Cesium (Cs) - General Discussion

As an alkaline mineral, cesium behaves similarly to sodium, potassium and rubidium chemically. Cesium and potassium enter into a solute complex, which participates in ion antagonism, osmosis, permeability regulation and maintenance of the colloidal state in the living cell. The increase in supplemental potassium increases the rate of excretion or loss of cesium.

Cesium chloride is used as part of alternative cancer therapy. Cesium provides high pH therapy for cancer "by entering the cancer cell and producing an alkaline environment. It has been recommended for all types of cancers including sarcomas, bronchiogenic carcinoma and colon cancer.

Biological interest in rubidium and cesium has been stimulated by their close physicochemical relationship to potassium and their presence in living tissues in higher concentrations, relative to those of potassium, than in the terrestrial environment. Over a century ago Ringer observed that rubidium was similar to potassium in its effect on the contractions of isolated frog heart. Relationships between potassium and rubidium, and between cesium and potassium, have been found in a variety of physiological processes. These relationships exist in such diverse actions as their ability to neutralize the toxic action of lithium on fish larvae, or to affect the motility of spermatozoa, the fermentative capacity of yeast, and the utilization of Krebs cycle intermediates by isolated mitochondria. Their extracellular ionic concentrations also influence the resting potential in nerve and muscle preparations and the configuration of electrocardiograms.

The described metabolic interchangeability suggests that rubidium or cesium might have the ability to act as a nutritional substitute for potassium. Rubidium, and to a lesser extent cesium, can replace potassium as a nutrient for the growth of yeast and of sea urchin eggs. This nutritional replaceability can be extended to bacteria, but higher animals are more discriminating. Additions of rubidium or cesium to potassium-deficient diets prevent the occurrence of characteristic lesions in the kidneys and muscles in rats and, for a short period, permit almost normal growth until death inevitably supervenes.

The occurrence of cesium in biological samples has not been extensively studied. However, it has been found that, like rubidium, the cesium content is much higher in erythrocytes than plasma. Cornelis et al found a mean cesium concentration in serum of 0.74 ng/ml, and in red blood cells of 4.82 ng/g. Several other reports have also indicated that the cesium level in serum or plasma is in the range of 0.74 to 1.33 ng/ml. Both Clemente et al. and Hamilton et al. reported that whole blood contains ~5 ng/ml cesium. Like blood, other tissues contain cesium at a level of about one order of magnitude less than rubidium. Vanoeteren et al. found 9.1 ng cesium per gram of homogenized human lung. Wester found a median of 11.4 ng/g in human heart, and the cesium content was reduced in injured tissue of myocardial infarcted heart.

The cesium content of foodstuffs and feeds has not been examined extensively. Some isolated values have appeared, including 0.1-0.3 mcg/g dry fruit kernels, 0.06-0.07 mcg/g dry maple syrup, 0.1-0.3 mcg/g dry nuts except Brazil nuts, which contained 1.3 mcg/g, 9 ng/g fresh orange juice, and 12.1 ng/g fresh banana pulp. Most fruits and vegetables apparently are quite low in cesium. Duke found 3-11 ng cesium per gram dry weight, and Oakes et al. found <1-3.3 ng/g fresh weight, in a limited variety of examined fruits and vegetables. With such low values reported for individual foods, it is not surprising that daily cesium intakes have been reported to be only 13 +or-7 mcg with English total diets, and 15 mcg with Italian diets.