Characterization of small intestinal water, sodium, and potassium transport and morphology in the pig.

The suitability of the young pig for studies of intestinal transport was investigated by determination of net water, sodium, and potassium absorption, and morphometry in jejunum and ileum. Active net absorption was seen in both jejunum and ileum. There was no difference in absorption between segments and there was a good correlation between water and electrolyte transport. Heart rate, arterial pressure, and absorption were constant with time. Villus height and width were similar to those of human, but crypt depth was greater, and the ratio of villus height to crypt depth less. The mucosa was partially permeable to polyethylene glycol 4000 and this marker is not suitable for studies of transport in young pigs.     

Excretion of water, sodium, and potassium during the compensatory renal hypertrophy in hypothyroid rats]

Renal compensatory hypertrophy is studied in age matched euthyroid and radiothyroidectomized female rats. 7 days after uninephrectomy, the hypertrophy of the remaining kidney is equally small in both groups. But 60 days after this operation, the hypothyroid animals show only a 12% increase in the wet weight of the remaining kidney whereas the euthyroid controls increase this weight by 21%. The excretion of water, Na and K are determined in the urine excreted in 5 h after a small water load. The results are related to 1 gram of kidney wet weight. These outputs increase in all animals after uninephrectomy. They are significantly higher in the hypothyroid rats than in the euthyroid controls as well before than 60 days after uninephrectomy. The reduction in tubular Na reabsorption found in the hypothyroid rat may account for the impairment of compensatory renal hypertrophy in hypothyroidism.     

Transport,signaling, and homeostasis of potassium and sodium in plants

Potassium(Kt) is an essential macronutrient in plants and a lack of Ktsignificantly reduces the potential for plant growth and development. By contrast, sodium(Nat),while beneficial to some extent, at high concentrations it disturbs and inhibits various physiological processes and plant growth. Due to their chemical similarities, some functions of Kt can be undertaken by Natbut Kthomeostasis is severely affected by salt stress, on the other hand. Recent advances have highlighted the fascinating regulatory mechanisms of Kt and Nattransport and signaling in plants. This review summarizes three major topics:(i) the transport mechanisms of Ktand Natfrom the soil to the shoot and to the cellular compartments;(ii) the mechanisms through which plants sense and respond to Ktand Natavailability; and(iii) the components involved in maintenance of Kt/Nathomeostasis in plants under salt stress.     

Transport,signaling, and homeostasis of potassium and sodium in plants

Potassium （K＋） is an essential macronutrient in plants and a lack of K＋ significantly reduces the potential for plant growth and development. By contrast, sodium （Na＋）, while beneficial to some extent, at high concentrations it disturbs and inhibits various physiological processes and plant growth. Due to their chemical similarities, some functions of K＋ can be undertaken by Na＋ but K＋ homeostasis is severely affected by salt stress, on the other hand. Recent advances have highlighted the fascinating regulatory mechanisms of K＋ and Na＋ transport and signaling in plants. This review summarizes three major topics： （i） the transport mechanisms of K＋ and Na＋ from the soil to the shoot and to the cellular - compartments; （ii） the mechanisms through which plants sense and respond to K＋ and Na＋ availability; and （iii） the components involved in maintenance of K＋/Na＋ homeostasis in plants under salt stress.     

Effects of sodium, potassium and calcium on salt-stressed barley

We grew barley ( Hordeum vulgare L. CM 72) for a 28-day period and sequentially harvested plants every 3 or 4 days. Plants were salt-stressed with either NaCl or KCl (125 m M ) with or without supplemental Ca (10 or 0.4 m M final concentration, respectively). We determined tissue concentrations of Na, Ca, Mg, K. S, P, Fe, Mn, Cu and Zn for each harvest date by inductively coupled plasma spectrometry. Uptake (specific absorption rate) was calculated from the element content and growth rates. Salinity had significant effects on the uptake and concentrations of most elements. Mg and Mn concentrations declined with time. The concentrations of all other elements determined increased over time. Element uptake on a root dry weight basis declined with time. Three variables were significantly affected by salinity and correlated with growth; 1) the Ca concentration, 2) the total sum of the cation concentration (TC), and 3) the Mn concentration of the shoot. Salinity reduced Ca uptake and concentrations. Supplemental Ca increased Ca concentrations and was positively correlated with growth during salt stress. Salinity doubled TC, which was negatively correlated with relative growth rate (RGR). Relative growth rate declined at TC values above 150 m M . Salinity reduced the uptake and concentration of Mn. Manganese concentrations in the shoot were highly correlated with RGR. Relative growth rate declined at Mn concentrations below 50 nmol (g fresh weight)⁻¹.