Modern quantitative acid-base chemistry

Quantitative analysis of ionic solutions in terms of physical and chemical principles has been effectively prohibited in the past by the overwhelming amount of calculation it required, but computers have suddenly eliminated that prohibition. The result is an approach to acid-base which revolutionizes our ability to understand, predict, and control what happens to hydrogen ions in living systems. This review outlines that approach and suggests some of its most useful implications. Quantitative understanding requires distinctions between independent variables (in body fluids: pCO2, net strong ion charge, and total weak acid, usually protein), and dependent variables [( HCO-3], [HA], [A-], [CO(2-)3], [OH-], and [H+] (or pH]. Dependent variables are determined by independent variables, and can be calculated from the defining equations for the specific system. Hydrogen ion movements between solutions can not affect hydrogen ion concentration; only changes in independent variables can. Many current models for ion movements through membranes will require modification on the basis of this quantitative analysis. Whole body acid-base balance can be understood quantitatively in terms of the three independent variables and their physiological regulation by the lungs, kidneys, gut, and liver. Quantitative analysis also shows that body fluids interact mainly by strong ion movements through the membranes separating them.     

Total weak acid concentration and effective dissociation constant of nonvolatile buffers in human plasma.

The strong ion approach provides a quantitative physicochemical method for describing the mechanism for an acid-base disturbance. The approach requires species-specific values for the total concentration of plasma nonvolatile buffers (A(tot)) and the effective dissociation constant for plasma nonvolatile buffers (K(a)), but these values have not been determined for human plasma. Accordingly, the purpose of this study was to calculate accurate A(tot) and K(a) values using data obtained from in vitro strong ion titration and CO(2) tonometry. The calculated values for A(tot) (24.1 mmol/l) and K(a) (1.05 x 10(-7)) were significantly (P < 0.05) different from the experimentally determined values for horse plasma and differed from the empirically assumed values for human plasma (A(tot) = 19.0 meq/l and K(a) = 3.0 x 10(-7)). The derivatives of pH with respect to the three independent variables [strong ion difference (SID), PCO(2), and A(tot)] of the strong ion approach were calculated as follows: dpH/dSID(+) = [1 + 10(pK(a)-pH)](2)/(2.303 x [SPCO(2)10(pH-pK'(1)[1 + 10(pK(a)-pH](2) + A(tot)10(pK(a)-PH]]; dpH/dPCO(2) = S10(-pK'(1)/[2.303[A(tot)10(pH)(10(pH + 10(pK(a))(-2) - SID(+)10(-pH)]], dpH/dA(tot) = -1/[2.303[SPCO(2)10(pH-pK'(1) + SID(+)10(pK(a)-pH)]], where S is solubility of CO(2) in plasma. The derivatives provide a useful method for calculating the effect of independent changes in SID(+), PCO(2), and A(tot) on plasma pH. The calculated values for A(tot) and K(a) should facilitate application of the strong ion approach to acid-base disturbances in humans.     

Experimental determination of net protein charge, [A]tot, and Ka of nonvolatile buffers in bird plasma.

The quantitative mechanistic acid-base approach to clinical assessment of acid-base status requires species-specific values for [A]tot (the total concentration of nonvolatile buffers in plasma) and Ka (the effective dissociation constant for weak acids in plasma). The aim of this study was to determine [A]tot and Ka values for plasma in domestic pigeons. Plasma from 12 healthy commercial domestic pigeons was tonometered with 20% CO2 at 37 degrees C. Plasma pH, Pco2, and plasma concentrations of strong cations (Na, K, Ca), strong anions (Cl, L-lactate), and nonvolatile buffer ions (total protein, albumin, phosphate) were measured over a pH range of 6.8-7.7. Strong ion difference (SID) (SID5=Na+K+Ca-Cl-lactate) was used to calculate [A]tot and Ka from the measured pH and Pco2 and SID5. Mean (+/-SD) values for bird plasma were as follows: [A]tot=7.76+/-2.15 mmol/l (equivalent to 0.32 mmol/g of total protein, 0.51 mmol/g of albumin, 0.23 mmol/g of total solids); Ka=2.15+/-1.15x10(-7); and pKa=6.67. The net protein charge at normal pH (7.43) was estimated to be 6 meq/l; this value indicates that pigeon plasma has a much lower anion gap value than mammals after adjusting for high mean L-lactate concentrations induced by restraint during blood sampling. This finding indicates that plasma proteins in pigeons have a much lower net anion charge than mammalian plasma protein. An incidental finding was that total protein concentration measured by a multianalyzer system was consistently lower than the value for total solids measured by refractometer.     

Cerebrospinal fluid ions in metabolic acidosis in dogs: effects of acetazolamide

We hypothesized that, during isosmotic isonatremic HCl acidosis with maintained isocapnia in cisternal cerebrospinal fluid (CSF), acetazolamide, by inhibiting carbonic anhydrase (CA) in the central nervous system (CNS), should produce an isonatric hyperchloric metabolic acidosis in CSF. Blood and CSF ions and acid-base variables were measured in two groups of anesthetized and paralyzed dogs with bilateral ligation of renal pedicles during 5 h of HCl acidosis (plasma [HCO3-] = 11 meq/l). Mechanical ventilation was regulated such that arterial PCO2 dropped and CSF Pco2 remained relatively constant. In group I (control group, n = 6), CSF [Na+] remained unchanged, [HCO3-] and strong ions difference (SID) fell, respectively, 6.1 and 5 meq/l, and [Cl-] rose 3.5 meq/l after 5 h of acidosis. In acetazolamide-treated animals, (group II, n = 7), CSF [Na+] remained unchanged, [HCO3-], and SID fell 11 and 7.1 meq/l, respectively, and [Cl-] rose 7.1 meq/l. We conclude that during HCl acidosis inhibition of CNS CA by acetazolamide induces an isonatric hyperchloric metabolic acidosis in CSF, which is more severe than that observed in controls.     

Control of active proton transport in turtle urinary bladder by cell pH

The rate of active H+ secretion (JH) across the luminal cell membrane of the turtle bladder decreases linearly with the chemical (delta pH) or electrical potential gradient (delta psi) against which secretion occurs. To examine the control of JH from the cell side of the pump, acid-base changes were imposed on the cellular compartment by increasing serosal[HCO3-] at constant PCO2 or by varying PCO2 at constant [HCO3-]. When serosal [HCO3-] was increased from 0 to 60 mM, cell [H+] decreased, as estimated by the 5,5-dimethyloxazoladine-2,4- dione method. JH was a saturable function of cell [H+], with an apparent Km of 25 nM. When PCO2 was varied between 1 and 20% at various serosal Km of 25 nM. When PCO2 was varied between 1 and 20% at various serosal [HCO3-], the PCO2 required to reach a maximal JH increased with [HCO3-] so that JH was a function of cell [H+] rather than of cell [HCO3-] or CO2. The proton pump was controlled asymmetrically with respect to the pH component of the electrochemical potential for protons, microH. On the cell side of the pump, a delta pH of < 1 U was required to vary JH between maximal and zero values, whereas on the luminal side a delta pH of 3 U was required. Cell [H+] regulates JH by determining the availability of H+ to the pump in a relationship resembling Michaelis-Menten kinetics. Increasing luminal [H+] generates an energy barrier at a luminal pH near 4.4 that equals the free energy (per H+ translocated) of the metabolic driving reaction.     

Intracellular pH regulation in the renal proximal tubule of the salamander. Basolateral HCO3- transport

We have used pH-, Na-, and Cl-sensitive microelectrodes to study basolateral HCO3- transport in isolated, perfused proximal tubules of the tiger salamander Ambystoma tigrinum. In one series of experiments, we lowered basolateral pH (pHb) from 7.5 to 6.8 by reducing [HCO3-]b from 10 to 2 mM at a constant pCO2. This reduction of pHb and [HCO3-]b causes a large (approximately 0.35), rapid fall in pHi as well as a transient depolarization of the basolateral membrane. Returning pHb and [HCO3-]b to normal has the opposite effects. Similar reductions of luminal pH (pHl) and [HCO3-]l have only minor effects. The reduction of [HCO3-]b and pHb also produces a reversible fall in aiNa. In a second series of experiments, we reduced [Na+]b at constant [HCO3-]b and pHb, and also observed a rapid fall in pHi and a transient basolateral depolarization. These changes are reversed by returning [Na+]b to normal. The effects of altering [Na+]l in the presence of HCO3-, or of altering [Na+]b in the nominal absence of HCO3-, are substantially less. Although the effects on pHi and basolateral membrane potential of altering either [HCO3-]b or [Na+]b are largely blocked by 4-acetamido-4- isothiocyanostilbene-2,2'-disulfonate (SITS), they are not affected by removal of Cl-, nor are there accompanying changes in aiCl consistent with a tight linkage between Cl- fluxes and those of Na+ and HCO3-. The aforementioned changes are apparently mediated by a single transport system, not involving Cl-. We conclude that HCO3- transport is restricted to the basolateral membrane, and that HCO3- fluxes are linked to those of Na+. The data are compatible with an electrogenic Na/HCO3 transporter that carries Na+, HCO3-, and net negative charge in the same direction.     

The roles of ion fluxes in skeletal muscle fatigue

Intense muscle contractions result in large changes in the intracellular concentrations of electrolytes. The purpose of this study was to examine the contributions of changes in intracellular strong ions to calculated changes in steady-state membrane potential (Em) and muscle intracellular H+ concentration ([H+]i). A physicochemical model is used to examine the origin of the changes in [H+]i during intense muscle contraction. The study used the isolated perfused rat hindlimb intermittently stimulated to contract at high intensity for 5 min. This resulted in significant K+ depletion of both slow (soleus) and fast (white gastrocnemius, WG) muscle fibers and a release of K+ and lactate (Lac-) into venous perfusate. The major contributor to a 12- to 14-mV depolarization of Em in soleus and WG was the decrease in intracellular K+ concentration ([K+]i). The major independent contributors to [H+]i are changes in the concentrations of strong and weak ions and in CO2. Significant decreases in the strong ion difference [( SID]i) in both soleus and WG contributed substantially to the increase in [H+]i during stimulation. In WG the model showed that the decrease in [SID]i accounted for 35% of the increase in [H+]i (133-312 nequiv/L; pHi = 6.88-6.51) at the end of stimulation. Of the main contributors to decreased [SID]i, increased [Lac-]i and decreased [K+]i contributed 40 and 60%, respectively, to increased [H+]i, whereas a decrease in [PCr2-]i contributed to reduced [H+]i. It is concluded that decreased muscle [K+]i during intense contractions is the single most important contributor to reduced Em and increased [H+]i. Depletion of PCr2- simultaneous to the changes in [Lac-]i and [K+]i prevents larger increases in [H+]i and helps maintain the intracellular acid-base state.     

Ionic mechanisms of cerebrospinal fluid acid-base regulation

This review emphasizes the importance of strong ions in the regulation of cerebrospinal fluid (CSF) acid-base balance. In a solution like CSF that is devoid of nonbicarbonate buffers. [H+] and [HCO-3] are dependent variables, the independent variables being the CO2 partial pressure (PCO2) and the strong ion difference. Any measureable changes in CSF [HCO-3] and any change in [H+] that occur independent of changes in PCO2 must be accompanied by, if not caused by, changes in strong ions. The role of H+ and HCO-3 vs. strong ions in the ionic mechanisms of CSF acid-base regulation is unknown. For example, these mechanisms could depend only on changes in strong ions that accompany acid-base disorders, or they could be triggered by changes in [H+] or PCO2. These ideas are presented within the context of current concepts concerning the relationship of CSF to brain interstitial fluid (ISF) and the importance of choroid plexus and blood-brain barrier mechanisms in determining CSF and ISF ionic composition. Studies concerning CSF strong ions in normal and abnormal acid-base states are reviewed.     

Roles of CO2, O2, and acid in arteriovenous [H+] difference during muscle contractions

To determine the origins of the arteriovenous [H+] difference of muscle during contractions, arterial and muscle venous blood sample pairs were taken before and after 0.5, 5.0, and 30.0 min of 4/s isometric twitches of the gastrocnemius-plantaris muscle group of anesthetized dogs. These samples were analyzed for PO2, PCO2, and pH, the concentrations of O2, CO2, K+, Na+, La-, and Cl- in whole blood, and La-, K+, Na+, and Cl- in plasma. Whole blood was hemolyzed and analyzed for PO2, PCO2, and pH. Net O2 uptake, CO2 output, L, K+, Na+, and Cl- were calculated in addition to net output of non-CO2 acid (HA) and strong ion difference ([SID]) and common ion [SID] ([K+] + [Na+] - [Cl-] - [La-]). From these data we partitioned the origins of the arteriovenous [H+] difference via the common PCO2-pH diagram and via a [H+]-PCO2 diagram and determined whether true plasma arteriovenous [H+] differences reflect plasma and cell arteriovenous [H+] differences. The arteriovenous [H+] differences of plasma and hemolyzed blood were the same, showing that true plasma does reflect plasma and cells. K+ showed a small significant but transient output. Na+ was not significant, whereas Cl- showed a significant transient uptake. Lactate output and HA, calculated for dog blood acid-base, showed transient outputs and were the same. At 5.0 min when the arteriovenous difference was largest, CO2 alone would have increased [H+] 15.9 nmol/l whereas desaturation of Hb would have decreased [H+] 4.2 nmol/l and lactate could have raised [H+] 1.0 nmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bicarbonate concentration and osmolality are key determinants in the inhibition of CHO cell polysialylation under elevated pCO(2) or pH.

Accumulation of CO(2) in animal cell cultures can be a significant problem during scale-up and production of recombinant glycoprotein biopharmaceuticals. By examining the cell-surface polysialic acid (PSA) content, we show that elevated CO(2) partial pressure (pCO(2)) can alter protein glycosylation. PSA is a high-molecular-weight polymer attached to several complex N-linked oligosaccharides on the neural cell adhesion molecule (NCAM), so that small changes in either core glycosylation or in polysialylation are amplified and easily measured. Flow-cytometric analysis revealed that PSA levels on Chinese hamster ovary (CHO) cells decrease with increasing pCO(2) in a dose-dependent manner, independent of any change in NCAM content. The results are highly pH-dependent, with a greater decrease in PSA at higher pH. By manipulating medium pH and pCO(2), we showed that decreases in PSA correlate well with bicarbonate concentration ([HCO(3)(-)]). In fact, it was possible to offset a 60% decrease in PSA content at 120 mm Hg pCO(2) by decreasing the pH from 7.3 to 6.9, such that [HCO(3)(-)] was lowered to that of control (38 mm Hg pCO(2)). When the increase in osmolality associated with elevated [HCO(3)(-)] was offset by decreasing the basal medium [NaCl], elevated [HCO(3)(-)] still caused a decrease in PSA, although less extensive than without osmolality control. By increasing [NaCl], we show that hyperosmolality alone decreases PSA content, but to a lesser extent than for the same osmolality increase due to elevated [NaHCO(3)]. In conclusion, we demonstrate the importance of pH and pCO(2) interactions, and show that [HCO(3)(-)] and osmolality can account for the observed changes in PSA content over a wide range of pH and pCO(2) values.     

Effect of fasting and acute heat stress on body temperature, blood acid-base and electrolyte status in chickens

1. The tolerance of chickens to acute heat stress, evaluated by the time required to reach the critical body temperature (Tr) of 44.5 degrees C, was markedly enhanced as the period of fasting was extended. 2. Fasting reduced the rates of heat-induced changes in blood acid-base and electrolyte status. 3. Changes in Tr were correlated with changes in blood pH, pCO2, [Cl-] and [Pi] but not with changes in [Na+] or [K+]. 4. Blood acid-base and electrolyte status were related to Tr rather than time of exposure to heat stress.     

Ventral medullary extracellular fluid pH and PCO2 during hypoxemia

We designed experiments to study changes in ventral medullary extracellular fluid (ECF) PCO2 and pH during hypoxemia. Measurements were made in chloralose-urethan-anesthetized spontaneously breathing cats (n = 12) with peripherial chemodenervation. Steady-state measurements were made during normoxemia [arterial PO2 (PaO2) = 106 Torr], hypoxemia (PaO2 = 46 Torr), and recovery (PaO2 = 105 Torr), with relatively constant arterial PCO2 (approximately 44 Torr). Mean values of ventilation were 945, 683, and 1,037 ml/min during normoxemia, hypoxemia, and recovery from hypoxemia, respectively. Ventilatory depression occurred in each cat during hypoxemia. Mean values of medullary ECF PCO2 were 57.7 +/- 7.2 (SD), 59.4 +/- 9.7, and 57.4 +/- 7.2 Torr during normoxemia, hypoxemia, and recovery to normoxemia, respectively; respective values for ECF [H+] were 60.9 +/- 8.0, 64.4 +/- 11.6, and 62.9 +/- 9.2 neq/l. Mean values of calculated ECF [HCO3-] were 22.8 +/- 3.0, 21.7 +/- 3.3, and 21.4 +/- 3.1 meq/l during normoxemia, hypoxemia, and recovery, respectively. Changes in medullary ECF PCO2 and [H+] were not statistically significant. Therefore hypoxemia caused ventilatory depression independent of changes in ECF acid-base variables. Furthermore, on return to normoxemia, ventilation rose considerably, still independent of changes in ECF PCO2, [H+], and [HCO3-].     

Monitoring of blood gas parameters and acid-base balance of pregnant and non-pregnant rabbits (Oryctolagus cuniculus) in routine experimental conditions.

Blood gas parameters and acid-base balance values were determined in adult pregnant New Zealand rabbits (Oryctolagus cuniculus) in standard laboratory housing conditions and during anaesthesia with an association of ketamine-chlorpromazine, administered before surgical procedures. All the variables were also studied in adult non-pregnant female, used as controls. No differences in pH, sO2c, O2Hb, COHb, sO2m and a-vDO2 were found between pregnant and non-pregnant rabbits in physiological conditions and during anaesthesia. Ketamine-chlorpromazine and pregnancy seemed to change the other parameters used to assess the acid-base balance and the oxygenation conditions. Anaesthesia affected only Hb, O2Ct, O2Cap, CcO2 and P50. The additive effect of pregnancy and anaesthesia modified pCO2, pO2, HCO3-, TCO2, BEb, SBC, BEecf, A-aDO2, RI, MetHb, RHb, CaO2 and CvO2. The patterns described are close to those of other species, suggesting the New Zealand rabbit might be a reliable animal model for monitoring selected variables.     

Na(+)-dependent Cl-HCO3 exchange in the squid axon. Dependence on extracellular pH.

Intracellular pH (pHi) in squid giant axons recovers from acid loads by means of a Na(+)-dependent Cl-HCO3 exchanger, the actual mechanism of which might be exchange of: (i) external Na+ and HCO3- for internal Cl- and H+, (ii) Na+ plus two HCO3- for Cl-, (iii) Na+ and CO3= for Cl-, or (iv) the NaCO3- ion pair for Cl-. Here we examine sensitivity of transport to changes of extracellular pH (pHo) in the range 7.1-8.6. We altered pHo in four ways, using: (i) classical "metabolic" disturbances in which we varied [HCO3-]o, [NaCO3-]o, and [CO3=]o at a fixed [CO2]o; (ii) classical "respiratory" disturbances in which we varied [CO2]o, [NaCO3-]o, and [CO3=]o at a fixed [HCO3-]o; (iii) novel mixed-type acid-base disturbances in which we varied [HCO3-]o and [CO2]o at a fixed [CO3=]o and [NaCO3-]o; and (iv) a second series of novel mixed-type disturbances in which we varied [CO2]o, [CO3=]o, and [Na+]o at a fixed [HCO3-]o and [NaCO3-]o. Axons (initial pHi approximately 7.4) were internally dialyzed with a pH 6.5 solution containing 400 mM Cl- but no Na+. After pHi, measured with a glass microelectrode, had fallen to approximately 6.6, dialysis was halted. The equivalent acid extrusion rate (JH) was computed from the rate of pHi recovery (i.e., increase) in the presence of Na+ and HCO3-. When pHo was varied by method (i), which produced the greatest range of [CO3=]o and [NaCO3-]o values, JH increased with pHo in a sigmoidal fashion; the relation was fitted by a pH titration curve with a pK of approximately 7.7 and a Hill coefficient of approximately 3.0. With method (ii), which produced smaller changes in [CO3=]o and [NaCO3-]o, JH also increased with pHo, though less steeply. With method (iii), which involved changes in neither [CO3=]o nor [NaCO3-]o, JH was insensitive to pHo changes. Finally, with method (iv), which involved changes in neither [HCO3-] nor [NaCO3-]o, but reciprocal changes in [CO3=]o and [Na+]o, JH also was insensitive to pHo changes. We found that decreasing pHo from 8.6 to 7.1 caused the apparent Km for external HCO3- ([Na+]o = 425 mM) to increase from 1.0 to 26.7 mM, whereas Jmax was relatively stable. Decreasing pHo from 8.6 to 7.4 caused the apparent Km values for external Na+ ([HCO3-]o = 48 mM) to increase from 8.6 to 81 mM, whereas Jmax was relatively stable.(ABSTRACT TRUNCATED AT 400 WORDS)     

大耳白兔动脉血和脑脊液酸碱电解质值及其相互关系

３０只正常大耳白兔,经股动脉穿刺插管和枕骨下经皮穿刺入枕骨下池,在严格隔绝空气情况下,分别取得动脉血和脑脊液（ＣＳＦ）标本,用ＡＢＬ３型血气分析仪及ＣＮ６４４型生化分析仪检测主要酸碱变量及电解质值。经统计学处理结果表明：ＣＳＦｐＨｅｙ ｋ＾＋、Ｃａ＾２＋、Ｍｇ＾２＋浓度〈动脉血,ＣＳＦＰＣＯ２及ＨＣＯ３＾－、Ｃｌ＾－Ｎａ＾＿、Ｈ＾＋〉动脉血。另外,ＣＳＦＰＨ与ｐＨａ,ＣＳＦＰＣＯ２与ＰａＣＯ２、Ｃ     

Cytosolic pH regulation in osteoblasts. Regulation of anion exchange by intracellular pH and Ca2+ ions

Measurements of cytosolic pH (pHi) 36Cl fluxes and free cytosolic Ca2+ concentration ([Ca2+]i) were performed in the clonal osteosarcoma cell line UMR-106 to characterize the kinetic properties of Cl-/HCO3- (OH-) exchange and its regulation by pHi and [Ca2+]i. Suspending cells in Cl(-)-free medium resulted in rapid cytosolic alkalinization from pHi 7.05 to approximately 7.42. Subsequently, the cytosol acidified to pHi 7.31. Extracellular HCO3- increased the rate and extent of cytosolic alkalinization and prevented the secondary acidification. Suspending alkalinized and Cl(-)-depleted cells in Cl(-)-containing solutions resulted in cytosolic acidification. All these pHi changes were inhibited by 4',4',-diisothiocyano-2,2'-stilbene disulfonic acid (DIDS) and H2DIDS, and were not affected by manipulation of the membrane potential. The pattern of extracellular Cl- dependency of the exchange process suggests that Cl- ions interact with a single saturable external site and HCO3- (OH-) complete with Cl- for binding to this site. The dependencies of both net anion exchange and Cl- self-exchange fluxes on pHi did not follow simple saturation kinetics. These findings suggest that the anion exchanger is regulated by intracellular HCO3- (OH-). A rise in [Ca2+]i, whether induced by stimulation of protein kinase C-activated Ca2+ channels, Ca2+ ionophore, or depolarization of the plasma membrane, resulted in cytosolic acidification with subsequent recovery from acidification. The Ca2+-activated acidification required the presence of Cl- in the medium, could be blocked by DIDS, and H2DIDS and was independent of the membrane potential. The subsequent recovery from acidification was absolutely dependent on the initial acidification, required the presence of Na+ in the medium, and was blocked by amiloride. Activation of protein kinase C without a change in [Ca2+]i did not alter pHi. Likewise, in H2DIDS-treated cells and in the absence of Cl-, an increase in [Ca2+]i did not activate the Na+/H+ exchanger in UMR-106 cells. These findings indicate that an increase in [Ca2+]i was sufficient to activate the Cl-/HCO3- exchanger, which results in the acidification of the cytosol. The accumulated H+ in the cytosol activated the Na+/H+ exchanger. Kinetic analysis of the anion exchange showed that at saturating intracellular OH-, a [Ca2+]i increase did not modify the properties of the extracellular site. A rise in [Ca2+]i increased the apparent affinity for intracellular OH- (or HCO3-) of both net anion and Cl- self exchange. These results indicate that [Ca2+]i modifies the interaction of intracellular OH- (or HCO3-) with the proposed regulatory site of the anion exchanger in UMR-106 cells.     

Newborn puppy cerebral acid-base regulation in experimental asphyxia and recovery

We hypothesized that part of the newborn tolerance of asphyxia involves strong ion changes that minimize the cerebral acidosis and hasten its correction in recovery. After exposure of newborn puppies to 15 or 30 min experimental asphyxia (inhalation of gas with fractional concentration of CO2 and of O2 in inspired gas = 0.07-0.08 and 0.02-0.03, respectively), blood lactate increased to 13.2 and 23.4 mmol/l, respectively, brain tissue lactate increased to 14.4 and 19.7 mmol/kg, and cerebrospinal fluid (CSF) lactate increased to 7.6 and 14.4 mmol/l. We presume that the tissue lactate increase reflects increases in brain cell and extracellular fluid lactate concentration. The lactate increase, a change that will decrease the strong ion difference (SID), [HCO3-], and pH, was accompanied by increases in Na+ (plasma, CSF, brain), K+ (plasma, CSF), and osmolality without change in Cl-. After 60-min recovery, plasma and brain lactate decreased significantly, but CSF lactate remained unchanged. [H+] recovery was more complete than that of the strong ions due to hyperventilation-induced hypocapnia. We conclude that during asphyxia-induced lactic acidosis, changes in strong ions occur that lessen the decrease in SID and minimize the acidosis in plasma and CSF. To the extent that the increase in brain tissue sodium reflects increases in intra-and extracellular fluid sodium concentration, the decrease in SID will be less in these compartments as well. In recovery, CSF ionic values change little; plasma and brain tissue lactate decrease with a similar time course, and the [H+] is rapidly returned toward normal by hypocapnia even while the SID is below normal.     

Changes in smooth muscle cell pH during hypoxic pulmonary vasoconstriction: a possible role for ion transporters

Hypoxic pulmonary vasoconstriction (HPV) occurs in smooth muscle cells (SMC) from small pulmonary arteries (SPA) and is accompanied by increases in free cytoplasmic calcium ([Ca2+]i) and cytoplasmic pH (pHi). SMC from large pulmonary arteries (LPA) relax during hypoxia, and [Ca2+]i and pHi decrease. Increases in pHi and [Ca2+]i in cat SPA SMC during hypoxia and the augmentation of hypoxic pulmonary vasoconstriction by alkalosis seen in isolated arteries and lungs suggest that cellular mechanisms, which regulate inward and outward movement of Ca2+ and H+, may participate in the generation of HPV. SMC transport systems that regulate pHi include the Na+ - H+ transporter which regulates intracellular Na+ and H+ and aids in recovery from acid loads, and the Na+ -dependent and Na+ -independent Cl-/HCO3- transporters which regulate intracellular chloride. The Na+ -dependent Cl-/HCO3- transporter also aids in recovery from acidosis in the presence of CO2 and HCO3-. The Na+ -independent Cl-/HCO3- transporter aids in recovery from cellular alkalosis. The Na+ - H+ transporter was present in SMC from SPA and LPA of the cat, but it seemed to have little if any role in regulating pHi in the presence of CO2 and HCO3-. Inhibiting the Cl-/HCO3- transporters reversed the normal direction of pHi change during hypoxia, suggesting a role for these transporters in the hypoxic response. Future studies to determine the interaction between pHi, [Ca2+]i and HPV should ascertain whether pHi and [Ca2+]i changes are linked and how they may interact to promote or inhibit SMC contraction.     

Physiology and chemistry of cerebrospinal fluid, aqueous humor and endolymph in Squalus acanthias.

By means of the appropriate isotopes injected into the spiny dogfish, Squalus acanthias, the transfer of all major ions into cerebrospinal fluid (CSF), aqueous humor (A) and endolymph (E) was studied. In addition, the effect of raising pCO2 in sea-water upon HCO3- concentration of these fluids was measured. In the several types of experiments, acetazolamide or methazolamide was used to inhibit completely carbonic anhydrase. The rates of fluid formation and ion transfer in CSF and A were fairly close, but those for E were far slower. The general pattern of ion transport in the three fluids were the same, Na+ (or Na+ + K+ in E) entry greater than Cl - entry, and the difference was HCO3-. The greater rate constants for HCO3-, increase in its entry rate by elevation of pCO2, and inhibition of its appearance by the sulfonamides, show that this is a special case of transport; the ion is formed in secretory cells from gaseous CO2 + OH-. Secretory cells at sites of formation of all the fluids contain both carbonic anhydrase and Na+-K+-ATP-ase, which subserve HCO3- formation and Na+ (or K+) transport. Comparison of these results with studies in mammals show that the vertebrate pattern for secretion of these three fluids is well established in the elasmobranch.     

正常麻醉犬动脉血和脑脊液酸碱及电解质值

２０条正常麻醉犬经股动脉插管和枕骨下经皮穿刺在严格隔绝空气情况下，分别取得动脉血和脑脊液（ＣＳＦ）样本，用ＩＬ－１３０３型血气分析仪和Ｂｅｃｋｍａｎ－７００型生化分析仪检测酸碱变量及电解质。通过酶反应分光光度法检测乳酸（Ｌａｃｔ）。应用（Ｎａ＋＋Ｋ＋）－（Ｃｌ－＋Ｌａｃｔ＋ＨＣＯ３－）公式计算阴离子隙（ＡＧ）。经统计学处理结果表明ＣＳＦＰＨ、Ｋ＋、ＡＧ＜动脉血（ｐ＜０．０１）；ＣＳＦＰＣＯ２、ＨＣＯ３－、Ｃｌ－、Ｌａｃｔ＞动脉血（ｐ＜０．０１）；ＣＳＦＮａ＋同动脉血比较无明显差异（ｐ＞０．０５）。