Reproductive biology and nectar production of the Mexican endemic Psittacanthus auriculatus (Loranthaceae), a hummingbird-pollinated mistletoe.

Many mistletoe species produce 'bird'-pollinated flowers; however, the reproductive biology of the majority of these species has not been studied. Psittacanthus auriculatus is a Mexican endemic mistletoe, most common in open, dry mesquite grassland. Knowledge of the reproductive biology of P. auriculatus is essential for understanding species formation and diversification of Psittacanthus mistletoes, but it is currently poorly understood. Thus, we studied floral biology and phenology, nectar production and breeding system and pollination of this species. The hermaphroditic red-pink flowers open from the middle to the tip and petals are curly, but remain partially fused forming a floral tube of ca. 20-mm long. Flowers are partially protandrous, produce large amounts of nectar, last 2 days, and stigma receptivity is highest during the second day. We recorded hummingbirds (Cynanthus latirostris, Hylocharis leucotis, Amazilia beryllina, A. violiceps, Calothorax lucifer, Archilochus colubris) and less commonly butterflies (Agraulis vanillae, Anteos clorinde, Papilio multicaudatus, Phocides urania, Phoebis sennae) as floral visitors. P. auriculatus flowers are self-compatible. However, this mistletoe is an obligate animal-pollinated species, as the sensitive stigma avoids self-pollination. Under natural conditions, reproductive success was higher than in manually selfed or cross-pollinated flowers, likely due to the traplining foraging behaviour of hummingbirds. We suggest that the apparent efficient foraging behaviour of hummingbirds maintains gene flow among P. auriculatus, promoting outcrossing.

[Cilioretinal artery occlusion in hemochromatosis]. / Oclusión de arteria ciliorretiniana en la hemocromatosis.

CLINICAL CASE: We report a case of a 31 year-old woman with a sudden visual loss due to a cilioretinal artery occlusion. The physical examinination showed hepatomegaly. Serum iron and ferritin and transferrin saturation were unusually high. The doppler scan of carotid arteries showed no relevant signs of atheromatous disease. Dilated cardiomiopaty was revealed in the B-scan with subendocardial calcium deposits. Genetic tests were positive for hemochromatosis. DISCUSSION: Subendocardial calcification due to hemochromatosis could be the embolic source in our patient. This embolic ocular disease is the first presentation of hemochromatosis in this patient.

Two sampling time profiles for the abbreviated estimation of mycophenolic acid area under the curve in adult renal transplant recipients treated with mycophenolate mofetil and concomitant tacrolimus.

OBJECTIVE: Various studies have revealed that mycophenolic acid (MPA) area under the time concentration curve (AUC) may have clinical value in mycophenolate mofetil dose adjustment. As the full AUC measurement is impractical in clinical practice, several abbreviated AUC profiles using pre-dose, and two or three post-dose samples have been proposed; however, the possible use of lower sampling time profiles has an unquestionable practical interest, and the aim of our study was the evaluation of several two-points algorithms using only one post-dose sample. PATIENTS AND METHODS: In 60 MPA concentration-time profiles from 37 adult renal transplant patients treated with mycophenolate mofetil and concomitant tacrolimus, the MPA AUC values were estimated using the three sampling time algorithm (pre-dose, one-half and 2 h post-dose)of Pawinski et al. (Clinical Chemistry 48, 2002, 1497), trapezoidal extrapolated procedure according to Hale et al. (Clinical Pharmacology Therapeutics 64, 1998, 672), and two-points algorithm (pre-dose and 2 h post-dose) proposed by David-Neto et al. (Clinical Transplantation 19, 2005, 19). RESULTS: The AUC values estimated using the algorithm of Pawinski et al. had a very high correlation(r = 0.997, P < 0.001) with the trapezoidal extrapolated AUC results. The estimated AUC values obtained using the two-points algorithm of David-Neto et al. present a high correlation (r = 0.930, P < 0.001), acceptable mean prediction error (+3.3 +/- 1.8%), and a diagnostic efficiency of 94% in the classification of subtherapeutic, therapeutic, and supratherapeutic values, with respect to the three-points algorithm of Pawinskiet al. CONCLUSION: The two sampling time algorithm of David-Neto gave similar results to those of the three-sampling time algorithm of Pawinski, and both, with sampling over 2 h, may be useful for routine MPA AUC estimation in renal transplant recipients with concomitant tacrolimus. Both are unsuitable when unusually unpredictable pharmacokinetics are expected such as with entericcoated formulations.

[Congenital disorder of glycosylation type 1b. Experience with mannose treatment]. / Defecto congénito de glucosilación tipo Ib. Experiencia en el tratamiento con manosa.

Congenital disorders of glycosylation (CDG) are recessively inherited multisystemic disorders resulting from several genetic defects affecting the assembly, transfer or processing of oligosaccharides onto proteins and other glycoconjugates. CDG type Ib is due to a deficiency of phosphomannose isomerase (PMI) encoded by the MPI gene. PMI catalyzes the interconversion of fructose-6-P and mannose-6-P. The clinical phenotype is characterized by gastro-intestinal and hepatic symptoms. In contrast to most CDG patients, there is no neurological affectation. It's a mannose treatable disorder. We report the first recognised case of CDG Ib in Spain. He presented at 6 months with hypoglycaemia, failure to thrive and hypertransaminasaemia. He subsequently developed an enteropathy with subtotal villous atrophy on biopsy. The %CDT was very high and he presented with a type 1 pattern in transferrin isoelectric focusing. PMI activity in fibroblasts was very deficient. Mutations in MPI gene at R219Q and R56fs were found. Clinical and biochemical parameters normalised after treatment with mannose 1 g/kg/day in 5 doses. CDG Ib should be considered in patients with hypoglycaemia, liver disease, enteropathy and hypercoagulability, in the absence of other common causes, and particularly if some of them are combined.

The atherosclerotic plaque.

Atherosclerosis is the most frequent cause of ischemic heart disease and cerebrovascular disorders. The condition is the leading cause of death in Western societies. At the core of this condition is the atherosclerotic plaque. It is within the structure of this lesion that multiple biochemical and cellular processes interact influencing its vulnerability to rupture and as a result acute ischemic events. This article will discuss the pathophysiology behind the atherosclerotic plaque, particularly those elements that lead to its instability and the medical tools currently available to counteract it.

[Lipase and total amylase and its isoenzymes as markers of pancreatic injury in patients treated with antiepileptic drugs]. / Lipasa y amilasa total y sus isoenzimas como marcadores de daño pancreático en pacientes tratados con fármacos antiepilépticos.

OBJECTIVE: The study of the serum lipase and total amylase and its isoenzymes as biochemical markers of pancreatic injury in patients treated with valproic acid and other enzyme-inducing antiepileptic drugs. METHOD: The serum activities of lipase and total amylase and its isoenzymes were determined in 41 patients treated in monotherapy with valproic acid, 50 patients in mono/polytherapy with phenytoin, phenobarbital and carbamazepine, and 30 healthy controls. RESULTS: In the first group of patients a clinically significant difference in relation to the control group was not obtained for any of the enzyme activities studied; however, in the group of patients treated with enzyme-inducing antiepileptic drugs clinically significant differences were obtained for lipase and pancreatic amylase. In this group of patients, the activity of pancreatic amylase was clearly increased in two cases (4%), suggesting the existence of a pancreatic damage. In the patients studied, the total amylase showed a poor specificity as a biochemical marker for pancreatic injury, and the greater serum activity observed in one case corresponds to an increase of the salivar isoenzyme. The sensitivity of the lipase is smaller than amylase pancreatic isoenzyme. CONCLUSIONS: In patients treated with antiepileptic drugs, the determination of the pancreatic isoenzyme of amylase would be of interest even in absence of clinical signs for acute pancreatitis.

Lipasa y amilasa total y sus isoenzimas como marcadores de daño pancreático en pacientes tratados con fármacos antiepilépticos / No disponible

Objetivo: El estudio de la lipasa y amilasa total y sus isoenzimasen suero como indicadores bioquímicos de daño pancreáticoen pacientes tratados con ácido valproico y con otros fármacosantiepilépticos inductores enzimáticos.Método: Se determinaron las actividades séricas de lipasa yamilasa total y sus isoenzimas en 41 pacientes tratados con ácidovalproico en monoterapia, 50 pacientes tratados en mono/politerapiacon fenitoína, fenobarbital y carbamazepina y 30 controlesclínicamente sanos.Resultados: En el primer grupo de pacientes no se encontróuna diferencia clínicamente significativa en relación al grupo controlpara ninguna de las actividades enzimáticas; sin embargo, enel grupo tratado con fármacos antiepilépticos inductores seencontró una diferencia clínicamente significativa para la lipasa yamilasa de tipo pancreático. En este grupo de pacientes, en2 casos (4%) la actividad de amilasa pancreática estaba claramenteaumentada con niveles que sugerían la existencia de un dañopancreático. La amilasa total presentó una deficiente especificidadcomo marcador bioquímico de daño pancreático en los pacientesestudiados, correspondiendo la mayor actividad encontrada a uncaso con aumento de la isoenzima de tipo salivar. Por su parte lalipasa parece presentar una menor sensibilidad.Conclusiones: En pacientes tratados con fármacos antiepilépticosla determinación de la isoenzima de tipo pancreático de laamilasa podría ser de interés aun en ausencia de signos clínicos depancreatitis aguda

Objective: The study of the serum lipase and total amylaseand its isoenzymes as biochemical markers of pancreatic injury inpatients treated with valproic acid and other enzyme-inducingantiepileptic drugs.Method: The serum activities of lipase and total amylase andits isoenzymes were determined in 41 patients treated inmonotherapy with valproic acid, 50 patients in mono/polytherapywith phenytoin, phenobarbital and carbamazepine, and 30healthy controls.Results: In the first group of patients a clinically significantdifference in relation to the control group was not obtained forany of the enzyme activities studied; however, in the group ofpatients treated with enzyme-inducing antiepileptic drugs clinicallysignificant differences were obtained for lipase and pancreaticamylase. In this group of patients, the activity of pancreaticamylase was clearly increased in two cases (4%), suggestingthe existence of a pancreatic damage. In the patients studied,the total amylase showed a poor specificity as a biochemicalmarker for pancreatic injury, and the greater serum activityobserved in one case corresponds to an increase of the salivarisoenzyme. The sensitivity of the lipase is smaller than amylasepancreatic isoenzyme.Conclusions: In patients treated with antiepileptic drugs, thedetermination of the pancreatic isoenzyme of amylase would be ofinterest even in absence of clinical signs for acute pancreatitis

Neumonía lipoidea endógena asociada a enfisema / No disponible

No disponible

Angiotensin II-dependent vascular alterations in young cardiomyopathic hamsters: role for oxidative stress.

Recent studies indicate the presence of vascular alterations in 2-month-old Syrian cardiomyopathic hamsters (SCH). These alterations include enhanced angiotensin-converting enzyme (ACE) activity in the aorta, increased contractile response to angiotensin II and impaired vasorelaxation to acetylcholine in norepinephrine-precontracted aortic rings. The mechanisms leading to these vascular alterations are not known nor has their relationship to the cardiac abnormalities been established. We assessed the status of the cardiovascular system of 2-month-old hamsters first to establish if the observed vascular alterations are secondary to cardiac dysfunction, and second to examine the role of oxidative stress in the etiology of vascular dysfunction. Cardiac function parameters evaluated by echocardiography included stroke volume (SV), left ventricular end-diastolic volume (LVEDV), left ventricular fractional shortening (LVFS), ejection fraction (EF), cardiac output index (COI), heart rate (HR) and left ventricular posterior wall thickness (LVPWT). In addition, heart/body weight (heart/BW) ratios and systolic blood pressure were determined in normal hamsters and SCH. Our results indicated that systolic blood pressure increased 56% in SCH when compared to control animals (P<0.05). The increased blood pressure coexisted with normal COI, SV, LVEDV, LVPWT, LVFS, EF, HR and heart/BW ratios. NAD(P)H oxidase activity increased 77% in SCH compared to control animals (P<0.02). The increased oxidase activity was abolished by pre-treatment of animals with the angiotensin II type 1 receptor blocker losartan (25 mg/kg BW/day) for 10 days. Losartan also abolished the increased blood pressure observed at 2 months of age. The antioxidant N-acetylcysteine (NAC) abrogated the increased blood pressure when administered for 30 days to 1-month-old animals. Altogether, these findings suggest that the angiotensin II-dependent vascular abnormalities present in young cardiomyopathic hamsters are associated with oxidative stress and precede the echocardiographic abnormalities characteristic of heart failure.

[Orbital involvement as the first manifestation of Hand-Schuller-Christian disease. A case report]. / AFectación orbitaria como primera manifestación de la enfermedad de Hand-Schuller-Christian. Caso clínico.

UNLABELLED: PURPOSE/MATERIAL AND METHOD: To describe the clinical case of a 20-month-old boy with Hand-Schuller-Christian disease. Exophthalmos was the only systemic manifestation evident over a period of at least 6 weeks, but later the triad of exophthalmos with multiple lytic lesions of the skull and diabetes insipidus were present. RESULTS/CONCLUSION: Histiocytosis X should be considered in the differential diagnosis of orbital tumors in children.

Afectación orbitaria como primera manifestación de la enfermedad de Hand-Schuller-Christian. Caso clínico / Orbital involvement as the first manifestation of Hand-Schuller-Christian disease. A case report

Objetivo/Método: Describir el caso clínico de un niño de 20 meses con enfermedad de Hand-Schuller-Christian. Un exoftalmos fue la única clínica del proceso, al menos durante 6 semanas, después apareció la tríada característica de exoftalmos con múltiples lesiones líticas en el cráneo y diabetes insípida.Resultados/Conclusión: La histiocitosis X se debe incluir en el diagnóstico diferencial de tumores orbitarios en el niño

Purpose/Material and Method: To describe the clinical case of a 20-month-old boy with Hand-Schuller-Christian disease. Exophthalmos was the only systemic manifestation evident over a period of at least 6 weeks, but later the triad of exophthalmos with multiple lytic lesions of the skull and diabetes insipidus were present. Results/Conclusion: Histiocytosis X should be considered in the differential diagnosis of orbital tumors in children

Enalapril improves vascular and cardiac function in streptozotocin-diabetic rats.

Recent evidence points to the renin-angiotensin system (RAS) as one of the systems involved in the etiology of micro- and macrovascular disease in diabetic patients. To help elucidate this possibility, the effect of daily treatment with enalapril (25 mg/kg/d) was evaluated in streptozotocin (STZ)-diabetic rats at 2 weeks following the induction of diabetes. Untreated diabetic rats and non-diabetic rats that were age-matched were used for comparison. Vascular studies included the determination of aortic ring responses to norepinephrine (NE), angiotensin II (Ang II) and acetylcholine (Ach). Systolic blood pressure (SBP), cardiac output (CO) indices, plasmatic and vascular angiotensin-converting enzyme (ACE) activity and thickness of the aortic wall were also assessed. Enalapril improved Ach-induced relaxation by increasing the maximal relaxation from 54.3 +/- 4.3% in untreated diabetic rats to 89.8 +/- 6.2% (n=9, p<0.05) and by decreasing the EC50 value from 32.6 +/- 9.9 nmol/l in untreated diabetic animals to 17.9 +/- 5.1 nmol/l (n=8, p<0.05). In addition, enalapril normalized the high responses to NE found in diabetic rats without inducing changes in the EC50 value. A significant reduction in SBP (from 158 +/- 4 mm Hg to 123 +/- 1 mm Hg, p<0.05), combined with an improved CO index (from 40 +/- 2 ml/min x 100 g BW to 50 +/- 1 ml/min x 100 g BW), was observed in the enalapril-treated diabetic group. A significant regression of the media thickness was also observed in the aorta of diabetic rats after treatment. ACE activity in the aorta of diabetic rats, that was doubled compared to controls (p<0.05), decreased after enalapril treatment. These results point to the vascular RAS as one of the key systems in the etiology of vascular alterations at early stages of diabetes. Therefore, ACE inhibitors, as well as other pharmacological approaches targeting the vascular RAS, should be considered in the treatment of diabetic patients from the very early stages of the condition.

[A study of some indirect biochemical markers in the evaluation of enzymatic induction caused by antiepileptic drugs]. / Estudio de algunos marcadores bioquímicos indirectos en la evaluación de la inducción enzimática por fármacos antiepilépticos.

A comparative study was carried out to examine urinary excretion of D glucaric acid (DGA), g glutamyltransferase (GGT) activity and the concentration of serum bilirubin as enzymatic induction markers in 89 adult patients (56 men and 33 women) who were receiving chronic treatment with phenobarbital, phenytoin, carbamazepine and valproate. As in most cases, these drugs were administered as a polytherapy; drugs doses were expressed in units/day, in accordance with a previously described system of scoring, which would reflect the induction capacity of the combination of drugs administered. We found a high prevalence of results that were above the upper reference limit for urinary DGA (93.2%) and serum GGT (80.6%). Bilirubin and its conjugate and non conjugate fractions were found to offer values that to a large extent matched those of the control group. The levels of the different biochemical variables presented significant correlations with the daily doses of the drugs administered, above all in the case of DGA (r= 0.773, p< 0.001). When we split the data according to sex, the correlations improved in men but were significantly worse in women. This fact could be due to a greater inter individual variability in the response to inducers of the phenobarbital type in female patients. Urinary DGA seems to be a better enzymatic induction marker than GGT and bilirubin and its serum fractions, the value of which appeared to be very limited in these cases. Separating GGT into its isoforms provided no further information of practical interest as regards the enzymatic activity as a whole.

Estudio de algunos marcadores bioquímicos indirectos en laevaluación de la inducción enzimática por fármacos antiepilépticos / A study of some indirect biochemical markers in the evaluation of enzymatic induction caused by antiepileptic drugs

Pacientes y métodos. Se hizo un estudio comparativo de la excreción urinaria de ácido D-glucárico (ADG) y actividad de gamma -glutamiltransferasa (GGT) y concentración de bilirrubina séricas como marcadores de inducción enzimática en 89 pacientes adultos -56 hombres y 33 mujeres- que recibían un tratamiento crónico con fenobarbital, fenitoína, carbamacepina y valproato. Como en la mayoría de los casos, estos fármacos se administraban en politerapia; la dosificación se expresó en unidades/día, de acuerdo con un sistema de puntuación previamente descrito, que reflejaría la capacidad inductora de la combinación de fármacos administrados. Resultados. Se encontró una elevada prevalencia de resultados mayores que el límite superior de referencia para el ADG urinario (93,2 por ciento) y GGT sérica (80,6 por ciento). Con respecto a la bilirrubina y sus fracciones conjugada y no conjugada se encontró un gran solapamiento de los valores con relación al grupo control. Los niveles de las distintas variables bioquímicas presentaron correlaciones significativas con la dosificación diaria de los fármacos administrados, sobre todo en el caso del ADG (r= 0,773, p< 0,001). Al hacer una dicotomía en función del sexo, mejoraron las correlaciones en los hombres y empeoraron de forma significativa en las mujeres. Este hecho podría deberse a una mayor variabilidad interindividual de respuesta a los inductores tipo fenobarbital en los pacientes de sexo femenino. Conclusiones. El ADG urinario parece un mejor marcador de inducción enzimática que la GGT y la bilirrubina y sus fracciones séricas, cuya utilidad parece muy limitada en estos casos. La separación de las isoformas de la GGT no proporcionó ninguna información adicional de interés práctico con respecto a la actividad enzimática total (AU)

Occurrence of Malassezia spp. in the external ear canals of dogs and cats with and without otitis externa.

We studied the lipophilic microbiota of the external ear canals of 332 animals (264 dogs and 68 cats), with and without otitis externa, over an 11-year period from 1988 to 1999. Malassezia pachydermatis was isolated from 62.2% and 50% of dogs with and without otitis externa, respectively, and from 41.2% and 17.6% of cats with and without otitis externa, respectively. In the group of animals studied for lipid-dependent species, these yeasts were isolated from 4.5% of dogs with otitis externa and from 23.1% and 8.9% of cats with and without otitis externa, respectively. M. sympodialis and M. furfur were isolated from cats and M. furfur and M. obtusa from dogs. Our findings show that lipid-dependent Malassezia species may contribute to the etiology of otitis externa in dogs and cats.

Occurrence of Malassezia spp. in horses and domestic ruminants.

During a study on the occurrence of Malassezia spp. in 112 animals (50 horses, 25 goats, 25 sheep and 12 cows), Malassezia spp. were isolated from 60% of horses, 28% of sheep, 44% of goats and 58% of cows. In these animals, the occurrence of lipid-dependent species (42%) was much greater than the occurrence observed for M. pachydermatis (3%). Among the results obtained, we point out the first isolation of M. sympodialis, M. globosa and M. restricta from sheep, M. pachydermatis, M. furfur, M. sympodialis, M. obtusa, M. globosa and M. restricta from goats and M. furfur, M. slooffiae, M. obtusa, M. globosa and M. restricta from horses. To the authors' knowledge, this survey also states the first description of the presence of M. restricta in animals.

Chronic administration of losartan plus hydrochlorothiazide improves vascular status in young cardiomyopathic hamsters.

The combination of an angiotensin II receptor antagonist and a thiazide has been used extensively in the treatment of patients with overt heart failure. The effect of this combination on the vascular wall early in the disease, however, has not been investigated. To evaluate this effect, the vascular status of 3-month-old cardiomyopathic hamsters was assessed after daily administration of a combination of losartan (25 mg/kg, p.o.) and hydrochlorothiazide (6.5 mg/kg, p.o.) over an 8-week period. Age-matched golden hamsters were used as healthy controls. The contractile response of aortic rings to endothelin-1 was significantly higher in cardiomyopathic hamsters than in control animals. Concentration-response curves for the endothelin-1-induced contraction were displaced to the right after hydrochlorothiazide+losartan treatment (toward the curves for healthy controls); however, E(max) from treated hamsters was significantly reduced when compared to E(max) from untreated cardiomyopathic animals (1.016+/-0.073 vs. 1.346+/-0.153 g, P<0.05, n=6). No significant differences in the EC50 values from these curves were observed between hydrochlorothiazide+losartan treated and untreated cardiomyopathic animals (2.90+/-0.95 vs. 1.10+/-0.85 nM, P>0.05). The acetylcholine-induced relaxation observed in cardiomyopathic animals was not improved after treatment with hydrochlorothiazide+losartan or hydrochlorothiazide alone, but the combination of these drugs increased significantly the basal production of nitric oxide (NO). Angiotensin-converting enzyme activity increased in plasma (from 29.9+/-1.23 to 41.16+/-1.82 nmol x mg(-1) x min(-1), n=8, P<0.05) but decreased in the aorta (from 0.33+/-0.02 to 0.25+/-0.017 nmol x mg(-1) x min(-1), n=6, P<0.05) after treatment with hydrochlorothiazide+losartan. In addition, the combination of these drugs reduced the heart-to-body mass ratio (3.96+/-0.07 for treated vs. 5.01+/-0.20 mg/g for untreated animals, n=7, P<0.05), and the thickness of the aortic media (0.076+/-0.003 for treated vs. 0.149+/-0.009 mm for untreated animals, n=8, P<0.05). Although hydrochlorothiazide alone lowered systolic blood pressure to the same level achieved with both drugs in combination (from 166+/-10 for untreated cardiomyopathic animals to 84+/-1 mm Hg for hydrochlorothiazide+losartan, and 80+/-5 mm Hg for hydrochlorothiazide alone, P<0.05), no significant reduction in heart-to-body mass ratio was observed in animals treated with the diuretic alone (P>0.05). In conclusion, in this model of heart failure, chronic hydrochlorothiazide+losartan administration normalizes the vascular responses to endothelin-1, improves basal vascular tone, and prevents the development of cardiac and vascular hypertrophy.

Evaluation of different preservation and storage methods for Malassezia spp.

Freezing at -80 degrees C, lyophilization, preservation in distilled water, and storage in different culture media were performed in order to find a suitable method that allowed a prolonged storage of Malassezia spp. Freezing at -80 degrees C was the only method successful at maintaining all species.

Interaction between AT1 and alpha1-adrenergic receptors in cardiomyopathic hamsters.

BACKGROUND: Cross talk between angiotensin AT1 and alpha1-adrenergic receptors has been reported previously and points to the existence of physiologic regulation between the renin-angiotensin system and the sympathetic nervous system at the receptor level. This regulation may play an important role in the control of blood pressure and may be modified in different cardiovascular pathologies. Nevertheless, neither the physiologic actions nor the clinical relevance of the interaction between these 2 receptors has yet been established. To reveal these aspects in relation to heart failure, the interaction between vascular AT1 and alpha1-adrenergic receptors was evaluated in the Syrian cardiomyopathic hamster model. METHODS AND RESULTS: The vascular response of each individual receptor to vasoactive agonist was assessed in the presence and absence of antagonists of the other receptor using aortic rings from 11-month-old Syrian cardiomyopathic hamsters. Age-matched golden hamsters were used as controls. In control hamsters, concentration-response curves for the norepinephrine (NE)-induced contraction were significantly displaced to the left after 100 mmol/L losartan incubation. The maximal tension achieved (Emax) values increased by 26+/-4.3% after incubation (P < .05). Similar results were obtained when 20 micromol/L enalapril was used to block angiotensin II (Ang II) synthesis. NE concentration-response curves were also displaced to the left and Emax increased by 27%+/-8.0% (P < .05). The concentrations that induce 50% of the maximal contraction (EC50) were 22.2+/-0.2 nmol/L for untreated and 27.1+/-2.0 nmol/L for losartan-treated aortic rings (n = 8, P > .05). However, EC50 values were significantly reduced in aortic rings treated with enalapril (7.51+/-0.16 nmol/L, n = 8, P < .05). Blockade of alpha1 receptor with 10 micromol/L prazosin increased the response to Ang II by 32% (n = 6, P < .05). In contrast, when these experiments were repeated in aortic rings from cardiomyopathic animals, no interaction between the 2 receptors was observed. NE concentration-response curves, Emax (9.6%+/-2.8% increase after enalapril. and 5.8%+/-6.5% increase after losartan, P > .05) and EC50 values (14.7+/-0.7 nmol/L without treatment, 17.5+/-1.5 nmol/L with enalapril and 11.1+/-0.8 with losartan, n = 8, P > .05) were similar. Furthermore, in cardiomyopathic animals, prazosin did not modify the vascular response to Ang II. CONCLUSIONS: An interaction exists between vascular AT1 and alpha1-adrenergic receptors in control hamsters but not in cardiomyopathic animals. This interaction seems to be bidirectional and counterregulatory. The lack of this regulation may promote a state of enhanced vascular wall activity, which could contribute to the increased vasoconstriction and total peripheral resistance characteristic of heart failure.