ABSTRACT
pH, C02 and buffer capacity of the brain and blood acid-base status were studied in (C) control and in acutely water depleted (WD) rats. WD rats developed a greater metabolic [H+] increase in brain than in blood. The results suggest that brain [H+] change is a primary metabolic reply to acute dehydration.
Subject(s)
Brain/metabolism , Carbon Dioxide/metabolism , Dehydration/metabolism , Hydrogen-Ion Concentration , Animals , Buffers , Extracellular Space/metabolism , Male , RatsABSTRACT
The arterial (a), mixed venous (v), and arterial-mixed venous differences (A-V) of hydrogen ion concentration ([H+]), PCO2, HCO-3 and base excess (BE) were measured during 3 h in control (C), water-depleted (WD) and water- and salt-depleted (WSD) dogs. In WD animals the difference in hydrogen ion concentration between venous and arterial blood increased because the [H+] increased more in venous than in arterial blood. In WSD animals (A-V) [H+] remained unchanged since both [H+]a and [H+]v increases were parallel. [H+] variations seem to represent the changes in fixed-acid concentration of blood. The difference between both groups of animals in (A-V) [H+] changes could be ascribed to PCO2 variations. [HCO-3] values changed inconsistently. Arterial samples from the experimental groups showed a continuous decrease at the same rate of change. The mean values in WSD were lower than in WD. [HCO-3]v of WSD decreased slowly during the experiment. The rate of decrease of (A-V) [HCO-3] was higher in WD than in WSD. The different behavior of of [HCO-3] between both arterial and mixed venous samples and among experimental groups disappeared if [HCO-3] changes were corrected for bicarbonate generation due to PCO2 variation (respiratory bicarbonate). Thus [HCO-3] corrected for PCO2 variation represents metabolic changes, in good agreement with both [H+] and BE variations. The metabolic acidosis cannot be explained only on the basis of the increase in blood lactate; it is suggested that other fixed acids might contribute to the decrease in blood bicarbonate. In both experimental groups PvCO2 increased continuously. The (A-V) PCO2 showed the same rate of change. There is a good relationship between this increase and the degree of plasma volume change. It therefore might be that PvCO2 increase is a direct consequence of hemodynamic impairment. In WD and WSD, BE decreased progressively in both arterial and mixed venous samples. BEa values were lower than BEv values after the experiment began. (A-V) BE decreased in an exponential manner in both experimental groups; this change could be ascribed to the increased level of deoxygenated hemoglobin in mixed venous blood, thus giving rise to a decrease in fixed acid concentration.
Subject(s)
Acid-Base Equilibrium , Dehydration/blood , Alkalosis , Animals , Bicarbonates/blood , Blood , Carbon Dioxide/blood , Diet, Sodium-Restricted , Dogs , Hydrogen-Ion Concentration , Partial PressureABSTRACT
Plasma volume, hematocrit, protein and electrolyte concentrations in plasma were measured in control and water-deprived rats every three days after starting the experiment until the 15th day. Plasma volume variations, as related to body weight, suggest that water loss from plasma was proportional to total body water at three days and after 9 days of water deprivation. Greater plasma water than body water loss was found during the period between 3 and 9 days. Plasma protein and electrolyte variations suggest that during water deprivation there is a loss of protein, sodium and potassium from plasma, which is proportionally less than that of plasma water. Potassium, calcium and inorganic phosphorus were lost proportionally to plasma water. The variations in plasma volume changes were partially explained as due to variations in plasma protein and electrolyte concentrations.
Subject(s)
Plasma Volume , Water Deprivation , Animals , Blood Proteins/analysis , Body Water/analysis , Electrolytes/blood , Hematocrit , Male , Rats , Time FactorsABSTRACT
To study the variations of blood constituents during water deprivation, rats were deprived of water from six to twelve days. Control and rehydrated animals were also included in the study. A significant increase was observed in sodium, chloride and hematocrit throughout the experiment. Calcium, bicarbonate and PCO2 increased at 10-11 days of treatment. Potassium, inorganic phosphorus, pH, base excess and blood buffer capacity did not change in the course of the experiment. Rehydrated animals recovered to control levels in all the studied components, except for pH and base excess, which increased somewhat. Plasma volume changes could explain only partially electrolyte variation. The "dehydration reaction" is considered to be the main mechanism responsible for these changes. Unchanged hematocrit levels in water deprived animals suggest that after 6 days of water deprivation there is no further loss of plasma water. Bicarbonate and PCO2 changes showed a good relationship and may account for unchanged pH and base excess values.
Subject(s)
Dehydration/blood , Water Deprivation , Acid-Base Equilibrium , Animals , Body Weight , Female , Hydrogen-Ion Concentration , Rats , Water-Electrolyte BalanceABSTRACT
To study the variations of blood constituents during water deprivation, rats were deprived of water from six to twelve days. Control and rehydrated animals were also included in the study. A significant increase was observed in sodium, chloride and hematocrit throughout the experiment. Calcium, bicarbonate and PCO2 increased at 10-11 days of treatment. Potassium, inorganic phosphorus, pH, base excess and blood buffer capacity did not change in the course of the experiment. Rehydrated animals recovered to control levels in all the studied components, except for pH and base excess, which increased somewhat. Plasma volume changes could explain only partially electrolyte variation. The [quot ]dehydration reaction[quot ] is considered to be the main mechanism responsible for these changes. Unchanged hematocrit levels in water deprived animals suggest that after 6 days of water deprivation there is no further loss of plasma water. Bicarbonate and PCO2 changes showed a good relationship and may account for unchanged pH and base excess values.
ABSTRACT
To study the variations of blood constituents during water deprivation, rats were deprived of water from six to twelve days. Control and rehydrated animals were also included in the study. A significant increase was observed in sodium, chloride and hematocrit throughout the experiment. Calcium, bicarbonate and PCO2 increased at 10-11 days of treatment. Potassium, inorganic phosphorus, pH, base excess and blood buffer capacity did not change in the course of the experiment. Rehydrated animals recovered to control levels in all the studied components, except for pH and base excess, which increased somewhat. Plasma volume changes could explain only partially electrolyte variation. The [quot ]dehydration reaction[quot ] is considered to be the main mechanism responsible for these changes. Unchanged hematocrit levels in water deprived animals suggest that after 6 days of water deprivation there is no further loss of plasma water. Bicarbonate and PCO2 changes showed a good relationship and may account for unchanged pH and base excess values.
