Intraoperative muscle and fat metabolism in diabetic patients during coronary artery bypass grafting surgery: a parallel microdialysis and organ balance study.

BACKGROUND: Surgical trauma causes stress and inflammatory reactions with elevated serum free fatty acids (FFA) and glucose levels characteristic of intraoperative insulin resistance. Our aim was to compare microdialysis findings with those using the classical organ balance technique and to test the clinical feasibility of microdialysis during cardiac surgery. METHODS: Nine diabetic and nine non-diabetic patients, undergoing routine coronary artery bypass grafting surgery, were studied using both microdialysis and the organ balance technique in the brachio-radial muscle of the forearm, and microdialysis in the pre-pectoral fat tissue. Glucose, lactate, and glycerol were measured in arterial and venous plasma and in the microdialysate before administration of heparin, at the release of the aortic cross-clamp, and before transfer to the intensive care unit. RESULTS: Glucose release from the diabetic muscle at the last sampling time was detected. This was confirmed by a negative glucose A-I (arterial-interstitial difference) in the muscle. No differences were observed regarding lipolysis in the fat tissue in terms of A-I of glycerol. Intergroup differences were detected at the first sampling time, where arterial plasma glucose and plasma insulin levels were higher and muscle interstitial glucose lower in the diabetic patients. Plasma insulin was higher in the diabetic patients even at the final measurement time. CONCLUSIONS: In terms of lipolysis in the fat tissue and glucose transport in the muscle, the non-diabetic patients were metabolically 'diabetics' during surgery. Despite strict blood glucose control, disturbances in glucose homeostasis in the diabetic muscle persist. Microdialysis was easy to use during cardiac surgery.

Innervation of airway smooth muscle. Efferent mechanisms.

The classical view, with one excitatory (cholinergic) and one inhibitory (noradrenergic) component, of the innervation of airway smooth muscle is incomplete and at least two other, possibly peptidergic, types of innervation must be included when the innervation of airways is considered. A summary of these neuronal components is given in Fig. 1 and their possible origin is outlined. Besides the inhibitory noradrenergic innervation of the airways observed in some species, an inhibitory NANC (i-NANC) innervation has been demonstrated. The polypeptide, VIP, seems to be the most likely candidate for the neurotransmitter in the i-NANC innervation of the airways. The excitatory cholinergic innervation is present in the airways from the trachea down to the peripheral bronchi. In the guinea-pig bronchi an excitatory NANC (e-NANC) innervation has been demonstrated as well. The e-NANC nerves may correspond to chemosensitive primary afferent nerves with substance P or a related tachykinin as transmitter. When the innervation of airway smooth muscle of different mammalian species is compared it is evident that all nerve components except the cholinergic, show a considerable variability among species. The cholinergic innervation seems to be present in all mammalian species whereas the other components may be completely absent from some species. Distinct regional variations in the innervation of the airways may occur, which is exemplified by the distribution of the autonomic innervation in the guinea-pig tracheo-bronchial tree. Cholinergic neurotransmission in for example the guinea-pig and human airways can be modulated by NA via prejunctional inhibitory alpha 2-adrenoceptors. Furthermore, the e-NANC neurotransmission in the guinea-pig airways may be modulated by NA or by selective alpha 2-adrenoceptor agonists, acting via prejunctional inhibitory alpha 2-adrenoceptors. The clinical importance of the NANC innervation in relation to asthma is discussed. The i-NANC nerves may exert a modulating effect on bronchoconstriction, and a functional defect would presumably lead to an exaggerated response to constrictor stimuli. The e-NANC nerves in the airways may also be clinically relevant since the transmitter (tachykinins) from these nerves can produce bronchoconstriction and promote inflammation of the airway epithelium, either by direct mechanisms or indirectly by activation of mast cells, and thus contribute to the features of asthma.(ABSTRACT TRUNCATED AT 400 WORDS)

beta-Adrenoceptor-adenosine 3',5-monophosphate system in human leucocytes before and after treatment for hyperthyroidism.

Modifications in characteristics of the beta-adrenoceptor-cAMP system were observed in leucocytes from 10 patients in the hyperthyroid state after antithyroid treatment. These include 1) an increased number of beta-adrenoceptors without a change in their affinity, 2) an increased magnitude of stimulation of adenylate cyclase by isoprenaline, without a change in the NaF-stimulated enzyme activity, 3) an increased cAMP-dependent protein kinase activity ratio, and 4) an increased activity of cAMP-phosphodiesterase. Moreover, the plasma cAMP levels were markedly elevated during the hyperthyroid state. It is suggested that the above changes may in part constitute the molecular basis for the reputed catecholamine supersensitivity in the hyperthyroid state.

Modulation of P-selectin expression on isolated human platelets by an NO donor assessed by a novel ELISA application.

Adhesion molecules such as P-selectin are potential markers for evaluating platelet activation and studying the role of cell-cell interactions in numerous biological processes related to hemostasis and inflammation. The expression of P-selectin and related molecules has previously been quantified with different techniques. As an alternative to the most common method. flow cytometry, we have developed a useful ELISA method to simultaneously analyse 96 samples for platelet expression of P-selectin. Samples may be stored for at least 7 days at 4 degrees C prior to analysis. The method is simple, reproducible, flexible and requires only standard equipment. Washed platelets (WP) from healthy male volunteers, at a concentration of 1 x 10(7)/microtiter plate well, were stimulated with various known platelet activators and fixed with 0.1% formaldehyde for 10 min. The fixed WP were centrifuged to form a confluent layer in the wells and then incubated with optimal dilutions of primary antibodies (1/2000) directed against P-selectin, CD41, CD9 and secondary antibodies conjugated with alkaline phosphatase. Our results show that P-selectin expression on WP increases significantly upon stimulation with thrombin (0.1-1.0 U/ml), ADP (10 microM) and epinephrine (100 microM). The induction of P-selectin expression by thrombin is fast and has different kinetics depending on the concentration of the agonist. Prior incubation with the nitric oxide donor SNAP (10 microM) inhibits the up-regulation of P-selectin induced by sub-maximal concentrations of thrombin (p < 0.05). This ELISA is suitable for studying the expression and regulation of P-selectin and other surface molecules on human platelets in various pathological states.

Neurokinin A-LI release after antigen challenge in guinea-pig bronchial tubes: influence of histamine and bradykinin.

1. Our aim was to determine if antigen challenge stimulates sensory nerves and provokes the release of tachykinins. The involvement of histamine and bradykinin was studied by using specific receptor antagonists. Capsaicin-induced responses were also examined. Experiments were performed in vitro on tracheal and bronchial preparations from ovalbumin-sensitized guinea-pigs. 2. Characterization of ovalbumin-induced contraction, with regard to histamine and bradykinin, was carried out on airway ring preparations in the presence of phosphoramidon. The histamine H1 receptor antagonist pyrilamine reduced allergen-induced bronchial contractions by about 30%, whereas the bradykinin B2 receptor antagonist icatibant (Hoe 140) did not significantly affect the response. Combined treatment with pyrilamine (1 microM) and icatibant (0.1 microM) reduced the contractions by about 80%, indicating a synergistic inhibitory action. Tracheal preparations were not significantly affected by treatments, neither were capsaicin-induced contractions. 3. To study the outflow of tachykinins, we used a perfused bronchial-tube preparation, allowing simultaneous measurement of smooth muscle tension and mediator release. Neurokinin A-like immunoreactivity (NKA-LI) and substance P-like immunoreactivity (SP-LI) were determined by radioimmunoassay. 4. The results of the perfusion study showed an increased outflow of NKA-LI into the perfusate in response to ovalbumin (127% of basal) challenge. SP-LI determined in some of the samples showed a much lower amount (40 to 70 times lower) of SP-LI than NKA-LI. Treatment with icatibant and pyrilamine, separately and in combination, significantly reduced the ovalbumin-induced NKA-LI outflow by 38%, 26% and 22%, respectively. 5. Capsaicin-induced outflow (124% of basal) was not significantly affected by treatments (icatibant 121%, pyrilamine 107% and combined treatment 111% of basal). However, when pyrilamine was present the increased outflow was not statistically significant. 6. In conclusion, we found that allergen provocation of guinea-pig bronchi caused an increased outflow of NKA-LI that was reduced by treatment with both pyrilamine and icatibant. These findings demonstrate that the allergen-induced release of histamine and bradykinin stimulate sensory nerves and thereby increase outflow of tachykinins that contribute to the allergic reaction.

Characterization of pigment aggregating alpha 2-adrenoceptors of fish melanophores by use of different agonists after partial irreversible receptor inactivation.

1. The affinity for, and the intrinsic efficacy on, postsynaptic melanosome aggregating alpha 2-adrenoceptors of fish melanophores was studied for B-HT 920, clonidine, medetomidine, noradrenaline, phenylephrine and UK-14,304. Investigations were carried out by evaluating the effects of progressive, irreversible inactivation of the alpha 2-adrenoceptors by benextramine. 2. The double reciprocal plots of equieffective concentrations of B-HT 920, clonidine, noradrenaline and phenylephrine were linear, which indicated that these compounds exerted their effects, mainly, through interaction with one receptor site. 3. The affinity for the alpha 2-adrenoceptor selective agonist B-HT 920, was found to be about 1000 times higher than the affinity for the alpha 1-adrenoceptor selective agonist phenylephrine. 4. The corresponding plot of equieffective concentrations of medetomidine was not linear, which may indicate that this imidazole compound exerted its effect through more than one receptor site. However, when phenoxybenzamine was used in place of the more selective benextramine, a linear relationship was obtained.

Synergistic inhibition of thrombin-induced platelet aggregation by the novel nitric oxide-donor GEA 3175 and adenosine.

1. The influence of the novel nitric oxide-donor GEA 3175 on thrombin- and ionomycin-stimulated human platelets was investigated. The effect of GEA 3175 was compared with that of adenosine, an activator of platelet adenylyl cyclase. 2. GEA 3175 inhibited thrombin-induced secretion of ATP but did not affect aggregation; similar results were obtained with adenosine. 3. Thrombin-stimulated rises in the cytosolic free Ca2+ concentration, [Ca2+]i, were dose-dependently inhibited by GEA 3175 and adenosine. GEA 3175 and adenosine maximally reduced the initial rise in [Ca2+]i by 41% and 35%, respectively. 4. Simultaneous exposure to GEA 3175 and adenosine nearly abolished both the functional responses (i.e. aggregation and degranulation) and the rises in [Ca2+]i in thrombin-stimulated platelets. 5. Aggregation and increases in [Ca2+]i triggered in platelets by the Ca(2+)-ionophore ionomycin were only marginally affected by a combination of GEA 3175 and adenosine. 6. GEA 3175 potently increased the guanosine 3':5'-cyclic monophosphate (cyclic GMP) content in platelets but did not affect adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels. Adenosine did not increase either the cyclic AMP or the cyclic GMP levels in platelets. However, adenosine and GEA 3175 combined significantly elevated the platelet cyclic AMP content. 7. The results show that simultaneous exposure to GEA 3175 and adenosine promotes potent anti-aggregatory properties in platelets in vitro. The findings suggest that blockage of the cytosolic Ca(2+)-signal, which is probably mediated by an amplified cyclic nucleotide response, is an important event during the synergistic inhibition of thrombin-induced aggregation.

Suppression by neuropeptide Y of capsaicin-sensitive sensory nerve-mediated contraction in guinea-pig airways.

1. In the present study we have examined whether neuropeptide Y (NPY) interferes with non-adrenergic, non-cholinergic nerve-mediated contractions and relaxations in the guinea-pig airways. In these experiments we have used ring preparations of bronchi and trachea, incubated in the presence of atropine, propranolol and indomethacin (each 1 microM). 2. The contractile response to electrical stimulation of non-adrenergic, non-cholinergic nerve fibres was suppressed by NPY and NPY 13-36 in a concentration-dependent manner, these agents having similar inhibitory potencies. NPY caused a more complete inhibition than the C terminal fragment. 3. NPY affected neither the basal tension nor the substance P-evoked contraction in the bronchi and trachea and did not interfere with nerve-mediated, non-adrenergic relaxation in the trachea. 4. On the basis of these results, it is suggested that NPY may act on the terminals of sensory neurones in the airways to prevent antidromic, excitatory neurotransmission by inhibiting transmitter release.

Enalaprilat, but not cilazaprilat, increases inflammatory skin reactions in guinea-pigs.

The inflammatory effects of enalaprilat and cilazaprilat were tested in an experimental model of ovalbumin-sensitised guinea-pigs. Enalaprilat, but not cilazaprilat, enhanced the ovalbumin-induced inflammatory skin responses. The effect of enalaprilat was dose-dependent. Enalaprilat significantly increased the skin content of substance P and histamine. Cilazaprilat did not alter the level of these inflammatory mediators. Enalaprilat, applied locally, but not cilazaprilat, enhanced the inflammatory reactions caused by intradermal injections of allergen and substance P. Both angiotensin converting enzyme (ACE) inhibitors enhanced the inflammatory skin response evoked by bradykinin. Our study strongly indicates that enalaprilat has pro-inflammatory properties, whereas the new long-acting ACE inhibitor cilazaprilat does not. This might give a better safety profile of cilazaprilat.

Increased bronchial reactivity and potentiated skin responses in hypertensive subjects suffering from coughs during ACE-inhibitor therapy.

The aim of this study was to investigate whether ACE-inhibitors could influence bronchial reactivity and interfere with inflammatory skin responses. Ten hypertensive subjects, who had reacted with coughs during ACE-inhibitor therapy, were treated in a double-blind crossover fashion for two weeks with enalapril and with placebo. Enalapril reduced the PC20 value for histamine and augmented the dermal response. Circulating eosinophilic leukocyte level in venous blood dropped markedly after the histamine bronchoprovocation performed during enalapril treatment. Plasma substance P was reduced after histamine provocation performed during placebo treatment, whereas this reduction was abolished by enalapril. In this study, we have demonstrated ACE-inhibitor-induction of moderately increased bronchial reactivity in subjects with suspected ACE-inhibitor-elicited coughs. It is suggested that coughing during ACE-inhibitor therapy is due to an increased inflammatory state in the airways.

Epithelial modulation of allergen and drug effects in guinea pig airways.

The effect of egg albumin (EA) challenge on tracheal tube preparations from sensitized guinea pigs was studied with regard to EA permeability, histamine release and penetrability, and the contractile response of the preparation. We used a plethysmographic method that allowed simultaneous measurement of changes in smooth muscle tension and collection of samples for determination of mediators. Our results clearly show that epithelial damage potentiates the contractile response to histamine, potassium ions, and acetylcholine. Epithelial damage did not alter the maximal contractile response in preparations challenged with high antigen concentrations (EA, 1 mg/ml), but histamine release measured in the perfusate increased substantially. The permeability of the preparations to EA was greater when the epithelium was damaged. No increase in the permeability in response to the EA challenge was observed. The present study has demonstrated that guinea pig airway epithelium constitutes a barrier for both antigen and drugs. We also present a method for recording contractile responses from intact whole tracheal preparations, in which the epithelium can still act as a barrier, as is the case in vivo.

The melanophore aggregating response of isolated fish scales: a very rapid and sensitive diagnosis of whooping cough.

Pertussis toxin (PT) has been found to block noradrenaline-induced pigment aggregation in fish melanophores, and, based on this, a rapid and highly sensitive assay for PT was developed. Some preliminary results have also indicated that it may be possible to detect PT-like activity in saliva samples from patients with clinically suspected pertussis. In the present study the diagnostic value of the fish melanophore method was evaluated in 70 patients suspected of having pertussis; culture, serology and physician diagnosis were used as reference methods. In 60 of the patients, pertussis was verified by at least one of the reference methods. The melanophore test showed PT-like activity in saliva samples from 58 of the patients. Three patients with reference-verified pertussis showed no PT-like activity in the test; among these, one patient had been immunized and had also been treated with erythromycin during 3 days immediately prior to visiting the hospital. The melanophore test has three major advantages: it allows detection of pertussis in the early and curable stage of the disease; it takes only 2 h to perform; and it requires no sophisticated equipment.

Fish scales as biosensors for catecholamines.

Certain fish scales contain specialized cells (chromatophores) with pigment granulas, which can be dispersed or aggregated in the cells. The degree of aggregation is determined by a transmitter substance, noradrenaline, released by the sympathetic nerve endings in the skin. Isolated scales from, for example, cuckoo wrasse (Labrus ossifagus) retain a large sensitivity to externally applied noradrenaline (or more generally catecholamines) for several weeks. The degree of aggregation in isolated scales can be measured objectively by simple photometric techniques. We demonstrate in this paper how fish scales can be used to monitor catecholamine levels in human blood plasma. A discussion of other potential biosensor applications of this intact biological receptor-effector system is also given.

Nitric oxide modulates captopril-mediated angiotensin-converting enzyme inhibition in porcine iliac arteries.

The influence of the angiotensin-converting enzyme inhibitor captopril on bradykinin-and angiotensin I-induced responses with special regard to nitric oxide (NO) was studied. Auxometric tension and angiotensin-converting enzyme activity was studied in isolated porcine iliac arteries. Captopril potentiated bradykinin-induced contraction of preparations with intact endothelium; this potentiation was not seen with the kininase I inhibitor mergepta or a bradykinin B(1)-receptor antagonist. Captopril did not affect bradykinin-induced relaxation. The captopril-mediated increase of bradykinin-induced contraction was only seen in preparations with intact endothelium, while captopril did not affect arterial strips treated with Nomega-nitro-L-arginine. Angiotensin I-induced contractions was less reduced by captopril when the strips were pretreated with Nomega-nitro-L-arginine. Both captopril and the NO donor S-nitroso-N-acetyl-penicillamine inhibited angiotensin-converting enzyme activity. An additional reduction in angiotensin-converting enzyme activity was seen when S-nitroso-N-acetyl-penicillamine was added to captopril-treated preparations. In conclusion, captopril increased bradykinin-induced contraction in a NO-dependent manner. This potentiation is probably mediated by the increased metabolism of bradykinin by kininase I, and the additive angiotensin-converting enzyme inhibitory effect of captopril and NO.

The cyclic AMP system in sensitized and desensitized guinea-pig tracheal smooth muscle.

Egg albumin decreased the cyclic AMP content and the protein kinase ratio of sensitized guinea-pig tracheal smooth muscle. The effect preceded the contraction of the tracheal preparation. Antigen challenge increased cyclic AMP phosphodiesterase activity without changing the Km value. In tracheal preparations of desensitized guinea-pigs, the mechanical and metabolic effects of egg albumin were markedly reduced. These results suggest that the effects on the cyclic AMP system in response to immunological challenge might represent an important mechanism modulating the contractile response of guinea-pig tracheal smooth muscle.

Melatonin together with noradrenaline augments contractions of human myometrium.

The hormone melatonin is known to influence the circadian rhythm, and it probably also mediates some of the physiological changes that occur in the body at night. Inasmuch as uterine activity is greater during darkness, we investigated whether melatonin could modulate uterine contractility. Biopsies were performed during caesarean sections to obtain uterine tissue from women who had reached full term. The obtained samples were mounted in organ baths, and spontaneous contractions were recorded. Melatonin alone did not change myometrial contractility, whereas melatonin in combination with noradrenaline potentiated contractions. These results may indicate that melatonin plays a role in the timing of labour, since labour often begins late in the evening.

Effects of the nitric oxide-donor, GEA 3175, on guinea-pig airways.

This investigation characterized the smooth muscle relaxing effect of a novel nitric oxide (NO)-releasing substance, GEA 3175 (1,2,3,4-oxatriazolium, 3-(3-chloro-2-methylphenyl)-5-[[(4-methylphenyl)sulfonyl]amino], hydroxide inner salt) on guinea-pig trachea. GEA 3175 caused a concentration-dependent relaxation of tracheal smooth muscle precontracted with acetylcholine. This effect was reversed by both okadaic acid, an inhibitor of serine/threonine-specific phosphatases, and iberiotoxin, an inhibitor of Ca2+-activated K+ channels. Furthermore, GEA 3175 had a relaxation potency similar to that of the commonly used NO-donor, S-nitroso-N-acetyl-penicillamine. On the contractile response provoked by electrical field stimulation, GEA 3175 induced a long-lasting relaxation which persisted even after repeated washing. The relaxing effect of GEA 3175 was associated with rises in guanosine 3':5'-cyclic monophosphate (cGMP). In time course studies, cGMP continued to increase with incubation time after stimulation with GEA 3175 and there was a significant elevation of cGMP even after washing. In contrast, incubation with S-nitroso-N-acetyl-penicillamine caused a transient rise in cGMP. The present investigation showed that GEA 3175 evokes long-lasting effects on contractile responses and cGMP levels in guinea-pig trachea. Our results indicate that the relaxing effect of GEA 3175 occurs through a mechanism involving phosphatases and iberiotoxin-sensitive K+ channels.

Potentiation of inflammatory reactions in guinea-pig skin by an angiotensin converting enzyme inhibitor (MK 422).

There have recently been reports of persistent cough and increased broncho-obstruction likely to have been induced by ACE inhibitors. In order to study the effect of MK 422 (the active parent diacid of enalapril) on the inflammatory response, ovalbumin-sensitized guinea-pigs were tested intradermally with ovalbumin, capsaicin and bradykinin. All inflammatory responses were enhanced by treatment with MK 422 for 2 days prior to testing as compared to the responses of control animals. Infiltration of neutrophils, eosinophils, basophils and monocytes was increased following ovalbumin challenge in the MK 422-treated animals. We suggest that skin reactions and airway symptoms noticed during ACE inhibitor therapy might have been due to induced or potentiated inflammatory reactions in the skin or in the bronchial wall.

Inhibitory effects of clonidine on bronchospasm induced in guinea-pigs by vagal stimulation or antigen challenge.

The effects of clonidine on the bronchospastic responses induced by vagal stimulation or antigen challenge were studied in anaesthetized guinea-pigs. Electrical stimulation of the vagus nerves by 2-4 Hz induced a vigorous, mainly atropine-sensitive bronchoconstriction, which was strongly inhibited by clonidine (0.05 mg/kg i.v.). The inhibitory effect of clonidine was significantly reduced by the alpha 2-adrenoceptor antagonist yohimbine (1 mg/kg i.v.). Another series of experiments was done with ovalbumin-sensitized guinea-pigs. Respiratory anaphylaxis was induced by antigen inhalation resulting in an increase of pulmonary resistance from 100% (baseline) to about 190% in the control group. Animals pretreated with a clonidine aerosol (0.03%) showed a marked inhibition of the bronchospastic response. It is suggested that the inhibition of the bronchospastic responses induced by clonidine may be mediated by a stimulation of alpha 2-adrenoceptors, which exerts an inhibitory control of the excitatory vagal activity in the guinea-pig airways.

Inhibitory effects of clonidine on allergic reactions in guinea-pig skin.

An experimental guinea-pig model was used to show that clonidine inhibited dose dependently the wheal and flare reaction to i.d. ovalbumin in sensitized animals. The effect of clonidine was counteracted by an alpha 2-adrenoceptor antagonist, yohimbine, but not by an alpha 1-adrenoceptor antagonist, prazosin. An H1-receptor antagonist, clemastine, initially reduced the wheal and flare reaction but did not influence the effect of clonidine. Cimetidine, an H2-receptor antagonist slightly reduced the effect of clonidine on the wheal and flare reaction. It is suggested that clonidine reduces the wheal and flare reaction by stimulating alpha 2-adrenoceptors, which inhibits the axon reflex of the response.