Disturbed spermatogenic signaling in pituitary adenylate cyclase activating polypeptide-deficient mice.

PACAP is a neuropeptide with diverse functions in various organs, including reproductive system. It is present in the testis in high concentrations, and in addition to the stage-specific expression within the seminiferous tubules, PACAP affects spermatogenesis and the functions of Leydig and Sertoli cells. Mice lacking endogenous PACAP show reduced fertility, but the possibility of abnormalities in spermatogenic signaling has not yet been investigated. Therefore, we performed a detailed morphological analysis of spermatozoa, sperm motility and investigated signaling pathways that play a role during spermatogenesis in knockout mice. No significant alterations were found in testicular morphology or motility of sperm in homozygous and heterozygous PACAP-deficient mice in spite of the moderately increased number of severely damaged sperms. However, we found robust changes in mRNA and/or protein expression of several factors that play an important role in spermatogenesis. Protein kinase A expression was markedly reduced, while downstream phospho-ERK and p38 were elevated in knockout animals. Expression of major transcription factors, such as Sox9 and phospho-Sox9, was decreased, while that of Sox10, as a redundant factor, was increased in PACAP-deficient mice. The reduced phospho-Sox9 expression was partly due to increased expression and activity of phosphatase PP2A in knockout mice. Targets of Sox transcription factors, such as collagen type IV, were reduced in knockout mice. In summary, our results show that lack of PACAP leads to disturbed signaling in spermatogenesis, which could be a factor responsible for reduced fertility in PACAP knockout mice, and further support the role of PACAP in reproduction.

Cardiorespiratory fitness in a representative sample of Belgian firefighters.

BACKGROUND: An important aspect of occupational health surveillance of firefighters is cardiorespiratory fitness. In Belgium, representative data on firefighters' cardiorespiratory fitness assessed in a standardized way are lacking. AIMS: To report data on cardiorespiratory fitness, body mass index (BMI) and total body fat percentage in a large cohort of Belgian firefighters; to relate the data on cardiorespiratory fitness to the new Belgian criteria and to explore the relationship of cardiorespiratory fitness with age, BMI and total body fat. METHODS: VO2-max was assessed in male firefighters by maximal exercise test on a treadmill. Total body fat percentage was assessed by dual-energy X-ray absorptiometry. Stratified analyses of mean VO2-max and proportions of subjects that did not meet the criteria were performed for different age, total body fat percentage and BMI categories. Relationships between VO2-max and the continuous variables were explored in univariate (correlation coefficients) and multivariate analyses (multiple linear regression analysis). RESULTS: In 1225 participating firefighters (96% participation rate), mean VO2-max was 46.5 ml/kg/min. Percentages of subjects that did not meet the criteria ranged from 1 to 83% depending on age, BMI and total body fat percentage. Both in univariate and multivariate analyses, strongly significant relationships were found between VO2-max and age, BMI and total body fat percentage, the latter being the strongest predictor. CONCLUSIONS: The study provided representative data on cardiorespiratory fitness, BMI and total body fat percentage for Belgian firefighters. The findings suggest the need for a structural approach on healthy eating and regular physical exercise in firefighters.

The effects of pituitary adenylate cyclase activating polypeptide in renal ischemia/reperfusion.

Pituitary adenylate cyclase activating polypeptide (PACAP ) is a multifunctional neuropeptide occurring in the nervous system as well as in the peripheral organs. Beneficial action of PACAP has been shown in different pathological processes. The strong protective effects of the peptide are probably due to its complex modulatory actions in antiapoptotic, anti-inflammatory and antioxidant pathways. In the kidney, PACAP is protective in models of diabetic nephropathy, myeloma kidney injury, cisplatin-, gentamycin- and cyclosporin-induced damages. Numerous studies have been published describing the protective effect of this peptide in renal ischemia/reperfusion. The present review focuses on the ischemia/reperfusion-induced kidney injury and gives a brief summary about the results published in this area.

White plague among the "forgotten people" from the Barbaricum of the Carpathian Basin-Cases with tuberculosis from the Sarmatian-period (3rd-4th centuries CE) archaeological site of Hódmezovásárhely-Kenyere-ér, Bereczki-tanya (Hungary).

Tuberculosis (TB) is a bacterial infection that is well-known in the palaeopathological record because it can affect the skeleton and consequently leaves readily identifiable macroscopic alterations. Palaeopathological case studies provide invaluable information about the spatio-temporal distribution of TB in the past. This is true for those archaeological periods and geographical regions from when and where no or very few TB cases have been published until now-as in the Sarmatian period (1st-5th centuries CE) in the Barbaricum of the Carpathian Basin. The aim of our paper is to discuss five newly discovered TB cases (HK199, HK201, HK225, HK253, and HK309) from the Sarmatian-period archaeological site of Hódmezovásárhely-Kenyere-ér, Bereczki-tanya (Csongrád-Csanád county, Hungary). Detailed macromorphological evaluation of the skeletons focused on the detection of bony changes likely associated with different forms of TB. In all five cases, the presence of endocranial alterations (especially TB-specific granular impressions) suggests that these individuals suffered from TB meningitis. Furthermore, the skeletal lesions observed in the spine and both hip joints of HK225 indicate that this juvenile also had multifocal osteoarticular TB. Thanks to the discovery of HK199, HK201, HK225, HK253, and HK309, the number of TB cases known from the Sarmatian-period Carpathian Basin doubled, implying that the disease was likely more frequent in the Barbaricum than previously thought. Without the application of granular impressions, the diagnosis of TB could not have been established in these five cases. Thus, the identification of TB in these individuals highlights the importance of diagnostics development, especially the refinement of diagnostic criteria. Based on the above, the systematic macromorphological (re-)evaluation of osteoarchaeological series from the Sarmatian-period Carpathian Basin would be advantageous to provide a more accurate picture of how TB may have impacted the ancestral human communities of the Barbaricum.

Gender-specific differences in feasibility of pre-lacrimal window approach.

The feasibility and surgical effort of a pre-lacrimal window approach (PLWA) depends on the width of the bony window anterior to the nasolacrimal duct. This study aimed to investigate gender-specific differences in feasibility of PLWA. A consecutive series of paranasal computed tomography scans from 50 females (n = 100) and 50 males (n = 100) were retrospectively analyzed. The primary outcome measure was the antero-posterior length of the bony pre-lacrimal window (BPLWA). The secondary outcome measure was the distribution of Simmen's PLWA feasibility types (major, moderate and minor surgical effort). On average, males had a 1.5 mm (95% CI 0.8-2.2) significantly higher BPLW length in comparison to females [t(198) = 4.4, p < 0.0001]. The requirement of major surgical effort occurred 29% more frequently in females [χ2(1) = 17.7, p < 0.0001], whereas the necessity of moderate surgical effort was 21% more prevalent in males [χ2(1) = 8.8, p = 0.003]. The need of only minor surgical effort was twice as high in males compared to females [χ2(1) = 3, p = 0.081]. Our data indicates that females require more significant surgical effort during a PLWA to gain access to the maxillary sinus. These results are highly informative as a high amount of bone removal and nasolacrimal duct dislocation are associated with a higher likelihood of complications.

Alterations of pituitary adenylate cyclase-activating polypeptide-like immunoreactivity in the human plasma during pregnancy and after birth.

BACKGROUND: Since its discovery, several distinct effects of pituitary adenylate cyclase activating polypeptide (PACAP) have been established - predominantly in animal studies - in the nervous system, various peripheral organs as well as in the endocrine regulation. It is unknown whether PACAP has any effect on human pregnancy regarding either utero-maternal or perinatal aspects of the gestation. AIM: We investigated alterations of PACAP38-like immunoreactivity (PACAP38-LI) in the human plasma throughout normal pregnancy, during and after delivery, and its level in the umbilical vessels, as well as in the peripheral blood of term healthy newborns. MATERIALS AND METHODS: A 2 ml blood sample was used for each test, PACAP38-LI was determined by radioimmunoassay. RESULTS: In the 2nd and 3rd trimester significant elevation was observed in the PACAP38-LI compared to the earlier gestation and non-pregnant conditions. During delivery its level significantly decreased and returned to the original values 3 days after birth. In the neonates PACAP38-LI level of the peripheral blood was similar to that of healthy adults, but umbilical arteries and veins contained significantly lower concentrations of PACAP38-LI. Besides, the levels were lower in the umbilical vein compared to the artery. CONCLUSIONS: PACAP38-LI levels show sensitive change during normal pregnancy and delivery. Our findings suggest that the fetal organs actively synthesize PACAP. Further investigations are required to elucidate the physiological importance of the alterations observed.

Prenatal cigarette smoke exposure slightly alters neurobehavioral development in neonatal rats: Implications for developmental origins of health and disease (DoHAD).

Numerous studies indicate that smoking during pregnancy exerts harmful effects on fetal brain development. The aim of this study was to determine the influence of maternal smoking during pregnancy on the early physical and neurobehavioral development of newborn rats. Wistar rats were subjected to whole-body smoke exposure for 2 × 40 min daily from the day of mating until day of delivery. For this treatment, a manual closed-chamber smoking system and 4 research cigarettes per occasion were used. After delivery the offspring were tested daily for somatic growth, maturation of facial characteristics and neurobehavioral development until three weeks of age. Motor coordination tests were performed at 3 and 4 weeks of age. We found that prenatal cigarette smoke exposure did not alter weight gain or motor coordination. Critical physical reflexes indicative of neurobehavioral development (eyelid reflex, ear unfolding) appeared significantly later in pups prenatally exposed to smoke as compared to the control group. Prenatal smoke exposure also resulted in a delayed appearance of reflexes indicating neural maturity, including hind limb grasping and forelimb placing reflexes. In conclusion, clinically relevant prenatal exposure to cigarette smoke results in slightly altered neurobehavioral development in rat pups. These findings suggest that chronic exposure of pregnant mothers to cigarette smoke (including passive smoking) results in persisting alterations in the developing brain, which may have long-lasting consequences supporting the concept of developmental origins of health and disease (DoHAD).

The presence and distribution of pituitary adenylate cyclase activating polypeptide and its receptor in the snail Helix pomatia.

The aim of this study was to show the presence, distribution and function of the pituitary adenylate cyclase activating polypeptide (PACAP) and its receptors in the CNS and peripheral nervous system of the mollusk, Helix pomatia. PACAP-like and pituitary adenylate cyclase activating polypeptide receptor (PAC1-R)-like immunoreactivity was abundant both in the CNS and the peripheral nervous system of the snail. In addition several non-neuronal cells also revealed PACAP-like immunoreactivity. In inactive animals labeled cell bodies were mainly found and in the neuropile of active animals dense immunostained fiber system was additionally detected suggesting that expression of PACAP-like peptide was affected by the behavioral state of the animal. RIA measurements revealed the existence of both forms of PACAP in the CNS where the 27 amino acid form was found to be dominant. The concentration of PACAP27 was significantly higher in samples from active animals supporting the data obtained by immunohistochemistry. In Western blot experiments PACAP27 and PACAP38 antibodies specifically labeled protein band at 4.5 kDa both in rat and snail brain homogenates, and additionally an approximately 14 kDa band in snail. The 4.5 kDa protein corresponds to PACAP38 and the 14 kDa protein corresponds to the preproPACAP or to a PACAP-like peptide having larger molecular weight than mammalian PACAP38. In matrix-assisted laser desorption ionization time of flight (MALDI TOF) measurements fragments of PACAP38 were identified in brain samples suggesting the presence of a large molecular weight peptide in the snail. Applying antibodies developed against the PACAP receptor PAC1-R, immunopositive stained neurons and a dense network of fibers were identified in each of the ganglia. In electrophysiological experiments, extracellular application of PACAP27 and PACAP38 transiently depolarized or increased postsynaptic activity of neurons expressing PAC1-R. In several neurons PACAP elicited a long lasting hyperpolarization which was eliminated after 1.5 h continuous washing. Taken together, these results indicate that PACAP may have significant role in a wide range of basic physiological functions in snail.

Agonistic behavior of PACAP6-38 on sensory nerve terminals and cytotrophoblast cells.

The effects of pituitary adenylate cyclase activating polypeptide (PACAP) are mediated through G-protein-coupled receptors, the specific PAC1 receptor and VPAC1 and VPAC2 receptors which bind vasoactive intestinal peptide with similar affinity. Based on binding affinity studies, PACAP6-38 was discovered as a potent antagonist of PAC1 and it has been used by hundreds of studies as a PACAP antagonist. Recently, we have found that in certain cells/tissues, PACAP6-38 does not antagonize PACAP-induced effects, but surprisingly, it exerts similar actions to PACAP1-38, behaving as an agonist. In the present study, we report on the agonistic behavior of PACAP6-38 on neuropeptide release from sensory nerves of the isolated rat trachea and on the MAPK signaling pathways in cytotrophoblast cells. In isolated rat tracheae, PACAP6-38, similarly to PACAP1-38, induced significant inhibitory effects on the release of three simultaneously measured sensory neuropeptides, substance P, calcitonin gene-related peptide, and somatostatin evoked by both chemical excitation and electrical field stimulation of capsaicin-sensitive afferents. Effects of PACAP6-38 were the same as those of PACAP1-38 on MAPK signaling in human cytotrophoblast cells. Western blot analysis showed that both peptide forms stimulated ERK1/2 and JNK phosphorylation, while they both inhibited p38 MAPK phosphorylation. The most pronounced effects were observed when both peptides were present. In summary, our results show that PACAP6-38, which is a PACAP receptor antagonist in most cells/tissues, can behave as an agonist in other systems. The increasing interest in the effects of PACAP requires further studies on the pharmacological properties of the peptide and its analogues.

PKA-Bad-14-3-3 and Akt-Bad-14-3-3 signaling pathways are involved in the protective effects of PACAP against ischemia/reperfusion-induced cardiomyocyte apoptosis.

The neuropeptide PACAP (pituitary adenylate cyclase activating polypeptide) and its receptors are widely expressed in the nervous system and various other tissues. PACAP has well-known anti-apoptotic effects in neuronal cell lines. Recent data suggest that PACAP exerts anti-apoptotic effects also in non-neuronal cells. The peptide is present in the cardiovascular system, and has various distinct effects. The aim of the present study was to investigate whether PACAP is protective against in vitro ischemia/reperfusion-induced apoptosis in cardiomyocytes. Cultured cardiomyocytes were exposed to 60 min ischemia followed by 120 min reperfusion. The addition of PACAP1-38 significantly increased cell viability and decreased the ratio of apoptotic cells as measured by MTT test and flow cytometry. PACAP induced the phosphorylation of Akt and protein kinase A. In the present study we also examined the possible involvement of Akt- and protein kinase A-induced phosphorylation and thus inactivation of Bad, a pro-apoptotic member of the Bcl-2 family. It was found that ischemia significantly decreased the levels of phosphorylated Bad, which was counteracted by PACAP. Furthermore, PACAP increased the levels of Bcl-xL and 14-3-3 protein, both of which promote cell survival, and decreased the apoptosis executor caspase-3 cleavage. All effects of PACAP1-38 were inhibited by the PACAP antagonist PACAP6-38. In summary, our results show that PACAP has protective effects against ischemia/reperfusion-induced cardiomyocyte apoptosis and provides new insights into the signaling mechanisms involved in the PACAP-mediated anti-apoptotic effects.

Diazoxide is protective in the rat retina against ischemic injury induced by bilateral carotid occlusion and glutamate-induced degeneration.

Diazoxide (DIAZ) has been shown to be neuroprotective in animal models of different brain pathologies. However, the direct protective effect of DIAZ in different in vivo models of retinal degeneration has not yet been shown. Therefore, the aim of the present study was to investigate the neuroprotective role of this compound in two rodent model systems: monosodium-glutamate (MSG)- and chronic bilateral carotid artery occlusion (BCAO)-induced retinal degeneration. Rats were subjected either to s.c. MSG treatment on postnatal days 1, 5 and 9, or to BCAO at 2 months of age, followed by intravitreal DIAZ treatment. Histological examination was carried out 14 or 21 days after treatments, respectively. MSG treatment destroyed almost the entire inner retina, with the inner nuclear and ganglion cell layers being fused. DIAZ treatment significantly ameliorated the MSG-induced retinal degeneration. BCAO led to a severe degeneration of all retinal layers, and DIAZ proved to be protective also in this model. Our results may have clinical implications in reducing glutamate-induced excitotoxicity or ischemic retinal degeneration in ophthalmic diseases.

Changes in open-field activity and novelty-seeking behavior in periadolescent rats neonatally treated with monosodium glutamate.

Monosodium glutamate (MSG) treatment of neonatal rodents leads to degeneration of the neurons in the arcuate nucleus, inner retinal layers and various other brain areas. It also causes various changes in the motor activity, sensory performance and learning abilities. We have previously shown that MSG treatment delays the appearance of some reflexes during neurobehavioral development and leads to temporary changes in reflex performance and motor coordination. Investigation of novelty-seeking behavior is of growing importance for its relationship with sensitivity to psychomotor stimulants. Perinatal administration of numerous toxic agents has been shown to influence novelty-seeking behavior in rats, but little is known about the influence of neonatal MSG treatment on the novelty-seeking behavior. The aim of the present study was to compare changes in locomotor, spontaneous exploratory and novelty-seeking behavior in periadolescent rats neonatally treated with MSG. Newborn rats were treated with 4 mg/g MSG subcutaneously on postnatal days 1, 3, 5, 7 and 9. Open-field behavior was tested at 2, 3, 4, 6 and 8 weeks of age. We found that MSG administration led to only temporary increases in locomotor behavior, which was more pronounced during the first few postnatal weeks, followed by a subtle hypoactivity at 2 months of age. Novelty-seeking was tested in four 5-min trials at 3 weeks of age. Trial 1 was in an empty open-field, two identical objects were placed in the arena during trial 2 and 3, and one of them was replaced to a novel object during trial 4. We found that the behavioral pattern of MSG-treated rats was the opposite in all tested signs in the novelty exploration test compared to control pups. In summary, our present study shows that neonatal MSG treatment leads to early temporary changes in the locomotor activity followed by hypoactivity at 2 months of age. Furthermore, MSG-treated rats show a markedly disturbed novelty-seeking behavior represented by altered activity when subjected to a novel object.

Effects of systemic PACAP treatment in monosodium glutamate-induced behavioral changes and retinal degeneration.

The present article investigated effects of systemic pituitary adenylate cyclase-activating polypeptide (PACAP) treatment in monosodium glutamate (MSG)-induced retinal degeneration and neurobehavioral alterations in neonatal rats. It was found that the dose of PACAP that effectively enhances neurobehavioral development in normal rats was able to counteract the retarding effect of MSG on righting, forelimb placing, and grasp reflexes and caused a significant amelioration of the righting and gait reflex performance and motor coordination at 2 weeks of age. In the retina, significant amelioration of neuronal loss in the inner retinal layers was achieved, but it was much less than that observed by local administration.

Effect of PACAP in 6-OHDA-induced injury of the substantia nigra in intact young and ovariectomized female rats.

Pituitary adenylate cyclase activating polypeptide (PACAP) has neuroprotective effects in various neuronal cultures and in models of brain pathologies in vivo. Among others, it protects dopaminergic neurons in vitro, against 6-OHDA- and rotenone-induced injury. Recently, we have shown that PACAP reduces dopaminergic cell loss and ameliorates behavioral outcome following unilateral 6-OHDA-induced injury of the substantia nigra in male rats. However, after castration, PACAP led only to a slight amelioration of the behavioral symptoms. The aim of the present study was to investigate the degree of neuroprotection exerted by PACAP in female rats, using the same model. It was found that PACAP had no effect on the dopaminergic cell loss in intact female rats, only caused amelioration of certain acute behavioral signs. In contrast, PACAP effectively increased dopaminergic cell survival and decreased behavioral deficits in ovariectomized females. These results indicate that the neuroprotective effect of PACAP in a rat model of Parkinson's disease is gender-specific.

Nurses' health, age and the wish to leave the profession--findings from the European NEXT-Study.

BACKGROUND AND OBJECTIVES: In many industrialised countries the number of workers with low health is expected to increase in the nursing profession. This will have implications for occupational health work in health care. The European NEXT-Study (www. next-study. net, funded by EU) investigates working conditions of nurses in ten European countries and provides the opportunity to evaluate the role of health with respect to age and the consideration of leaving nursing. METHODS: 26,263 female registered nurses from Belgium, Germany, Finland, France, England, Italy, Netherlands, Poland and Slovakia were eligible for analysis. RESULTS: In most countries, older nurses considered leaving the profession more frequently than younger nurses. 'Health' was--next to 'professional opportunities' and 'work organisational factors'--strongly associated with the consideration of leaving nursing. However, more than half of all nurses with low health wanted to remain in the profession. This group reported rather positive psychosocial working conditions--but also the highest fear for unemployment. CONCLUSIONS: The findings indicate that 'the nurse with low health' is reality in many health care settings. Both positive supporting working conditions but also lack of occupational alternatives and fear of unemployment may contribute to this. Current economic, political and demographic trends implicate that the number of active nurses with low health will increase. Occupational health surveillance will be challenged by this. But NEXT findings implicate that prevention also will have to regard work organisational factors if the aim is to sustain nurses' health and to enable nurses to remain healthy in their profession until retirement age.

Pituitary Adenylate Cyclase Activating Polypeptide, A Potential Therapeutic Agent for Diabetic Retinopathy in Rats: Focus on the Vertical Information Processing Pathway.

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neurotrophic and neuroprotective peptide that has been shown to exert protective effects in different neuronal injuries, such as retinal degenerations. Diabetic retinopathy (DR), the most common complication of diabetes, affects the microvasculature and neuronal architecture of the retina. We have proven earlier that PACAP is also protective in a rat model of DR. In this study, streptozotocin-induced DR was treated with intravitreal PACAP administration in order to further analyze the synaptic structure and proteins of PACAP-treated diabetic retinas, primarily in the vertical information processing pathway. Streptozotocin-treated Wistar rats received intravitreal PACAP injection three times into the right eye 2 weeks after the induction of diabetes. Morphological and molecular biological (qRT-PCR; Western blot) methods were used to analyze retinal synapses (ribbons, conventional) and related structures. Electron microscopic analysis revealed that retinal pigment epithelium, the ribbon synapses and other synaptic profiles suffered alterations in diabetes. However, in PACAP-treated diabetic retinas more bipolar ribbon synapses were found intact in the inner plexiform layer than in DR animals. The ribbon synapse was marked with C-terminal binding protein 2/Bassoon and formed horseshoe-shape ribbons, which were more retained in PACAP-treated diabetic retinas than in DR rats. These results are supported by molecular biological data. The selective degeneration of related structures such as bipolar and ganglion cells could be ameliorated by PACAP treatment. In summary, intravitreal administration of PACAP may have therapeutic potential in streptozotocin-induced DR through maintaining synapse integrity in the vertical pathway.

Development of neurological reflexes and motor coordination in rats neonatally treated with monosodium glutamate.

Monosodium glutamate (MSG) treatment of neonatal rats causes neuronal degeneration in various brain areas and leads to several neurochemical, endocrinological and behavioral alterations. However, relatively little is known about the development of neurological reflexes and motor coordination of these animals. Therefore, the aim of the present study was to examine the neurobehavioral development of newborn rats treated with MSG. Rats received MSG at postnatal days 1, 3, 5, 7, and 9. Appearance of neural reflexes and reflex performance as well as motor coordination were examined for 5 weeks after birth. The efficacy of MSG treatment was confirmed by histological examination of the arcuate nucleus. We found that MSG treatment delayed the appearance of forelimb placing, forelimb grasp and righting reflexes, besides the retarded somatic development. The treated pups performed surface righting in significantly longer times. Also, worse performance was observed in the foot-fault and rota-rod tests. However, MSG-treated rats reached control levels by the end of the fifth postnatal week. These results show that MSG treatment does not cause permanent alterations in the neurobehavioral development, only delays the appearance of some reflexes and leads to temporary changes in reflex performance and motor coordination signs.

Intrapericardial infusion of endothelin-1 induces ventricular arrhythmias in dogs.

OBJECTIVES: Recently, extremely high levels of endothelin-1 (ET-1) were detected in the pericardial fluid of patients with heart disease; however, the pathophysiological importance of this finding is not known. The present study was designed to characterize ET-1 levels in canine pericardial fluid and to investigate the effects of local high concentrations of exogenous ET-1 in vivo. METHODS: In anesthetized, open-chest dogs ET-1 (Groups 1 and 2: 11 and 33 pmol.kg-1.min-1; n = 6 and 6, respectively) or physiological saline (Group 3, n = 5) were infused into the closed pericardial sac for 40 min. In serial pericardial fluid and aortic blood plasma samples, ET-1 levels were measured by radioimmunoassay, and analysed by high-performance liquid chromatography (HPLC). Systemic arterial blood pressure, heart rate, cardiac output (CO), standard ECG and right ventricular endocardial monophasic action potentials (MAPs) were recorded. RESULTS: Basal pericardial fluid ET-1 levels were significantly higher than respective plasma levels (342 +/- 210 vs. 8.0 +/- 5.2 pmol.l-1, n = 14, P < 0.001. In HPLC analysis pericardial fluid ET-1 was indistinguishable from ET-1(1-21). Infusion of exogenous ET-1 into the pericardial space induced ventricular arrhythmias in all instances, which were associated with 9.7-fold increase in pericardial fluid ET-1 levels. Ventricular tachycardias developed in 9 of 12 animals. The arrhythmogenic effect of ET-1 was more apparent in dogs with the larger dose. Before the onset of arrhythmias, intrapericardial infusion of ET-1 increased QT time (Group 1: 207 +/- 18 to 230 +/- 23 ms, P < 0.01; Group 2: 220 +/- 12 to 277 +/- 17 ms, P < 0.01) and MAP duration at 90% repolarization (at 300 ms cycle length) (Group 1: 192 +/- 9 to 216 +/- 9 ms, P < 0.01; Group 2: 205 +/- 9 to 255 +/- 9 ms, P < 0.001). Hemodynamic variables did not change significantly prior to the onset of ventricular tachyarrhythmias. In Group 3, arrhythmias were not observed and all electrophysiological and hemodynamic parameters remained unchanged. CONCLUSIONS: Administration of exogenous ET-1 into the pericardial space induces ventricular arrhythmias associated with prolongation of QT time and MAP duration. Whether pericardial fluid ET-1 under pathophysiological conditions can ever reach sufficiently high levels to induce ventricular arrhythmias remains to be elucidated.