced by increased sodium absorption.3. The epithelial turnover rate of 86Rb+ in the rats fed the potassium-rich (t1 12-14 min) and the sodium-depleted (tj 11-13 min) diets was faster than that of those of the standard diet (t1 22-27 min). 4. The epithelial potassium content was 304 + 9 nmol (mg dry weight)-' and was not significantly altered despite considerable variations in potassium secretion rate induced by dietary changes and acute potassium loading.5. It is concluded that epithelial potassium turnover rate is increased during chronic states of increased potassium secretion and that the rise in potassium secretion is consistent with increased activity of the basolateral Na+-K+ pump. Whether the increased potassium secretion is associated with chloride secretion or with increased sodium absorption appears to depend on the absence or presence of the amiloride-sensitive sodium pathway in the apical membrane.

Altered Responses of Aortic Smooth Muscle From Sprague‐dawley Rats With Salt‐induced Hypertension

“…The mechanism by which NaCl loading induces hypokalaemia, which could be reversed by potassium supplementation, is not quite clear. A recent report (Edmonds & Willis 1990) suggests a relationship between dietary sodium and potassium secretion in the colon. Weight loss appears to be a common feature of salt-loaded Sprague-Dawley rats.…”

Aldosterone up‐regulates basolateral Na + ‐K + ‐2Cl − cotransporter‐1 to support enhanced large‐conductance K + channel‐mediated K + secretion in rat distal colon

“…Dietary Na + depletion is commonly used to generate experimental hyper‐aldosteronism 27,32,33 . In the past, the effects of experimental hyper‐aldosteronism on kidney and colon electrolyte transport have been mostly characterized in males, but not in female animals.…”

“…Dietary Na + depletion is commonly used to generate experimental hyper-aldosteronism. 27,32,33 In the past, the effects of experimental hyper-aldosteronism on kidney and colon electrolyte transport have been mostly characterized in males, but not in female animals. However, in accordance with current NIH guidelines regarding biological variability related to sex, we examined the effect of dietary Na + depletion on plasma aldosterone levels in both male and female rats.…”

Dietary Na+ depletion up-regulates NKCC1 expression and enhances electrogenic Cl− secretion in rat proximal colon

“…Male Sprague-Dawley rats (126-150 g; Charles River, Wilmington, MA) were housed 2 per cage and maintained in 12-hour light/dark cycles in temperature-controlled housing. Rats were randomly assigned to groups receiving either standard rodent chow or Na + -de cient diet (MP Biomedicals #02960364) for 7 days to induce secondary hyperaldosteronism, as has been described previously (2,10,24,25). All rats were allowed free access to water throughout.…”