Clinical potassium problems

Alterations in serum potassium are common in many diseases. In a series of 390 determinations of serum potassium, the levels found were low in 24 per cent and high in 2.6 per cent. The major causes of low serum potassium are (1) decreased potassium intake due to intravenous feedings which do not contain potassium; (2) increased loss of potassium in the urine due to accelerated tissue breakdown, or renal lesions; (3) loss from the gastrointestinal tract due to diarrhea, or fistulae, and (4) shift between serum and cells, due to metabolic causes, drugs or changes in pH. The major cause of high serum potassium is uremia with renal retention.Clinical symptoms and signs of low body potassium include muscle weakness and paralysis, which may lead to death in respiratory failure if not corrected, tachycardia, gallop rhythm, dilatation of the heart. The electrocardiogram shows inverted, low amplitude, or isoelectric T waves and a prolonged QT interval. Potassium chloride orally, subcutaneously or intravenously is recommended for use in the treatment of potassium deficits. It should not be used in the presence of oliguria or anuria or dehydration. The amounts of potassium necessary to correct deficits vary widely and cannot be predicted from the serum level. Special reference is made to the prevention and therapy of potassium deficits in diabetic acidosis. High serum potassium levels are difficult to correct. Suggested measures are administration of glucose, insulin or calcium, gastric or peritoneal lavage or use of the artificial kidney.     

A clinical approach to common electrolyte problems: 2. Potassium imbalances.

A clinical approach to potassium imbalances is presented. Hypokalemia is rarely due solely to a reduced intake of potassium; instead, it usually results from a potassium flux into the cells or increased loss of the element, at times combined with a decreased intake. The clinician must seek the cause of the intracellular flux or the source of the gastrointestinal or renal loss. The causes of gastrointestinal losses are generally self evident. Renal potassium wasting, though, generally results from increased mineralocorticoid activity, an increased rate of urinary flow or of sodium delivery to the distal nephron, or both, hypomagnesemia or a combination of these factors. Hyperkalemia may be factitious, but usually it is caused by a flux of potassium from the cells or a decrease in the renal loss of potassium, the latter being mediated by a reduction in renal function, mineralocorticoid activity, or the rate of urinary flow or sodium delivery, or both. In both hypokalemia and hyperkalemia, treatment must be guided by the specific clinical circumstances.     

Electrolyte balance in gastrointestinal disease

Even small losses of gastrointestinal secretions when combined with reduced intake of electrolytes may seriously disturb electrolyte balance. Knowledge of the ionic composition of secretions lost is essential in planning therapy. Loss of gastric contents usually results in excessive loss of chloride; in achlorhydria this is not the case. Loss of sodium and potassium may be large in either case and is often underestimated. Small bowel obstruction results in a more balanced loss of electrolyte which may not affect acidbase balance greatly. In diarrhea loss of base predominates, and may result in a large potassium deficit. Steatorrhea due to nontropical sprue results in large fecal losses of sodium, potassium and chloride, in addition to the large calcium and phosphorus loss. In chronic peptic ulcer excessive ingestion of milk and absorbable alkalies may result in hypercalcemia, azotemia and alkalosis, without hypercalciuria. Since renal function is usually adequate in the milder gastrointestinal disturbances, electrolyte and fluid replacement should be started early, and can be guided by generally available laboratory tests, the carbon dioxide combining power and serum chloride levels, provided the predominate ionic loss is known and potassium deficiency remedied. If this is done, development of serious fluid and electrolyte deficits can usually be prevented.     

Evidence for the presence of separate mechanisms regulating potassium and sodium distribution in Ulva lactuca

1. The methods employed in these and preceding (25-27) studies were shown to allow analysis of true cellular sodium and potassium concentrations. 2. The rate of reaccumulation of potassium by potassium-deficient cells is independent of the presence or absence of sodium in the external medium. 3. Phenylurethane (10(-3)M), a photosynthetic and metabolic inhibitor, causes a marked progressive loss of potassium and gain of sodium, both of which changes are completely reversible on transferring the samples to running sea water. 4. Iodoacetate, while not effective in causing potassium and sodium shifts in the light, effects a loss of potassium and a gain of sodium in the light in the presence of phenylurethane. 5. Arsenate (5 x 10(-3)M) completely protects Ulva against the potassium loss usually observed with iodoacetate in the dark while it affords no protection against the sodium influx under the same conditions. Arsenate given after 18 to 20 hours in iodoacetate gives significant protection against potassium loss in the dark, and allows a slight net reaccumulation of potassium in the light. Arsenate in the dark after iodoacetate affords no protection against the sodium uptake caused by iodoacetate in the dark, while in the light under the same conditions sodium is rapidly secreted to the control level within a few hours. This resecretion of sodium is thought to be primarily an effect of light, the presence of arsenate being incidental. 6. The "decoupling agent" 4,6-dinitro-o-cresol causes a marked progressive increase in cellular sodium and a drop in cellular potassium, though the kinetics of these two movements are distinctly different from each other. 7. Pyruvate (50 mg. per cent) given with iodoacetate (2 x 10(-3)M) for 5 hours in the dark completely prevents the sodium increase caused by iodoacetate, while affording less protection against the potassium loss. Phosphoglycerate, on the other hand, offers more protection against potassium loss, and essentially none against the sodium gain. 8. ATP added in small amounts at short intervals to samples maintained in 10(-3)M iodoacetate in the dark affords significant protection against the potassium loss observed in iodoacetate. Cellular sodium is somewhat higher in the ATP-iodoacetate samples than in the iodoacetate samples. 9. In the discussion of the data presented two major points are emphasized: (1) the close correlation between cellular metabolism and normal cation control; (2) two mechanisms must be operative in cation regulation in this organism: one for moving potassium inwards and the other for transporting sodium outwards. These mechanisms are independent of each other.     

Effect of potassium deficiency on carbon dioxide,cation, and phosphate content of muscle,with a note on the carbon dioxide content of human muscle

Albino rats weighing 160 to 175 gm. were fed a complete synthetic diet containing 0.003 per cent potassium and 0.7 per cent sodium for 40 days. Controls were given the same diet plus adequate added potassium. 1. Data from analyses of serum and skeletal muscle showed (a) a fall in serum chloride concentration and an increase in serum carbon dioxide concentration and pH in the potassium-deficient rats; (b) increases of sodium, magnesium, and calcium and a decrease of potassium in the muscle of the potassium-deficient rats; (c) no change of muscle chloride or carbon dioxide concentrations in the potassium-deficient rats. (2) Application of the Wallace-Hastings calculations to these data revealed (a) intracellular pH of the skeletal muscle of the normal rat to be 6.98 +/- 0.08; (b) an increase in serum partial pressure of carbon dioxide (pCO(2)) in potassium deficiency, together with increases in concentrations of [H(2)CO(2)] and [HCO(3) (-)] per kg. extracellular water and [H(2)CO(3)] per kg. cell water; (c) a decrease in values for [CO(2)] and [HCO(3) (-)] per kg. intracellular water; (d) a fall of intracellular pH in potassium deficiency to 6.42 +/- 0.05. (3) Analyses of sacrospinalis muscle from five men undergoing operation for ruptured intervertebral disc showed a mean value of 9.46 +/- 1.31 mM carbon dioxide per kg. blood-free tissue. Some problems of interpretation of data are briefly discussed.     

Amlodipine preserves the glomerular number in spontaneously hypertensive rats

The calcium channel blockers have individual pharmacological and therapeutic properties that may vary, but as a group, they are effective antihypertensive agents in patients with renal disease. Their effects on the kidney may extend beyond BP reduction alone. Fifteen one-year-old male spontaneously hypertensive rats (SHR) were separated in three groups: Initial control group (IC), Final control group (FC, SHR received standard rat chow and fresh water ad libitum during 15 weeks), Amlodipine group (Aml, SHR) received 0.2 mg/kg/day of amlodipine in addition to food and water during 15 weeks. The glomerular number was estimated using the disector method. In the Control group, the BP level increased almost 20 per cent in the first six weeks (from 186 +/- 11 to 223 +/- 16 mmHg, p<0.01) and then BP level increased almost 15 percent until week 15 (from 223 +/- 16 to 258 +/- 20 mmHg, p<0.01). In the same period, the Aml group showed a progressively low BP, reaching a level almost 50 per cent lower in the week 15 than in the week 1 (from 190 +/- 15 to 101+/-8 mmHg, p<0.01). Amlodipine treatment significantly decreased the serum creatinine, more than 12 per cent lower than the FC group (from 70.4 +/- 6.2 to 61.4 +/- 5.2 micromol/L, p<0.05). However, proteinuria was not different when groups were compared. The FC group reached a glomerular number almost 20 percent smaller than the IC and Aml groups (from 35 x 10(3) +/- 7 x 10(3) in IC group, 34 x 10(3) +/- 4 x 10(3) in Aml group to 27 x 10(3) +/- 3 x 10(3) in FC group, p<0.05). A possible protective effect of amlodipine against the loss of glomeruli in SHR is a major additional action of amlodipine in the treatment of hypertension mainly when the renal lesion already exists.     

RESPIRATORY EFFECTS UPON THE VISUAL THRESHOLD

Measurements are reported of the effects of respiratory stresses upon the absolute threshold of peripheral (rod) vision. Since subjects were kept wholly dark adapted and the photochemical system of the rods therefore stationary, the changes recorded may be assumed to have originated more centrally. To this degree the measurements provide a quantitative index of central nervous imbalance. Breathing room air or 32 to 36 per cent oxygen at about double the normal rate causes the visual threshold to fall to approximately half the normal value within 5 to 10 minutes. This change is due primarily to alkalosis induced by the hyperventilation, and can be abolished or reversed by adding carbon dioxide to the inspired mixtures. Normal or rapid breathing of 2 per cent carbon dioxide causes no change in threshold; with 5 per cent carbon dioxide the threshold is approximately doubled. Breathing 10 per cent oxygen at the normal rate also approximately doubles the threshold. This effect is compensated in part by rapid breathing. When 10 per cent oxygen is breathed at twice the normal rate the threshold usually falls at first, then slowly rises to supernormal levels. Due primarily to variations in their breathing patterns subjects yield characteristically different responses on sudden exposure to low oxygen tensions with breathing uncontrolled. The threshold may either rise or fall; and on release from anoxia it may rise, or fall to normal or subnormal levels. The threshold adjusts to anoxia rapidly; exposures lasting 5 to 6 hours do not produce greater or more persistent changes than those of much shorter duration.     

Oxygen consumptions and potassium contents of slices of rat renal cortex.

An oxygen electrode respirometer for determining the oxygen consumption of slices of mammalian renal cortex is described and assessed. Though rat renal cortical slices incubated in potassium-free medium for one hour lost 102 +/- 14 mmol of potassium/kg dry weight, there was only a small, nonsignificant fall in oxygen consumption. In contrast the oxygen consumption of slices incubated in potassium-free medium with 10 mmol.1-1 ouabain was markedly reduced (by 32 +/- 6%), while such slices lost 180 +/- 15 mmol of potassium/kg dry weight. These disproportionate effects on potassium loss and inhibition of oxygen consumption suggest that in renal cortical slices the loss of potassium in low potassium medium is not primarily due to inhibition of the conventional sodium pump.     

The composition of the leachate through cropped and uncropped soils in lysimeters compared with that of the rain

Summary The composition of the leachate from undisturbed monolith lysimeters cropped with white clover or meadow fescue or maintained bare was compared with that of the rain falling on them. No nitrogen fertilizer was applied only an initial dressing of phosphorus and potassium. The grass received much more nitrogen from the rain than it lost by leaching whereas the clover lost more than it received. Most of the leached nitrogen was NO₃-N - 92 per cent on the bare soil and 90 per cent on the clover. About 27lb nitrogen per acre (30 kg/ha) per year was drained from the actively growing clover sward rising to about 117lb N/acre/year (131 kg/ha) when the clover died or was removed. Only 2.3lb/ac (2.5 kg/ha) was drained from the actively growing grass sward. It was estimated that the clover fixed at least 270lb N/ac/year (303 kg/ha/year. The rates of leaching of potassium from a grass sward was about 1.7lb/ac/year (1.9 kg/ha) and 0.8 lb (0.9 kg) phosphorus. The quantities were similar for clover. The grass received from the rain more phosphorus and potassium than was leached but only 60 per cent of the calcium and 13 per cent of the magnesium, similar results being obtained with white clover. During the year of establishment of the grass sward there was evidence of loss of gaseous nitrogen (elemental and/or compound) from the soil: subsequently the nitrogen content of the soil slowly increased. Calcium loss from the bare soil with an average rainfall of 26″ (650 mm) was about 100 lb Ca/ac/year (112 kg/ha).     

INTRAVENOUS NUTRITION—A Clinical Evaluation of a 50 Per Cent Dextrose in Water Solution,Containing 1 mg. of Hydrocortisone per 100 ml

A 50 per cent dextrose in water solution, containing 1 mg. of hydrocortisone per 100 ml., was used successfully in 70 patients for intravenous nutritional maintenance and repletion. There were no adverse systemic effects during or following 216 infusions. The only undesirable local reaction was the rare occurrence of pain in the arm when the concentrated solutions were given too rapidly. Glycosuria was minimal if the infusion rate did not exceed 0.85 gm. of glucose per kilogram of body weight per hour, particularly if 50 units of insulin were added to each 550 ml. bottle of 50 per cent dextrose. In patients without significantly elevated serum potassium content, 30 mEq. of potassium chloride, acetate or phosphate was added to each bottle to prevent hypokalemia.Preliminary observations suggest that this new solution may be given safely intravenously, without need for cutdowns or plastic catheters, if the needle is carefully inserted and well immobilized in the arm vein and the duration of the infusion is not too prolonged. Further studies on the effect of such high caloric supplementation plus protein hydrolysates in parenteral nutritional repletion and maintenance are indicated.     

The dissections of craniocervical arteries

Dissection of craniocervical arteries internal carotid artery (ICA), or vertebral artery (VA) is an increasingly recognized entity and infrequent cause of stroke. We investigated 8 patients (4 women and 4 men) with dissections of the craniocervical arteries. Diagnostic procedures for detection of craniocervical dissection included: extracranial ultrasound-color Doppler flow imaging (CDFI) of carotid and vertebral arteries, transcranial Doppler sonography (TCD) and radiological computed tomography (CT) and digital subtractive angiography (DSA) examinations. Ultrasound findings (CDFI of carotid and vertebral arteries) were positive for vessel dissection in seven patients (or 87.5 per cent) and negative in one patient. DSA was consistent with dissection in five patients (or 62.5 per cent), negative in one, while in two patients the examination was not performed due to known allergy to contrast media. Five patients (62.5 per cent) were treated with anticoagulants, one with suppressors of platelet aggregation, and two patients were operated. Six patients (75 per cent) after the treatment showed partial recovery of neurological defects, and an improvement of ultrasound finding of dissected arteries. In one patient, following operation, stroke developed with deterioration of motor deficit, and one patient was readmitted three months later due to a newly developed stroke and soon died. The diagnosis should be suspected in any young or middle-age patient with new onset of otherwise unexplained unremitting headache or neck ache, especially in association with transient or permanent focal neurological deficits.     

A comparison of euglobulin fractions and whole serum in the hemagglutination and latex fixation tests

One hundred and thirty-two sera were investigated with the Waaler-Rose and latex fixation reactions. The reactions were performed with serum, with acid-precipitated euglobulin, and with cold-precipitated euglobulin. The material consisted of 35 sera from healthy persons, 23 from patients with various diseases, 28 from patients with joint symptoms not due to rheumatoid arthritis, and 46 from patients with classical rheumatoid arthritis.In rheumatoid arthritis sera, an increase in positive reactions was obtained in the Waaler-Rose test from 70 per cent in serum to 83 per cent in acid-precipitated euglobulin. This increase was due to a greater specificity of reactions with low titers. The cold-precipitated euglobulin gave less positive Waaler-Rose reactions than the acid-precipitated euglobulin. With the latex fixation test an increase from 65 per cent positive reactions in serum to about 71 per cent with both cold- and acid-precipitated euglobulin fractions was obtained. Here, the increase consisted of reactions negative in serum but positive in the euglobulin fractions, but again with low titers. Because the increase in positive reactions consists merely of low titer values, fractionation of sera only slightly enhances the reliability of the serological tests.Negatively reacting rheumatoid arthritis sera often had low values of the _2A globulin.     

Effect of sodium in the nutrient medium on the incidence of potassium-deficiency symptoms in tomato plants

Summary Tomato plants (Lycopersicon esculentum cv. Amberley Cross) were grown in sand culture and were fed with four concentrations of potassium nitrate in combination with two levels of sodium nitrate. After six weeks the plants were scored for the presence and absence of a symptom of potassium deficiency, namely, marginal chlorosis and/or necrosis in the young, fully-expanded leaves. These leaves were also analysed for K and Na. Marginal chlorosis and/or necrosis occurred in plants given a nutrient solution containing 0.5 meq K/I or less and supplied with either of the sodium nitrate levels. However, the symptoms occurred more frequently in plants receiving the lower level of sodium nitrate. The laminae on plants receiving the lower concentration of sodium nitrate had a 50 per cent incidence of chlorisis and/or necrosis when the tissue potassium content was 0.74 per cent of the dry wt, while those laminae on plants receiving the higher level did not show a 50 per cent incidence until their potassium fell to 0.64 per cent of the dry wt.     

Some causes of blindness seen at Noor Eye Institute, Afghanistan

This is a survey of the causes of blindness recorded by three students of The City University during a six-week stay at NOOR Eye Institute in Kabul, Afghanistan. The nature of the sample used makes it unsuitable for direct comparison with surveys from other countries. Nevertheless, broad conclusions can be drawn. Severe eye disease is a considerable problem in Afghanistan, in common with other developing countries. The survey included all new patients seen in the outpatient clinic, blind to the extent of being unable to count fingers at more than three metres, in one eye or both. The sample of patients was examined by an ophthalmologist working with our team. A diagnosis was made and various social and demographic questions were asked with the help of an interpreter. In all, 473 patients were examined and included in our survey sample, a very high proportion of the new patients attending the clinic (40.46 per cent). The main causes of blindness were found to be cataract (31.12 per cent), corneal scarring (19.8 per cent), chorioretinal degenerations (6.79 per cent), glaucoma (6.65 per cent) and aphakia (5.52 per cent). Of the major causes of blindness, about forty per cent of the cases were considered remediable, and about thirty per cent could have been prevented. An outstanding difference between the causes of blindness in developed nations and those seen in Afghanistan was the amount of blindness caused by infection, especially in the younger age groups (up to 30 years). Cataract is a major cause of blindness in the older age groups of both societies. People suffering from ocular disease in Afghanistan wait until their sight is badly impaired or lost completely before seeking treatment. This results from a lack of knowledge of what could be done to conserve sight, the irreversible nature of many eye diseases, the distances involved in travelling to the clinic, and even a lack of knowledge of its existence.     

The supply of nutrient ions by diffusion to plant roots in soil

Summary Observation of soil grown roots of rye-grass shows that an approximately cylindrical volume of soil, the root hair cylinder, is densely occupied by root hairs. Estimates are given of the concentration of labile and solution potassium within the root hair cylinder during experiments measuring potassium uptake from two soils by single roots. Calculations, using a diffusion model, suggest that labile potassium concentrations may be reduced to between 99.3 and 53 per cent of the initial, depending on the diffusion characteristics of the soil and nutrient demand by the root. Of the total potassium absorbed by a root in 4 days, the proportion which is supplied from within the root hair cylinder is small (0.8 to 6.3 per cent) indicating that diffusion to the root from the soil outside the root hair cylinder is of paramount importance. When root demand is high, diffusion appears to limit uptake to between 71 and 59 per cent of that which roots of comparable physiology would be expected to absorb from stirred solution of the same concentration. Nevertheless, the presence of root hairs is calculated to have enhanced uptake by up to 77 per cent compared with roots without hairs because they virtually increase the root diameter. Diffusion does not appear to be a limiting factor when root demand is low and hairs can then add little to the efficiency of the root system in potassium absorption.     

Potassium Loss during Galvanotaxis of Slime Mold

The posterior reticulated regions of the plasmodia of the slime mold, Physarum polycephalum, whose migration has been oriented by direct current (3.0 to 5.0 µa/mm² in the agar substrate), contain 30 per cent less potassium than the advancing non-reticulated region. The anterior regions have the same potassium concentration as that of the controls, approximately 32 meq/kg wet weight. Differences in potassium concentration between anterior and posterior regions of control plasmodia, not oriented by electric current, are less than 5 per cent. Sodium, in contrast to potassium, is generally less concentrated in the anterior than in the posterior regions of electrically oriented plasmodia, but sodium concentrations are extremely variable. No significant difference in protein concentration was found between oriented and control plasmodia. Thirty-five per cent of the total potassium, but none of the sodium, is found in acidified ethanol precipitates from plasmodial homogenates. Potassium, but not sodium, appears to be closely associated with processes which differentiate anterior from posterior in an oriented plasmodium.     

EFFECTS OF POTASSIUM ON INDICATOR SPACES AND FLUXES IN SLICES OF BRAIN CORTEX FROM ADULT AND NEW-BORN RATS

—Inulin, sucrose and chloride spaces were measured in slices of brain cortex from adult and from new-born rats incubated in‘balanced', potassium-rich and sodium-rich media. The efflux of the radioactive markers was followed in the two first media and the following results were obtained: (1) In brain slices from new-born rats inulin and sucrose spaces were of identical magnitude (35 per cent). The space magnitude was essentially unaffected by excess potassium. The chloride space was somewhat larger than the inulin (sucrose) space, and the difference increased continuously but relatively slightly with the external potassium concentration. By far the largest amount (i.e. about 90 per cent) of the efflux of radioactive inulin, sucrose and chloride occurred from a rapidly exchanging compartment during incubation in both ‘balanced’ and potassium-rich media. (2) In brain slices from adult rats the inulin space (35 per cent) was significantly smaller than that of sucrose (50 per cent) and of chloride (65 per cent); it seemed to represent the extracellular space relatively well although 10 per cent of the efflux occurred from a slowly exchanging (probably intracellular) compartment. High concentrations of potassium led to a reduction of the inulin space which was probably a result of the concomitant intracellular swelling. The hyperosmolarity per se did not affect the space magnitude, but an increase of the sodium concentration exerted a competitive inhibition of potassium effects on the inulin space. Of the sucrose efflux, 20 per cent occurred from a slowly exchanging compartment in both ‘balanced’ and potassium-rich media, and 30 per cent of the chloride exchanged with this compartment when the tissue was incubated in a ‘balanced’ medium. An increase of the external potassium concentration caused a drastic increase of the chloride space and a reduction of the slowly exhanging fraction of chloride efflux to less than 10 per cent.     

ON THE CHEMICAL COMPOSITION OF THE AXOPLASM OF SQUID GIANT NERVE FIBERS WITH PARTICULAR REFERENCE TO ITS ION PATTERN

Investigations dealing with the determination of the major chemical constituents of the axoplasm of the giant nerve fiber of the squid are described. Particular emphasis has been placed on determining the components involved in acid-base balance. It was found that 72 per cent of the total solids of axoplasm, representing 13.5 per cent of the wet material, are of relatively low molecular weight (dialyzable) and consist mainly of charged ionic or dipolar constituents. Of the 520 micromoles per gm. of total base, 72 per cent are balanced by organic acids: aspartic acid (65 micro equivalents per gm.), glutamic acid (10 micro equivalents), fumaric and succinic acids (15 micro equivalents), a new polycarboxylic acid (35 micro equivalents), and isethionic acid, a biologically novel sulfonic acid (220 micro equivalents). Besides potassium, sodium, small amounts of calcium, and magnesium there is a considerable fraction of organic (nitrogenous) base. Other features of the chemical composition of squid axoplasm include a relatively high concentration of taurine (100 micro equivalents) and an ultraviolet absorbing substance possibly identical with N-methylpicolinic acid. The distribution of the phosphates, especially the concentration of ATP, has been investigated. Specific techniques elaborated in connection with this study have been described and the biochemical implications of the analytical results are discussed.     

The loss of potassium from frog nerves in anoxia and other conditions

1. Frog nerves immersed in Ringer's solution lose on the average 23 per cent more potassium if the solution is equilibrated with pure nitrogen than if equilibrated with oxygen. 2. Tying off the ends of the nerves during immersion increased rather than diminished the loss of potassium. 3. There was some evidence that nerves tended to regain potassium if they were returned to oxygen after a period of anoxia. 4. Addition of acetylcholine to the solution increases the loss of potassium. 5. Equilibration of the solution and nerves with 20 per cent CO₂ in O₂ increases the loss of K from nerves in Ringer's solution but decreases it in frog blood.     

Features of osmotic and ionic regulations in Russian sturgeon (Acipenser güldenst?dti Brandt)

The osmolality of blood serum of one group of Russian sturgeon fished out in Southern Caspian Sea was the same as their habitat, the other group of sturgeons had a serum osmolality several per cent lower than that of sea-water in this part of the Caspian Sea. Ion concentrations in blood serum in sturgens were similar in fresh water and the Caspian Sea. The feature of the Russian sturgeon's kidney is intensive potassium secretion and a comparatively low level of magnesium secretion.