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We measured the pH of airway surface liquid (ASL) secreted by the ferret trachea in vitro by using a catheter-tipped pH electrode implanted in a collecting cannula close to the airway epithelium. Mucus secretion was promoted by methacholine (0.02 mmol/l) in the organ bath. The pH of the ASL was 6.85 +/- 0.03 (SE) compared with a bath value of 7.39 +/- 0.01, when the bath was bubbled with 5.65% CO2. Changing the bath CO2 from 0 to 20.93% CO2 altered the bath pH from 8.06 to 6.96, but the ASL pH only varied from 6.92 to 6.85. This homeostasis of ASL pH was not the result of the buffering powers of the ASL, because ex situ buffer curves for secreted ASL were similar to those for Krebs-Henseleit solution. Changing the luminal CO2 content by blowing gases through the trachea changed ASL pH by values similar to that ex situ. However, when external organ bath CO2 was changed, the luminal CO2 changes were proportionately far smaller. Measurement of rates of diffusion of CO2 across the tracheal wall indicated that this was not a limiting factor in the results. Similarly, measurement of metabolic rate CO2 production in the tracheal lumen indicated that this did not significantly affect the results. We conclude that the pH of ASL is significantly on the acid side of the pH or interstitial fluid and plasma and that it is maintained relatively constant despite large changes in external pH.

Single skins were analyzed by 31P-nuclear magnetic resonance (NMR) spectroscopy during alternate perfusion with control and experimental solutions. Intracellular (pHc) and extracellular (pHo) pH were monitored by measuring the spectral frequencies of intracellular Pi and external methylphosphonate, respectively. Base-line pHc was 7.20 +/- 0.02 (SE) when pHo was 6.99 +/- 0.02. A 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS)-inhibitable, HCO3--dependent alkaline shift in pHc can be elicited by replacing external Cl- by gluconate or sulfate. We now report that this effect is observed even in sodium-free media. The substitution of gluconate for external Cl- has also been reported to shrink cell volume. This shrinkage can be minimized by replacing Cl- with gluconate during perfusion with hypotonic, rather than isotonic, media. Conducted in this manner, the anionic substitution produces a much smaller alkaline shift in pHc. Replacement of external NaCl with N-methyl-D-glucamine chloride acidified the cells reversibly by 0.22 +/- 0.02. In the presence of the Na-H antiport blocker 5-(N-methyl-N-isobutyl)amiloride (MIA), restoration of external Na+ did not increase pHc. Separate addition of MIA acidified the cells by 0.18 +/- 0.03. Adenosine 3',5'-cyclic monophosphate (cAMP) also alters pHc. Addition of 1 mM 8(4-chlorophenylthio)cAMP or 100 mU/ml vasopressin acidified the cells by 0.22 +/- 0.03 and by 0.14 +/- 0.04, respectively. The data suggest that frog skin regulates pHc by the parallel operation of Na-H and Na+-independent Cl-HCO3 antiports. Cell volume and cAMP may play regulating roles in this epithelium.

The effects of glucagon and PTH on renal tubular electrolyte handling were studied in anesthetized, thyroparathyroidectomized Brattleboro rats infused with somatostatin. Fractional excretion of Ca and Mg was significantly lower during infusion of both hormones. Micropunctures of same nephrons localized the bulk of the increase in reabsorption in Henle's loop, where both hormones significantly enhanced the reabsorptive capacities for Ca, Mg, and K. Beyond the early distal tubule, Ca and Mg reabsorption was significantly greater during glucagon infusion and Ca reabsorption was significantly greater during PTH infusion. Cyclic adenosine monophosphate at a plasma concentration of 10(-6) M did not reproduce the effects of either glucagon or PTH. These results are similar to the findings reported for the effects of ADH and calcitonin on Ca, Mg, and K tubular handling, but different as far as Na and Cl are concerned, since their loop reabsorption was not significantly altered by glucagon and PTH. The data obtained here for glucagon and PTH, together with those for ADH and calcitonin, support the hypothesis that these four hormones exert similar effects in the thick ascending limb.

The control of androgen concentrations in the intraluminal fluids of the male reproductive tract is not well understood. The present experiments were performed to determine the effects of hypophysectomy, hypophysectomy plus testosterone (T), and hypophysectomy plus pregnenolone treatment on intraluminal androgen concentrations in the adult rat testis and epididymis. T and 5 alpha-dihydrotestosterone (DHT) concentrations were determined in the vascular, interstitial, and intraluminal compartments of the epididymis. Testicular and epididymal morphology also were examined under light microscopy. Hypophysectomy of at least 5 days duration significantly reduced T and DHT concentrations in serum, tissues, and intraluminal fluids of the reproductive tract. T replacement for 14 days, which produced peripheral T concentrations of 5 ng/ml, did not support intraluminal androgen concentrations in the seminiferous tubules equivalent to controls; rete testis androgen concentrations were similar to controls, however. Pregnenolone administration at 2 mg X rat-1 X day-1 for 14 days did not maintain spermatogenesis nor intraluminal T concentrations in the seminiferous tubules equivalent to controls; however, a low level of spermatogenesis continued when intraluminal and tissue androgen concentrations were maintained at 10-20% of controls by either the testosterone and pregnenolone treatments.

Volumes of 10(-10) liter of sweat, saliva, and urine were analyzed with an energy-dispersive spectrometer (EDS) X-ray analyzer on a standard scanning electron microscope (SEM). Results of the EDS analysis of diluted and undiluted samples were verified by comparison with results of analyses of the same sample prepared by conventional quantitative methods. Except for Cl in concentrated urines and Mg in low concentrations, good agreement was found between the methods. The analysis provides quantitation of most elements of biological interest present in concentrations of about 1 mM, while it demonstrates good linearity (r greater than 0.99) throughout a wide range of commonly encountered biological concentrations. Reproducibility of the analysis is on the order of 2% and the minimal determinable concentration is generally between 0.5 and 1.0 mM for S, P, K, and Ca and slightly more than 1.0 mM for Mg.

Because estrogens have been reported to produce sodium retention, this study investigated the possibility that hypertension in rats resulting from the ingestion of an estrogen used as an oral contraceptive could be due to increases in body fluid volumes. Female rats were given feed containing mestranol for 1, 3, and 6 mo; control rats were given the feed without mestranol. The mestranol-treated rats had higher arterial pressures than the controls only after 6 mo of treatment. Plasma volume, extracellular fluid volume, and total body water were measured in each rat by the distribution volumes of radioiodinated serum albumin, 35SO4, and tritiated water, respectively. Values for blood volume, interstitial fluid volume, and intracellular fluid volume were derived from these measurements. These body fluid volumes, expressed per 100 g of body weight, were not different between the mestranol-treated rats and their controls at any of the three treatment times. Due to differences in body weight and lean body mass between the mestranol-treated and the control rats, these volumes also were expressed per 100 g of lean body mass. Again, no differences were observed between the mestranol-treated rats and the control rats for any of these body fluid compartments at any of the treatment times. These studies, therefore, were unable to provide evidence that increases in body fluid volumes contributed to the elevated arterial pressure in this rat model of oral contraceptive hypertension.

Cows having free access to water (hydrated) or deprived of water for 26.5 h (dehydrated) were infused for 3 h with angiotensin II or captopril solutions intravenously (iv) or intracerebroventricularly (icv) beginning 1 h before access to 0.3 M NaHCO3/NaCl solution for 2 h. The results agree with the results of the experiments with the same agents and doses in Na-deficient cows. Only iv infusion of angiotensin II stimulated Na appetite and only icv infusion of angiotensin II stimulated thirst. Therefore, barriers to the penetration of angiotensin II in the brain determined the particular site of action and elicited response. Dehydration did not stimulate Na appetite and, as shown previously, Na deficiency did not stimulate thirst, but both behaviors seem to be influenced by angiotensin-related mechanisms in the brain. The inability of iv angiotensin II to stimulate Na appetite in hydrated cows might be explained by the lack of a response caused by, and common to, Na deficiency and dehydration, e.g., upregulation of angiotensin II receptors, or reduced extracellular fluid volume.

A method was established to analyze the extracellular water space (H2Oe) in small muscle tissue samples as [3H]inulin distribution space. After initial experiments on rats, the method was applied on 13 men and 6 women. Muscles with different fiber compositions (soleus, S; vastus lateralis, (VL; gastrocnemius, G; triceps brachii, TB) were studied at rest. The total water content was the same for all muscles, 320 (313-330) ml/100 g dry wt. However, differences were demonstrated for H2Oe, with 26-34 ml/100 g dry wt in VL and 38-54 ml/100 g dry wt in S, (P less than 0.05); the values for G and TB were in between those for VL and S. The differences in H2Oe were not related to the fiber composition of the muscles. During 3 x 3 min of intense bicycle exercise demanding about 120% VO2 max (6 men), total water content increased in VL from 313 to 359 ml/100 g dry wt and H2Oe increased from 34 to 60 ml/100 g dry wt (P less than 0.05), In TB, which is relatively inactive during bicycle exercise, no such changes occurred. The calculated intracellular lactate concentration increased in VL from 5.7 to 30.6 mmol/l H2Oi. The extracellular lactate concentration amounted to 13.6 mmol/l H2Oe at the end of exercise. The concentration gradient for lactate of 2 from intra- to extracellular space favored a flux of water to the intracellular space. The relative large increase in H2Oe may then be caused by a hydrostatic rather than an osmotic factor.U

We measured the flux of albumin between the vascular space and the pulmonary interstitial and luminal lining fluids in 20 adult sheep with chronic lung lymph fistulas. We sampled the bronchoalveolar lining layer by episodic fiberbronchoscopic lavage. A total of 62 alveolar lavages were performed at times ranging between 30 min and 60 h after intra-arterial injection of 100 microCi of 125I-labeled albumin. Samples of lymph and plasma were obtained simultaneously with lavage fluid, and the radioactivity and albumin content of all samples were measured and expressed as specific activity (counts/min . g albumin). We found that alveolar lavage fluid collected by our technique is not significantly contaminated by plasma or interstitial fluid proteins. Proteins present in alveolar lavage fluid and also present in plasma reach the alveolar space by a normal diffusive process, and not as a result of epithelial membrane damage occurring at the time of lavage. Lung epithelial permeability to albumin in small, but finite (4.3--5.8 x 10(-10) cm/s). Virtually all (greater than 92%) of resistance to albumin flux across the alveolocapillary membrane lies in the epithelial barrier. Increases in permeability of the respiratory epithelium, even minor, would have a marked effect on water and solute balance in the lung. Epithelial injury will potentiate pulmonary edema formation even in the presence of normal pulmonary microvascular pressure, plasma oncotic pressure, and endothelial permeability.

Modulation of intracellular pH is widely implicated in the control of cell growth and metabolism, yet little is known about intracellular pH and brain function. To determine how stimulation of brain may affect the intracellular pH of mammalian glial cells, rat cortical astrocytes were studied for the first time in vivo using pH-sensitive electrodes of submicron caliber. Stimulation of the cortical surface caused a cytoplasmic alkaline shift of tenths of a pH within seconds. Cessation of induced electrical activity was followed by pH recovery and a small acid rebound. Recordings obtained during cortical-spreading depression revealed similar but generally larger intracellular pH shifts. Production of metabolic acids is known to occur when the brain is stimulated and has led to the long-held presumption that brain cells accordingly become more acidic. The observation that glia initially become more alkaline during electrical activity is thus paradoxical. The correlation of glial alkalinization with evoked electrical activity suggests that modulation of intracellular pH of glia may have important functional implications.

To investigate the influence of [Na+] in sweat on the distribution of body water during dehydration, we studied 10 volunteer subjects who exercised (40% of maximal aerobic power) in the heat [36 degrees C, less than 30% relative humidity (rh)] for 90-110 min to produce a dehydration of 2.3% body wt (delta TW). After dehydration, the subjects rested for 1 h in a thermoneutral environment (28 degrees C, less than 30% rh), after which time the changes in the body fluid compartments were assessed. We measured plasma volume, plasma osmolality, and [Na+], [K+], and [Cl-] in plasma, together with sweat and urine volumes and their ionic concentrations before and after dehydration. The change in the extracellular fluid space (delta ECF) was estimated from chloride distribution and the change in the intracellular fluid space (delta ICF) was calculated by subtracting delta ECF from delta TW. The decrease in the ICF space was correlated with the increase in plasma osmolality (r = -0.74, P less than 0.02). The increase in plasma osmolality was a function of the loss of free water (delta FW), estimated from the equation delta FW = delta TW - (loss of osmotically active substance in sweat and urine)/(control plasma osmolality) (r = -0.79, P less than 0.01). Free water loss, which is analogous to "free water clearance" in renal function, showed a strongly inverse correlation with [Na+] in sweat (r = -0.97, P less than 0.001). Fluid movement out of the ICF space attenuated the decrease in the ECF space.(ABSTRACT TRUNCATED AT 250 WORDS)

The intracellular contents of sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), and chloride (Cl-) in rat hindlimb muscles (soleus, plantaris, white and red gastrocnemii) were measured by instrumental neutron activation analysis (INAA) and atomic absorption spectrophotometry (AAS). Muscle extracellular fluid volume (ECFV) was determined using [3H]mannitol, [14C]mannitol, [3H]polyethylene glycol (PEG, mol wt 900, PEG-900) or the chloride (Cl) method and intracellular fluid volume (ICFV) calculated. Rats were anesthetized with pentobarbital sodium. The muscles were biopsied, frozen in liquid nitrogen, freeze-dried, weighed, and transferred to vials for analysis. For a given muscle, ion contents measured by the two methods showed a consistent small difference which could not be explained. The PEG-900 space and the Cl method yielded a larger ECFV than did mannitol; it is concluded that PEG-900 and Cl overestimate ECFV. There were significant differences in total tissue water (TTW), ECFV, ICFV, and intracellular ion contents between the different muscle types. The fast glycolytic muscles (white gastrocnemius, plantaris) had lower TTW (758 ml/kg wet wt) and ECFV (6.5-8.5% TTW) but the highest ICFV; the soleus (slow oxidative fibers) had the highest TTW (766 ml/kg wet wt) and ECFV (10-15% TTW) but the lowest ICFV. The fast-twitch white gastrocnemius and plantaris muscles have a higher intracellular content of K+ and lower Na+ and Cl- than the slow-twitch soleus muscle. The technique of INAA provides a rapid and accurate means of determining intramuscular ion content in small samples of tissue.

The catabolism of neurotensin (NT) was studied in the gastric submucosa of the conscious rat using a novel technique to obtain a dialysate of interstitial fluid. A microdialysis fiber system was surgically implanted into the gastric submucosa, and 2 days later experiments were commenced on conscious animals. Isotope-labeled NT was administered to the tissue, and a dialysate of the submucosal interstitial fluid was collected. In the dialysate, NT and catabolites of NT formed in the interstitial fluid were identified and quantitated by high-pressure liquid chromatography. The catabolism of 125I-NT-(1-13) and [3H]NT-(1-13) was studied as was the further breakdown of the major catabolites. NT-(1-13) was, regardless of the type of label, catabolized mainly into NT-(1-8), NT-(9-13), NT-(1-11), and free tyrosine. None of the catabolites formed is known to possess significant biological activity. NT-(9-13) was rapidly cleared, whereas the amino-terminal fragments NT-(1-8) and NT-(1-11) were more resistant to degradation. The biological half-life of neurotensin in the gastric submucosa of the rat was between 9 and 15 min.