Mucus Hydration in Subjects with Stable Chronic Bronchitis: A Comparison of Spontaneous and Induced Sputum.

Mucus hydration is important in mucus clearance and lung health. This study sought to test the relative utility of spontaneous sputum (SS) versus the reasonably noninvasive induced sputum (IS) samples for measurement of mucus hydration. SS and IS samples were collected over a 2-day study interval. Sputum was induced with escalating inhaled nebulized 3-5% hypertonic saline. Viscous portions of the samples ("plugs") were utilized for percent solids and total mucin analyses. Cytokines, nucleotides/nucleosides and cell differentials were measured in plugs diluted into 0.1% Sputolysin. Overall, 61.5% of chronic bronchitis (CB) subjects produced a SS sample and 95.2% an IS sample. Total expectorate sample weights were less for the SS (0.94 ± 0.98 g) than the IS (2.67 ± 2.33 g) samples. Percent solids for the SS samples (3.56% ± 1.95; n = 162) were significantly greater than the IS samples (3.08% ± 1.81; n = 121), p = 0.133. Total mucin concentrations also exhibited a dilution of the IS samples: SS = 4.15 ± 3.23 mg/ml (n = 62) versus IS= 3.34 ± 2.55 mg/ml (n = 71) (p = 0.371). Total mucins (combined SS and IS) but not percent solids, were inversely associated with FEV1 percent predicted (p = 0.052) and FEV1,/FVC % (p = 0.035). There were no significant differences between sample types in cytokine or differential cell counts. The probability of sample collections was less for SS than IS samples. Measurements of hydration revealed modest dilution of the IS samples compared to SS. Thus for measurements of mucus hydration, both SS and IS samples appear to be largely interchangeable.

Sodium transport inhibition by amiloride reduces basolateral membrane potassium conductance in tight epithelia.

In toad and frog urinary bladder, electrophysiological data suggest that inhibition of transepithelial sodium transport by mucosal amiloride results in a decrease in basolateral membrane conductance. These results were confirmed by showing that amiloride addition caused a decrease in basolateral membrane potassium permeability.

Bioconcentration factors for hydrocarbons and petrochemicals: Understanding processes, uncertainty and predictive model performance.

Fish bioconcentration factors (BCFs) are often used to assess substance-specific bioaccumulation. However, reliable BCF data are limited given the practical challenges of conducting such tests. The objectives of this paper are to describe nine rainbow trout studies performed in our lab using tailored dosing and test designs for obtaining empirical BCFs for 21 test substances; gain insights into the structural features and processes determining the magnitude and uncertainty in observed BCFs; and assess performance of six quantitative structure property relationships (QSPRs) for correctly categorizing bioaccumulation given current regulatory triggers. Resulting mean steady-state BCFs, adjusted to a 5% lipid content, ranged from 12 Lkg-1 for isodecanol to 15,448 Lkg-1 for hexachlorobenzene which served as a positive control. BCFs for hydrocarbons depended on aromatic and saturated ring configurations and position. Uptake clearances appeared to be modulated by gill metabolism and substance bioavailability, while elimination rates were likely influenced by somatic biotransformation. Current approaches for quantifying uncertainty in experimental BCFs, which take into account only variability in measured fish concentrations, were found to underestimate the true uncertainty in this endpoint with important implications for decision-making. The Vega (KNN/Read-Across) QSPR and Arnot-Gobas model yielded the best model performance when compared to measured BCFs generated in this study.

Selective response of human airway epithelia to luminal but not serosal solution hypertonicity. Possible role for proximal airway epithelia as an osmolality transducer.

The response of cultured human nasal epithelia to hypertonic bathing solutions was tested using ion-selective microelectrode and quantitative microscopy. Raised luminal, but not serosal, osmolality (+/- 150 mM mannitol) decreased Na+ absorption but did not induce Cl- secretion. Raised luminal osmolality increased cell Cl- activity, Na+ activity, and transepithelial resistance and decreased both apical and basolateral membrane potentials and the fractional resistance of the apical membrane; equivalent circuit analysis revealed increases in apical, basolateral, and shunt resistances. Prolonged exposure (10 min) to 430 mosM luminal solution elicited no regulation of any parameter. Optical measurements revealed a reduction in the thickness of preparations only in response to luminal hypertonic solutions. We conclude that (a) airway epithelial cells exhibit asymmetric water transport properties, with the apical membrane water permeability exceeding that of the basolateral membrane; (b) the cellular response to volume loss is a deactivation of the basolateral membrane K+ conductance and the apical membrane Cl- conductance; (c) luminal hypertonicity slows the rate of Na+ absorption but does not induce Cl- secretion; and (d) cell volume loss increases the resistance of the paracellular path. We speculate that these properties configure human nasal epithelium to behave as an osmotic sensor, transducing information about luminal solutions to the airway wall.

Osmotic water permeabilities of cultured, well-differentiated normal and cystic fibrosis airway epithelia.

Current hypotheses describing the function of normal airway surface liquid (ASL) in lung defense are divergent. One theory predicts that normal airways regulate ASL volume by modulating the flow of isosmotic fluid across the epithelium, whereas an alternative theory predicts that ASL is normally hyposmotic. These hypotheses predict different values for the osmotic water permeability (P(f)) of airway epithelia. We measured P(f) of cultures of normal and cystic fibrosis (CF) airway epithelia that, like the native tissue, contain columnar cells facing the lumen and basal cells that face a basement membrane. Xz laser scanning confocal microscopy recorded changes in epithelial height and transepithelial volume flow in response to anisosmotic challenges. With luminal hyperosmotic challenges, transepithelial and apical membrane P(f) are relatively high for both normal and CF airway epithelia, consistent with an isosmotic ASL. Simultaneous measurements of epithelial cell volume and transepithelial water flow revealed that airway columnar epithelial cells behave as osmometers whose volume is controlled by luminal osmolality. Basal cell volume did not change in these experiments. When the serosal side of the epithelium was challenged with hyperosmotic solutions, the basal cells shrank, whereas the lumen-facing columnar cells did not. We conclude that (a) normal and CF airway epithelia have relatively high water permeabilities, consistent with the isosmotic ASL theory, and the capacity to restore water on airway surfaces lost by evaporation, and (b) the columnar cell basolateral membrane and tight junctions limit transepithelial water flow in this tissue.

Coordinated clearance of periciliary liquid and mucus from airway surfaces.

Airway surface liquid is comprised of mucus and an underlying, watery periciliary liquid (PCL). In contrast to the well-described axial transport of mucus along airway surfaces via ciliary action, theoretical analyses predict that the PCL is nearly stationary. Conventional and confocal microscopy of fluorescent microspheres and photoactivated fluorescent dyes were used with well-differentiated human tracheobronchial epithelial cell cultures exhibiting spontaneous, radial mucociliary transport to study the movements of mucus and PCL. These studies showed that the entire PCL is transported at approximately the same rate as mucus, 39.2+/-4.7 and 39.8+/-4.2 micrometer/sec, respectively. Removing the mucus layer reduced PCL transport by > 80%, to 4.8+/-0.6 micrometer/sec, a value close to that predicted from theoretical analyses of the ciliary beat cycle. Hence, the rapid movement of PCL is dependent upon the transport of mucus. Mucus-dependent PCL transport was spatially uniform and exceeded the rate expected for pure frictional coupling with the overlying mucus layer; hence, ciliary mixing most likely accelerates the diffusion of momentum from mucus into the PCL. The cephalad movement of PCL along airway epithelial surfaces makes this mucus-driven transport an important component of salt and water physiology in the lung in health and disease.

Assessment of selective inhibition of rat cerebral cortical calcium-independent and calcium-dependent phosphodiesterases in crude extracts using deoxycyclic AMP and potassium ions.

The effects of various inhibitors on the activity of calcium-independent and calcium-dependent phosphodiesterases from rat cerebral cortex were examined. While the agents varied greatly in their relative potency, each was found to be approximately equipotent in inhibiting the calcium-dependent hydrolysis of either cyclic AMP or cyclic GMP. In contrast, the inhibitors displayed a marked substrate specificity for the calcium-independent enzyme with ratios of IC50 values for inhibition of cyclic GMP hydrolysis when compared to cyclic AMP hydrolysis in decreasing order being: ZK 62711 (much greater than 100) greater than Ro 20-1724 (much greater than 25) papaverine (13) greater than 7-benzyl IBMX (4) greater than quercetin and kaempferol (2). The differential selectivity of the inhibitors for the two enzymes was most pronounced for ZK 62711 and Ro 20-1724 which were at least 25-100-times more potent in inhibiting the calcium-independent hydrolysis of cyclic AMP when compared to the calcium-dependent hydrolysis of cyclic AMP. In contrast, 7-benzyl IBMX, kaempferol and quercetin were 8-100-times more effective as inhibitors of cyclic GMP hydrolysis by the calcium-dependent phosphodiesterase while 7-benzyl IBMX and trimazosin displayed a similar enzyme selectivity using cyclic AMP as substrate. With the exception of papaverine, all agents were competitive inhibitors of the calcium-dependent phosphodiesterase. The type of inhibition observed with the calcium-independent enzyme was dependent on the substrate employed. The specificity of potassium ions in inhibiting the activity of the calcium-dependent phosphodiesterase and deoxycyclic AMP in inhibiting the calcium-independent enzyme was found to provide a convenient means to assess the effects of agents on these activities in crude extracts of cerebral cortex.

Selective alteration of Ca2+-dependent and Ca2+-independent cyclic nucleotide phosphodiesterase activity in rat cerebral cortex by cyclic nucleotides and their analogs.

The effects of various cyclic nucleotides and cyclic nucleotide analogs on the activity of Ca2+-independent and Ca2+-dependent phosphodiesterases purified from rat cerebral cortex were examined. The order of potency for inhibition of the Ca2+-dependent enzyme by the various agents was the same using either cAMP or cGMP as substrate with 2'-O-monobutyryl cGMP, cIMP and 2-deoxy cGMP being the most potent. The inhibition of deoxy cGMP using cAMP or cGMP as substrate was competitive, with Ki values of 11 and 13 microM, respectively. In marked contrast, hydrolysis of cAMP or cGMp by the Ca2+-independent enzyme was stimulated 50-75% by cIMP, deoxy cGMP and N2-monobutyryl cGMP with EC50 values of 7, 20 and 30 microM, respectively. cGMP (EC50, 1.5 microM) produced quantitatively the same degree of stimulation of cAMP hydrolysis by the Ca2+-independent phosphodiesterase and the activation was not additive with that of deoxy cGMP. Of the other derivatives examined, 2'-O-monobutyryl cAMP and 2'-deoxy cAMP were the most potent inhibitors of cAMP hydrolysis by the Ca2+-independent enzyme and were 30-60 times more effective in inhibiting cAMP hydrolysis as compared to cGMP hydrolysis. The specificity of K+ in inhibiting the activity of the Ca2+-dependent phosphodiesterase and deoxy cAMP in inhibiting the Ca2+-independent enzyme may provide convenient means to examine specifically these activities in crude extracts from rat cerebral cortex.

Ontogenetic changes in levels of phosphodiesterase for adenosine 3':5'-monophosphate and glucosine 3':5'-monophosphate in the lung, brain and heart from guinea pigs.

Changes in tissue levels of the low Km phosphodiesterase for adenosine 3':5'-monophosphate (cyclic AMP) and guanosine 3':5'-monophosphate (cyclc GMP) in the lung, liver, heart and brain from developing guinea pigs were studied. It was found that the contents of the soluble (cytosol) phosphodiesterase for both cyclic AMP and cyclic GMP were higher in the lung from the fetus than from the neonate and adult. The ontogenetic changes seen in the liver were qualitatively similar to thos in the lung with respect to cyclic GMP hydrolysis, while a reversed pattern of change was noted in the brain. The level of cyclic AMP phosphodiesterase was highest in the fetal heart. Throughout the fetal stage, the levels of the enzyme for cyclic GMP hydrolysis were higher than those for cyclic AMP in the lung. At or around birth, a reversal in the relative levels of the two enzymes took place; two days after birth, the level of the enzyme for cyclic AMP was 2-3times higher than thos for cyclic GMP. Kinetic analysis showed that phohphodiesterases from extracts of the lung from all developmental stages of guinea pigs had the same Km (2.6 muM) for cyclic AMP and the same Km (6.6 muM) for cyclic GMP. The relative values of V, based on assays using the same amount of enzyme protein, in decreasing order, were fetus greater than neonate greater than adult. The present findings suggest that metabolism of the two cyclic nucleotides may be closely related to developmental processes of the tissues. Moreover, the actions involving cyclic GMP may be more predominent in the fetal lung and adult brain.

Calcein accumulation as a fluorometric functional assay of the multidrug transporter.

Acetoxymethyl ester (AM) derivatives of various fluorescent indicators (fura-2, fluo-3, indo-1, BCECF, calcein) are actively extruded by the multidrug transporter (MDR1, P-glycoprotein-Homolya, L. et al. (1993) J. Biol. Chem. 268, 21493-21496). In the present paper we show that the measurement of the accumulation of a fluorescent cell viability marker, calcein, can be effectively used as a rapid and sensitive fluorometric and flow cytometric assay for studying P-glycoprotein function. The rate of calcein accumulation in human MDR1-expressing cells is significantly lower than in the control cells, while various drug-resistance reversing agents (verapamil, vinblastine, oligomycin, cyclosporin A and UIC2 monoclonal antibody) greatly increase calcein trapping only in the MDR1-expressing cells. Since calcein-AM is not fluorescent and free calcein is not a substrate of the multidrug transporter, the assay is readily applicable for rapid kinetic studies of the MDR1 function. Calcein has a high fluorescence intensity in the visible range, thus changes in calcein uptake can be easily visualised and MDR1-expressing and control cells separated by conventional flow cytometry.

Modified cyclic nucleotide systems in Morris hepatoma 3924A favoring expression of cyclic GMP effect.

Modifications in the cyclic nucleotide systems favoring the expression of cyclic GMP effects were found to occur in the transplanted fast-growing Morris hepatoma 3924A. These included: (a) a decreased level of cyclic GMP phosphodiesterase and an increased level of cyclic AMP phosphodiesterase; (b) a disproportionately increased level of cylic GMP-dependent protein kinase relative to that of cyclic AMP-dependent protein kinase; (c) a disproportionately increased level of stimulatory modulator of cyclic AMP-dependent protein kinase relative to that of inhibitory modulator of cyclic AMP-dependent protein kinase; and (d) an increased level of phosphoprotein phosphatase.

Cyclic GMP-dependent and cyclic AMP-dependent protein kinases, protein kinase modulators and phosphodiesterases in arteries and veins of dogs. Distribution and effects of arteriovenous fistula and arterial occlusion.

Possible involvement of cyclic GMP-dependent and cyclic AMP-dependent protein kinases, protein kinase modulators and cyclic nucleotide phosphodiesterases in functions of vascular tissues were investigated in the dog. All of the above activities, localized in the smooth muscle-rich inner layer of the blood vessels, were found to be higher in the arteries than in the veins. The peripheral arteries were disproportionately richer in cyclic GMP-dependent protein kinase (as indicated by high ratios of cyclic GMP-dependent to cyclic AMP-dependent protein kinase) than were the veins, with the exception of the pulmonary artery, an atypical arterial tissue exposed to low blood pressure. Interestingly, the protein kinase ratio for the aorta, an artery with no significant role in blood pressure regulation, was not higher than that for the vena cava. Creation of femoral arteriovenous fistulae in the dogs led to preferential reductions in the cyclic GMP-dependent enzyme activity both in the proximal and distal arteries, whereas it was elevated in the stressed vein distal to the anastomotic site. The cyclic GMP-dependent enzyme was preferentially reduced in the saphenous artery distal to occlusion. Changes in the cyclic GMP-dependent enzyme activity appeared to precede gross atrophy or hypertrophy of the vessels. It is suggested that the vascular cyclic GMP-dependent protein kinase may be closely related to peripheral resistance and its regulation.

Sodium transport effects on the basolateral membrane in toad urinary bladder.

In toad urinary bladder epithelium, inhibition of Na transport with amiloride causes a decrease in the apical (Vmc) and basolateral (Vcs) membrane potentials. In addition to increasing apical membrane resistance (Ra), amiloride also causes an increase in basolateral membrane resistance (Rb), with a time course such that Ra/Rb does not change for 1-2 min. At longer times after amiloride (3-4 min), Ra/Rb rises from its control values to its amiloride steady state values through a secondary decrease in Rb. Analysis of an equivalent electrical circuit of the epithelium shows that the depolarization of Vcs is due to a decrease in basolateral electromotive force (Vb). To see of the changes in Vcs and Rb are correlated with a decrease in Na transport, external current (Ie) was used to clamp Vmc to zero, and the effects of amiloride on the portion of Ie that takes the transcellular pathway were determined. In these studies, Vcs also depolarized, which suggests that the decrease in Vb was due to a decrease in the current output of a rheogenic Na pump. Thus, the basolateral membrane does not behave like an ohmic resistor. In contrast, when transport is inhibited during basolateral membrane voltage clamping, the apical membrane voltage changes are those predicted for a simple, passive (i.e., ohmic) element.

Interactions of sodium transport, cell volume, and calcium in frog urinary bladder.

The volume of individual cells in intact frog urinary bladders was determined by quantitative microscopy and changes in volume were used to monitor the movement of solute across the basolateral membrane. When exposed to a serosal hyposmotic solution, the cells swell as expected for an osmometer, but then regulate their volume back to near control in a process that involves the loss of KCl. We show here that volume regulation is abolished by Ba++, which suggests that KCl movements are mediated by conductive channels for both ions. Volume regulation is also inhibited by removing Ca++ from the serosal perfusate, which suggests that the channels are activated by this cation. Previously, amiloride was observed to inhibit volume regulation: in this study, amiloride-inhibited, hyposmotically swollen cells lost volume when the Ca++ ionophore A23187 was added to Ca++-replete media. We attempted to effect volume changes under isosmotic conditions by suddenly inhibiting Na+ entry across the apical membrane with amiloride, or Na+ exit across the basolateral membrane with ouabain. Neither of these Na+ transport inhibitors produced the expected results. Amiloride, instead of causing a decrease in cell volume, had no effect, and ouabain, instead of causing cell swelling, caused cell shrinkage. However, increasing cell Ca++ with A23187, in both the absence and presence of amiloride, caused cells to lose volume, and Ca++-free Ringer's solution (serosal perfusate only) caused ouabain-blocked cells to swell. Finally, again under isosmotic conditions, removal of Na+ from the serosal perfusate caused a loss of volume from cells exposed to amiloride. These results strongly suggest that intracellular Ca++ mediates cell volume regulation by exerting a negative control on apical membrane Na+ permeability and a positive control on basolateral membrane K+ permeability. They also are compatible with the existence of a basolateral Na+/Ca++ exchanger.

The relative roles of passive surface forces and active ion transport in the modulation of airway surface liquid volume and composition.

Two hypotheses have been proposed recently that offer different views on the role of airway surface liquid (ASL) in lung defense. The "compositional" hypothesis predicts that ASL [NaCl] is kept low (<50 mM) by passive forces to permit antimicrobial factors to act as a chemical defense. The "volume" hypothesis predicts that ASL volume (height) is regulated isotonically by active ion transport to maintain efficient mechanical mucus clearance as the primary form of lung defense. To compare these hypotheses, we searched for roles for: (1) passive forces (surface tension, ciliary tip capillarity, Donnan, and nonionic osmolytes) in the regulation of ASL composition; and (2) active ion transport in ASL volume regulation. In primary human tracheobronchial cultures, we found no evidence that a low [NaCl] ASL could be produced by passive forces, or that nonionic osmolytes contributed substantially to ASL osmolality. Instead, we found that active ion transport regulated ASL volume (height), and that feedback existed between the ASL and airway epithelia to govern the rate of ion transport and volume absorption. The mucus layer acted as a "reservoir" to buffer periciliary liquid layer height (7 microm) at a level optimal for mucus transport by donating or accepting liquid to or from the periciliary liquid layer, respectively. These data favor the active ion transport/volume model hypothesis to describe ASL physiology.

Axis II comorbidity in substance abusers.

OBJECTIVE: To assess the complex relationship between substance abuse and personality disorders, the authors determined the prevalence of personality disorders in a group of middle-class substance abusers and compared the subjects who had personality disorders with those who did not. METHOD: The subjects were drawn from patients consecutively admitted to an inpatient substance abuse program in a private psychiatric hospital; they were the first 100 who agreed to participate. Substance dependence was diagnosed according to DSM-III-R, and the patients were assessed with the Structured Clinical Interview for DSM-III-R Personality Disorders, Alcohol Use Inventory, MMPI, Health and Daily Living Form, Shipley Institute of Living Scale, and measures of chemical use and life satisfaction. RESULTS: Of the 100 substance abusers, 57 had personality disorders. These patients differed significantly from the 43 patients without personality disorders in several ways: they had greater involvement with illegal drugs, had different patterns of alcohol use, had greater psychopathology, were less satisfied with their lives, and were more impulsive, isolated, and depressed. CONCLUSIONS: Because of the marked differences between the substance abusers with and without personality disorders, a uniform approach to substance abuse treatment may be inadequate.

1-(4-Aminobenzyl)-and 1-(4-aminophenyl)isoquinoline derivatives: synthesis and evaluation as potential irreversible cyclic nucleotide phosphodiesterase inhibitors.

In an effort to increase the specificity of the potent phosphodiesterase inhibitor papaverine, we synthesized two series of novel 1-(4-aminobenzyl)- and 1-(4-aminophenyl)isoquinoline derivatives, incorporating alkylating moieties on the amine substituents. These compounds were evaluated for their inhibitory action on phosphodiesterase preparations from bovine heart and rat cerebral cortex. Studies were also conducted to determine whether these compounds were reacting with the enzymes in an irreversible manner. The compounds were potent inhibitors of the phosphodiesterases; however, no evidence was found for an irreversible inhibition.

1-(4-Aminophenyl)isoquinoline derivatives. Potent inhibitors of calcium-independent and calcium-dependent phosphodiesterases from rat cerebral cortex.

The effects of a series of 1-(4-aminophenyl)isoquinoline derivatives on the activity of calcium-independent and calcium-dependent phosphodiesterases purified from rat cerebral cortex were examined. Agents were approximately equipotent (IC50 values, 0.2 to 25 microM) in inhibiting the calcium-dependent hydrolysis of either cyclic AMP or cyclic GMP, while they were 6-35 times more effective as inhibitors of cyclic AMP hydrolysis when compared to cyclic GMP hydrolysis using the calcium-independent enzyme. The diastereomers of 3-(carbomethoxy)propenamido demonstrated a marked difference in specificity. The cis-isomer was very potent in inhibiting cyclic AMP or cyclic GMP hydrolysis by either enzyme (IC50 values, 0.2 to 8 microM) while the trans-isomer was only effective in inhibiting calcium-independent cyclic AMP hydrolysis (IC50 values, 2.5 microM). Kinetic analyses of the type of inhibition of the calcium-dependent enzyme revealed that the various agents were competitive inhibitors of cyclic GMP hydrolysis and noncompetitive inhibitors of cyclic AMP hydrolysis. A reverse pattern of inhibition by the isoquinoline derivatives was found using the calcium-independent phosphodiesterase, i.e. noncompetitive inhibition of cyclic GMP while competitive inhibition of cyclic AMP. Inhibition of phosphodiesterases by these agents was also manifest using intact brain slices prepared from rat cerebral cortex. Thus, the agents were found to potentiate forskolin-elicited accumulations of cyclic AMP by 100-700% and increased the half-time for the decline in cyclic AMP following forskolin stimulation from 3 to 6 min.

Effects of cholinergic drugs on longitudinal contraction in levamisole-susceptible and -resistant Haemonchus contortus.

A novel force transducer was used to measure the effects of cholinergic agonists on longitudinal contraction in Haemonchus contortus. Drugs were applied to whole worms or injected via a cannula in the pseudocoelomic cavity. A number of agonists, including nicotine and the anthelmintics m-aminolevamisole, levamisole and morantel, caused contractions in whole worms. Four- to 25-fold increases in concentration of the active compounds were required to cause contractions in each of two levamisole-resistant strains of H. contortus. Of the other compounds tested, bephenium had equivalent activity against susceptible and resistant strains. Anticholinesterase compounds caused contractions after a slight delay in susceptible, but not resistant worms. Numerous cholinergic agonists and other compounds did not cause contraction when applied to whole worms. One of these, acetylcholine, caused contractions in cannulated worms. Compared with the susceptible strain, five- to six-fold higher concentrations of acetylcholine were required to cause equivalent contractions in the resistant strains. Levamisole resistance in adult H. contortus is likely to be due to a change in the characteristics of the cholinergic receptor(s).

Regulation of adenosine 3':5'-monophosphate-dependent protein kinase in cerebral cortex.

Alterations in the cyclic AMP-dependent protein kinase activity ratio in response to putative neurotransmitters and other cyclic AMP-elevating agents in intact cerebral cortical slices and Krebs-Ringer particulate preparations from cerebral cortex were examined. Both norepinephrine (30 microM) and forskolin (20 microM) produced a time-dependent increase in intracellular levels of cyclic AMP in cerebral cortical slices which was paralleled by an increase in both cyclic AMP and the protein kinase activity ratio. The increases were maximal at 5 min. and remained elevated for at least 15 min. Forskolin, norepinephrine, adenosine and isoproterenol produced a concentration-dependent increase in both cyclic AMP and the protein kinase activity ratio, however, the degree of increase observed was dissimilar. Thus, a 5-fold change in intracellular cyclic AMP resulted in only a 2-fold increase in the activity ratio. Of the agents examined, forskolin produced the most marked change in the activity ratio (from 0.23 to 0.78 at 100 microM) while isoproterenol at 100 microM produced only a 50% increase in the activity ratio. The half-time for the decline in forskolin elicited elevations of either the activity ratio or cyclic AMP was about 4-6 min. In the presence of the phosphodiesterase inhibitor, Ro 20-1724, both were significantly prolonged being 60-70% of the maximum observed immediately after forskolin stimulation, at 15 min. Potentiation of forskolin elicited increases in the activity ratio by Ro 20-1724 were also observed but the increase in the activity ratio was maximal at 7.5 min. while cyclic AMP accumulations continued to rise during the entire 15 min. incubation. Particulate preparations from cerebral cortex were found to contain a cyclic AMP-dependent protein kinase which could be activated 2 to 3-fold with either forskolin, norepinephrine, or adenosine. Unlike the intact brain slice the changes in protein kinase activity ratio and intracellular levels of cyclic AMP in cell-free particulate preparations were similar in both time and degree.