New insights on the association of weight loss with the reduction in carotid intima-media thickness among patients with obesity: an updated systematic review and meta-analysis

OBJECTIVES

Carotid intima-media thickness (CIMT) is a noninvasive marker of atherosclerosis, a typical pathologic process underlying cardiovascular diseases (CVDs). It is essential to explore the relationships between weight loss and the reduction of CIMT.

STUDY DESIGN

This was an updated systematic review and meta-analysis.

METHODS

A systematic literature search was conducted to collect relevant clinical trials. The pooled results of meta-analyses were assessed by weighted mean difference (WMD) and the corresponding 95 % confidence interval (95% CI).

RESULTS

Thirty-three articles involving 2273 participants were collected in this meta-analysis. Among all participants with obesity, the pooled mean of weight loss was -23.26 kg (95% CI: -27.71 to -18.81), and the pooled mean change of CIMT was -0.06 mm (95% CI: -0.08 to -0.04). Compared with Non-surgical interventions, Surgical ones could lead to much higher weight loss (Pbetween groups < 0.001). A more significant CIMT reduction was identified among Surgical intervention patients than among Non-surgical intervention participants (Pbetween groups < 0.001).

CONCLUSIONS

Effective interventions, especially Surgical interventions, could reduce the weight of patients with obesity, followed by the decline of CIMT, which might further disturb atherosclerosis progression and lower CVD risk.

[Efficacy and safety of bendamustine-rituximab combination therapy for newly diagnosed indolent B-cell non-Hodgkin's lymphoma and elderly mantle cell lymphoma: a multi-center prospective phase II clinical trial in China]

Objectives: This study aimed to assess the efficacy and safety of bendamustine in combination with rituximab (BR regimen) for the treatment of newly diagnosed indolent B-cell non-Hodgkin's lymphoma (B-iNHL) and elderly mantle cell lymphoma (eMCL) . Methods: From December 1, 2020 to September 10, 2022, a multi-center prospective study was conducted across ten Grade A tertiary hospitals in Shandong Province, China. The BR regimen was administered to evaluate its efficacy and safety in newly diagnosed B-iNHL and eMCL patients, and all completed at least four cycles of induction therapy. Results: The 72 enrolled patients with B-iNHL or MCL were aged 24-74 years, with a median age of 55 years. Eastern Cooperative Oncology Group (ECOG) performance status scores of 0-1 were observed in 76.4% of patients, while 23.6% had scores of 2. Disease distribution included follicular lymphoma (FL) (51.4% ), marginal zone lymphoma (MZL) (33.3% ), eMCL (11.1% ), and the unknown subtype (4.2% ). According to the Ann Arbor staging system, 16.7% and 65.3% of patients were diagnosed with stage Ⅲ and stage Ⅳ lymphomas, respectively. Following four cycles of BR induction therapy, the overall response rate was 98.6%, with a complete response (CR) rate of 83.3% and a partial response (PR) rate of 15.3%. Only one eMCL patient experienced disease progression during treatment, and only one FL patient experienced a relapse. Even when evaluated using CT alone, the CR rate was 63.9%, considering the differences between PET/CT and CT assessments. The median follow-up duration was 11 months (range: 4-22), with a PFS rate of 96.8% and an OS rate of 100.0%. The main hematologic adverse reactions included grade 3-4 leukopenia (27.8%, with febrile neutropenia observed in 8.3% of patients), grade 3-4 lymphopenia (23.6% ), grade 3-4 anemia (5.6% ), and grade 3-4 thrombocytopenia (4.2% ). The main non-hematologic adverse reactions such as fatigue, nausea/vomiting, rash, and infections occurred in less than 20.0% of patients. Conclusion: Within the scope of this clinical trial conducted in China, the BR regimen demonstrated efficacy and safety in treating newly diagnosed B-iNHL and eMCL patients.

[Preliminary exploration of the metabolic profile and metabolic pathways in newly diagnosed multiple myeloma]

Objective: To explore the metabolite profile and metabolic pathways of newly diagnosed multiple myeloma (MM). Methods: Gas chromatography-mass spectrometry (GC-MS) was employed for the high-throughput detection and identification of serum samples from 55 patients with MM and 37 healthy controls matched for age and sex from 2016 to 2017 collected at the First Affiliated Hospital of Soochow University. The relative standard deviation (RSD) of quality control (QC) samples was employed to validate the reproducibility of GC-MS approach. The differential metabolites between patients with MM and healthy controls were detected by partial least squares discrimination analysis (PLS-DA), and t-test with false discovery rate (FDR) correction. Metabolomics pathway analysis (MetPA) was employed to construct metabolic pathways. Results: There were 55 MM patients, including 34 males and 21 females. The median age was 60 years old (42-73 years old). There were 30 cases of IgG type, 9 cases of IgA type, 1 case of IgM type, 2 cases of non-secreted type, 1 case of double clone type and 12 cases of light chain type, including 3 cases of kappa light chain type and 9 cases of lambda light chain type. The result of QC sample test showed that the proportion of compounds with the RSD of the relative content of metabolites < 15% was 70.21% obtained by the reproducibility of GC-MS experimental data, which implied that the experimental data were reliable. A total of 17 metabolites were screened differently with the healthy control group, including myristic acid, hydroxyproline, cysteine, palmitic acid, L-leucine, stearic acid, methionine, phenylalanine, glycerin, serine, isoleucine, tyrosine, valine, citric acid, inositol, threonine, and oxalic acid (VIP>1, P<0.05). Metabolic pathway analysis suggested that metabolic disorders in MM patients comprised mainly phenylalanine metabolism, glyoxylic acid and dicarboxylic acid metabolism, phosphoinositide metabolism, cysteine and methionine metabolism, glycerolipid metabolism, glycine, serine, and threonine metabolism. Conclusion: Compared with normal people, patients with newly diagnosed MM have obvious differences in metabolic profiles and metabolic pathways.

Lamin B1 deficiency promotes malignancy and predicts poor prognosis in gastric cancer

Gastric cancer (GC) is a kind of global malignancy. However, the expression pattern and clinical relevance of lamin B1 in GC remain to be elucidated. We endeavored to investigate how GC is influenced by lamin B1 and the related mechanisms. The lamin B1 expression in GC tissues from 71 patients was assessed by using immunohistochemistry (IHC). The expression of lamin B1 was connected with the clinical stage, depth of invasion, and poorer overall survival. Colony formation assays and methyl thiazolyl tetrazolium (MTT) were used to assess cell viability. The migration ability of GC cells was determined by cell scratch assay and Transwell invasion assay. Moreover, we used two cell lines of GC to explore the underlying mechanism of lamin B1 in boosting the GC cells proliferation and invasion in vitro by assessing the effects on related signal transduction pathways. Our data demonstrated that the expression level of lamin B1 was downregulated in GC tissues, and low expression level of lamin B1 was significantly correlated with higher clinical stage, depth of invasion, nodal stage, and poor prognosis. Moreover, in vitro experiments demonstrated that lamin B1 knockdown promoted, whereas lamin B1 overexpression inhibited, gastric cancer cell proliferation and migration. We also observed that lamin B1 knockdown could promote the activity of the PI3K/PTEN/Akt and MAPK/ERK pathway with a decrease in the p53/p21WAF1/CIP1 expression, whereas lamin B1 overexpression contributed to the opposite results. In conclusion, our studies indicate that lamin B1 deficiency is crucial in GC progression. Furthermore, the results elucidating the biological mechanisms of lamin B1 may potentially contribute to current GC treatment modalities.

[Discussion on the indications of internal mammary sentinel lymph node biopsy in breast cancer in the era of precision medicine]

Objective: To determine the clinical benefits of internal mammary sentinel lymph node biopsy (IM-SLNB) acquired by breast cancer patients with clinically positive axillary lymph node (ALN), and further optimize the IM-SLNB indications. Methods: All primary breast cancer patients with clinically positive ALN from February 2014 to September 2017 were prospectively recruited in this study. IM-SLNB was performed under the guidance of the modified injection technique. The success rate and visualization rate of IM-SLNB, metastatic rate of internal mammary sentinel lymph node (IMSLN) and its related factors were analyzed, and the clinical benefits were accessed according to the current guidelines. Results: Among 126 patients, all of 94 patients (74.6%) who showed internal mammary drainage successfully underwent IM-SLNB. The incidence of internal mammary artery bleeding and pleural lesion were 4.3%(4/94) and 9.6%(9/94), respectively. The metastatic rate of IMSLN was 38.3% (36/94), which was significantly associated with the number of positive ALN (P<0.001) and tumor size (P=0.024). The lymph node staging of 94 patients who underwent IM-SLNB was more accurate. Among them, 36 cases with positive IMSLN underwent internal mammary radiotherapy (IMRT), while the other 58 cases with negative IMSLN avoided radiotherapy. Conclusions: IM-SLNB should be routinely performed in patients with positive ALN. IM-SLNB can provide more accurate staging and guide tailored IMRT to benefit more breast cancer patients.

Continuously wavelength-tunable blueshifting soliton generated in gas-filled photonic crystal fibers

We experimentally report the generation of wavelength-tunable blueshifting soliton in the visible spectral region through a gas-filled single-ring photonic crystal fiber (SR-PCF). In particular, in a He-filled SR-PCF, we observed a sharp narrow-band spectral peak at the first resonant spectral region of the SR-PCF, which results from phase-matched nonlinear processes. To the best of our knowledge, this is the first time investigating the influence of the core-cladding resonance on the blueshifting soliton. In addition, when Ar gas was filled into the SR-PCF, some interference fringes on the blueshifting soliton were observed at high pulse-energy levels due to plasma-induced pulse fission. These two experimental observations are confirmed by numerical simulations. Furthermore, through properly adjusting input pulse energy, we found that the blueshifting soliton can obtain a high conversion efficiency (∼84%) and its wavelength can be tuned over hundreds of nanometers (∼240  nm).

[Effects of prenatal maternal seizure on hippocampal damage and cognitive deficits in offspring rats]

Objective: To observe hippocampal damage and cognitive impairment of offspring exposed to prenatal maternal seizure induced by amygdala kindling, and to explore the underlying mechanism by the detection of pathological changes of placenta. Method: Adult female SD rats were randomly divided into three groups: control group(8 rats), kindling group(12 rats) and sham group(8 rats). All the rats were allowed to mate after one week's fully kindling. The pregnant rats in kindling group received electric stimulation every 48 h. Dams were allowed to deliver naturally. Effects of maternal seizure on the number of offspring, the survival rate and body weight of pups were observed. HE staining was used to visualize histopathological changes of placenta. Morris water maze test was used to assess the cognitive function and Nissal's staining to detect hippocampal morphology of the offspring. One-way ANOVA analysis and χ² test were used. Result: Compared with the sham group (95%(78/82)) and the control group (95%(82/86)), the survival rate of pups in kindling group(81%(66/82))was much lower (χ²=13.817, P=0.001). There were no significant differences in the number of pups per litter and pups birth-weight between kindling group and sham group or control group(F=0.312 and 0.257, P=0.736 and 0.776). HE staining showed that placental tissues from control and sham groups were normal whereas the histologic abnormalities of placentas from kindling group were characterized by thickening of the villus vascular walls, luminal stenosis, trophoblasts hyperplasia, abnormalities of trophoblasts with nuclear pyknosis and karyorrhexis and accumulation of inflammatory lymphocytes in labyrinthine zone. Nissl staining showed that neurons in hippocampus of P₀(0 d after birth) and P₈₄(84 d after birth) offspring from control and sham groups were normal, but neuronal damages were obvious in hippocampus of P₀ and P₈₄ offspring from kindling groups, and the damages in P₀ pups were severe with a marked loss of neuron, shrinkage of cells and nuclear pyknosis and karyorrhexis. In the Morris water maze, compared with the sham group ((29±8), (19±9), (10±4)s) and the control group ((25±6), (17±5), (14±4)s) rats in the kindling group ((36±8), (29±8), (30±11)s) exhibited significantly longer escape latency from the 3^rd, 4^th, and 5^th days (F=6.276, 7.518, 18.422, P=0.030, 0.003, 0.000), significant less time in the target quadrant ((27±8) vs.(58±11)and(68±13)s, F=35.993, P=0.000) and reduced number of crossing the platform ((4.4±1.7) vs. (7.2±1.6) and (8.5±1.3)times, F=18.377, P=0.000). In addition, there was no significant difference between control and sham groups(P all >0.05). Conclusion: The prenatal maternal seizures induced significant pathological damages to hippocampus and cognitive impairment of offspring. Hypoxia-ischemia of placenta might play an important role in this process.

Presence of autoantibodies against β1-adrenoceptor aggravates the kidney injury in rats

Since the autoantibodies against the second extracellular loop of β(1)-adrenoceptor (β(1)-AABs) have been found in the sera of patients with idiopathic dilated cardiomyopathy (IDCM), the involvement of autoimmune mechanisms in the pathogenesis of many cardiovascular diseases has extensively been investigated. Our previous study found that urinary occult blood and protein excretion were frequently found in the rats with positive β(1)-AABs, but the mechanisms are unclear. Therefore, we infused the β(1)-AABs into the vein periodically in an attempt to investigate whether β(1)-AABs could induce morphological and functional changes in the kidneys of adult and aged rats and explore the possible mechanisms. The synthetic peptide according to the sequences of the second extracellular loop of β(1)-adrenoceptor (β(1)-AR-ECII) was used to immunize the adult rats to acquire enough β(1)-AABs for use. Neonatal rat ventricular myocytes (NRVMs) culture was used to observe the biological effects of β(1)-AABs on the beating rate. The purified β(1)-AABs were transfused into the vein of rats. The sera level of blood urea nitrogen (BUN), creatinine (CR), uric acid (UA), urinary specific gravity, protein excretion, occult blood and urinary glucose were detected at the different time points by biochemistry and urine analyzers. HE and Masson's trichrome staining were used to detect the changes in kidney structure of passively immunized rats. Enhanced green fluorescent protein (EGFP) and β(1)-AR-EGFP plasmids were transfected into the human embryonic kidney 293 (HEK293) cells in order to observe the changes in cell injury with the treatment of β(1)-AABs. It was found that the sera level of BUN, CR and UA increased gradually and the ratio of BUN to CR decreased progressively with the administration of β(1)-AABs. The increasing of proteinuria, urinary occult blood and urinary glucose was detected by urine analyzer in β(1)-AABs group. By HE and Masson's coloration, lots of mononuclear cell infiltration and collagen fibers deposition could be observed at the 24th week of immunization. After the treatment of β(1)-AABs, the caspase-3 activity increased significantly in the HEK293 cells transfected with β(1)-AR-EGFP plasmids, while no significant changes were observed for lactate dehydrogenase (LDH) activity. The results indicate that long-term presence of β(1)-AABs can induce the morphological and functional damage of the kidneys in adult and aged rats.

[The up-regulation of hypoxia inducible factor-1α by hypoxic postconditioning reduces hypoxia/reoxygenation-induced injury in heart-derived H9c2 cells]

The aim of the present study was to explore the effects of hypoxic postconditioning (PostC) on heart-derived H9c2 cells injury induced by hypoxia/reoxygenation (H/R) and the expression of hypoxia inducible factor-1α (HIF-1α), and to analyze the relationship between them. Cultured H9c2 cardiac muscle cells were subjected to 3-hour hypoxia and 2-hour reoxygenation to simulate ischemia and reperfusion, or underwent 3 cycles of 5-min reoxygenation and 5-min hypoxia preceding the long reoxygenation to simulate ischemic postconditioning. Cell viability, lactate dehydrogenase (LDH) activity, and caspase-3 activity were detected respectively to investigate the cell injury induced by H/R. The level of HIF-1α mRNA was measured by real-time PCR. Western blot was used to determine HIF-1α protein level. The results showed that postconditioning significantly increased H9c2 cell viability, reduced the activity of LDH and caspase-3. Simultaneously, postconditioning up-regulated the HIF-1α protein level. Moreover, after DMOG, an inhibitor of proline hydroxylase (PHD) which targeted to HIF-1α degradation, was used to stabilize HIF-1α protein level, the reduction of H9c2 cells injury was comparable to that by postconditioning. There was a significant linear positive relationship between HIF-1α protein level and cell viability (r = 0.743, P < 0.01). After HIF-1α gene was silenced by siRNA, the cardio-protective effects of postconditioning was significantly weakened. These data suggest that up-regulation of HIF-1α plays an important role in the cardio-protection of postconditioning.

[The attenuation of myocardial susceptibility to ischemia/reperfusion injury by ischemic postconditioning in hypercholesteremia rats and the role of hypoxia inducible factor-1alpha]

OBJECTIVE

To explore whether ischemic postconditioning can attenuate the myocardial injury induced by ischemia/reperfusion (I/R) in hypercholesteremic rats and whether hypoxia inducible factor-1alpha (HIF-1alpha) play a role in the protection.

METHODS

Adult male Wistar rats received a high fat diet for 8 weeks to prepare the hypercholesteremic models. Myocardial damage induced by ischemia/reperfusion was evaluated by infarct size, creatine kinase (CK) activity and myocardial apoptosis. HIF-1alpha mRNA level was detected by real time-RT-PCR and the protein level was detected by Western blot.

RESULTS

Myocardial infarct size, CK activity, and caspase-3 activity induced by I/R were markedly increased in hypercholesteremic rats compared with those in normal rats. Ischemic postconditioning attenuated the myocardial injury in both normal rats and hypercholesteremic rats, and increased HIF-1alpha protein level. There was a significant linear inverse relationship between HIF-1alpha protein level and infarct size (r = -0.802, P <0.01).

CONCLUSION

Hypercholesteremia enhanced the susceptibility of myocardia to ischemia/reperfusion injury. While ischemic postconditioning markedly attenuated the increase of myocardial susceptibility to I/R induced by hypercholesteremia. HIF-1alpha might be one of the mechanisms of protection by ischemic postconditioning.

Microsatellite analysis of different ploidy offspring of artificial gynogenesis in Cyprinus carpio

Gynogenesis was induced by using UV-irradiated spermatozoa of blunt snout bream Megalobrama amblycephala to activate eggs of common carp Cyprinus carpio. The maternal genome was then duplicated by cold shock in 0 to 4° C cold water to retain the second polar body. Two kinds of fry, normal fry and abnormal tortuous fry, were hatched. Their DNA content was measured by flow cytometry. The normal fry were identified as diploid, representing the successful gynogenesis in C. carpio whereas the abnormal tortuous fry were haploid. Ten microsatellite loci were used to study the genetic diversity among C. carpio, diploid gynogenetic C. carpio and unduplicated haploid tortuous fry. The results indicated that the genetic homozygosity of gynogenetic C. carpio was significantly higher than that of C. carpio. The genetic homozygosity of the haploid C. carpio was intermediate between that of gynogenetic C. carpio and C. carpio. It might be easier for the allogenetic DNA fragments to be integrated into the haploid genome than into diploid gynogenetic genome.

Role of iNOS-derived reactive nitrogen species and resultant nitrative stress in leukocytes-induced cardiomyocyte apoptosis after myocardial ischemia/reperfusion

Polymorphonuclear leukocyte (PMN) accumulation/activation has been implicated as a primary mechanism underlying MI/R injury. Recent studies have demonstrated that PMNs express inducible nitric oxide synthase (iNOS) and produce toxic reactive nitrogen species (RNS). However, the role of iNOS-derived reactive nitrogen species and resultant nitrative stress in PMN-induced cardiomyocyte apoptosis after MI/R remains unclear. Male adult rats were subjected to 30 min of myocardial ischemia followed by 5 h of reperfusion. Animals were randomized to receive one of the following treatments: MI/R+vehicle; MI/R+L-arginine; PMN depletion followed by MI/R+vehicle; PMN depletion followed by MI/R+L-arginine; MI/R+1400 W; MI/R+1400 W+L-arginine and MI/R+ FeTMPyP. Ischemia/reperfusion-induced and L-arginine-enhanced nitrative stress and cardiomyocyte apoptosis were determined. PMN depletion virtually abolished ischemia/reperfusion- induced PMN accumulation, attenuated ischemic/reperfusion-induced and L-arginine-enhanced nitrative stress, and reduced ischemic/reperfusion-induced and L-arginine-enhanced cardiomyocyte apoptosis (P values all <0.01). Pre-treatment with 1400 W, a highly selective iNOS inhibitor, had no effect on PMN accumulation in the ischemic/reperfused tissue. However, this treatment reduced ischemia/reperfusion-induced and L-arginine-enhanced nitrative stress and cardiomyocyte apoptosis to an extent that is comparable as that seen in PMN depletion group. Treatment with FeTMPyP, a peroxynitrite decomposition catalyst, had no effect on either PMN accumulation or total NO production. However, treatment with this ONOO(-) decomposition catalyst also reduced ischemia/reperfusion-induced and L-arginine-enhanced nitrative stress and cardiomyocyte apoptosis (P values all <0.01). These results demonstrated that ischemic/reperfusion stimulated PMN accumulation may result in cardiomyocyte injury by an iNOS-derived nitric oxide initiated and peroxynitrite-mediated mechanism. Therapeutic interventions that block PMN accumulation, inhibit iNOS activity or scavenge peroxynitrite may reduce nitrative stress and attenuate tissue injury.

Autoantibody against cardiac beta1-adrenoceptor induces apoptosis in cultured neonatal rat cardiomyocytes

To clarify whether apoptosis is involved in the injury processes induced by autoantibody against cardiac beta1-adrenoceptor, we investigated the biological and apoptotic effects of antibodies on cultured neonatal rat cardiomyocytes. Wistar rats were immunized with peptides corresponding to the second extracellular loop of the beta1-adrenoceptor to induce the production of anti-beta1-adrenoceptor antibodies in the sera. Immunoglobulin (Ig) G in the sera was detected using synthetic antigen enzyme-linked immunosorbent assay and purified using the diethylaminoethyl cellulose ion exchange technique. Apoptosis of cardiomyocytes was evaluated using agarose gel electrophoresis and flow cytometry. Our results showed that the positive serum IgG greatly increased the beating rates of cardiomyocytes and showed an agonist-like activity. Furthermore, positive serum IgG induced cardiomyocyte apoptosis after treatment with beta1-adrenoceptor overstimulation for 48 h. The effects of monoclonal antibody against beta1-adrenoceptor were also found to be similar to those of positive serum IgG. It was suggested that the autoantibody could induce cardiomyocyte apoptosis by excessive stimulation of beta1-adrenoceptor.

Detection of serum autoantibodies against AT₁A-receptor during the development of the four types of hypertensive rat models

Using two-kidney one-clip renal hypertensive (2K1C group), stress-induced hypertensive (neural group), DOCA-salt treated hypertensive (DOCA group) and spontaneously hypertensive rats (SHR group), to investigate the change in AT(1A)-receptor autoantibodies (AT(1A)-AAs) during the development of the four types of hypertension. The biological activities of AT(1A)-AAs were examined. It was shown that the frequency of occurrence and titres of AT(1A)-AAs increased significantly during the development of hypertension. In the four hypertensive groups studied, the occurrence of AT(1A)-AAs was most prominent in SHR, 2K1C and neural groups. The biological effects of AT(1A)-AAs were shown to increase the beating frequency of cultured neonatal myocardial and vascular contractile tension. It is suggested that autoimmune mechanisms are involved the pathogenesis of different types of hypertension and the AT(1A)-AAs may be one of the mechanisms leading to cardiac hypertrophy.

Comparative studies of vasodilating effects of angiotensin-(1-7) on the different vessels

The purpose of this study was to compare the vasodilating effects of angiotensin-(1-7) [Ang-(1-7)] on the different vessels and to clarify its mechanisms by using relaxing responses of preconstricted vascular rings. The results showed: (1) Ang-(1-7) dose-dependently induced vasorelaxation in all the vessels studied. However, there is apparent heterogeneity in the responsiveness of vessels from different origin. (2) The Ang-(1-7)-induced vasorelaxation was endothelium dependent and largely mediated by NO system. (3) The vasodilator action of Ang-(1-7) was not mediated by AT1 or AT2 receptor subtypes. It is suggested that the Ang-(1-7)-induced vasorelaxation is endothelium dependent by some other unclarified angiotensin receptor subtypes and is largely mediated by NO system.

Changes in autoantibodies against beta1-adrenoceptor and M2-muscarinic receptor during development of renovascular hypertension in rats

In an experimental rat's renovascular hypertension model, we studied the genesis of anti-cardiac beta1-adrenoceptor and M2-muscarinic receptor autoantibodies in relation to the changes in immunological function during the development of renal hypertension. The biological activities of these autoantibodies were also examined. It was shown that after two weeks of operation both the frequency of occurrence and the titre of autoantibodies to cardiac beta1-adrenoceptor and M2-muscarinic receptor were significantly increased as compared with the control of pre-treatment. The increased autoantibodies lasted for several weeks and then automatically decreased gradually to the pre-clipping level at 10 weeks. Meanwhile the ratio of CD4+/CD8+ was also undergone an initial increase followed by gradual recovery and correlated well with the changes in antibody titre. The biological effects of these autoantibodies displayed an "gonistic-like" activities on the beating frequency of cultured neonatal cardiomyocyte. It is suggested that autoimmune mechanisms are involved in the pathogenesis of renal hypertension and the cardiac receptor autoantibodies might be one of the mechanisms leading to cardiac dysfunction.

[Effect of losartan on produce of sera autoantibodies to angiotensin II-1 receptor in renovascular hypertension rats]

AIM AND METHODS

The effects of losartan (after operation 2 week to 10 week, 5 mg/kg d ig) on generation of AT1R-AA in sera were observed during development of hypertension in rats. The renovascular hypertension (RVH) model was established by two-kidney one-clip method, a synthetic peptide corresponding to amino acid sequence 165-191 of the second extracellular loop of the angiotensin II-1 receptor (AT1R) was used as antigen, SA-ELISA were used to examine sera AT1R autoantibody (AT1R-AA).

RESULTS

The frequencies and titres of AT1R-AA after operation one week rats were significantly increased (P < 0.05). The treatment with losartan not only inhibited structural and functional changes, but also the frequencies and titres of AT1R-AA was significantly lower (P < 0.05) than RVH group.

CONCLUSION

It is suggested that the losartan significantly inhibits generation of the AT1R-AA.

Activated polymorphonuclear leukocytes induce cardiomyocyte apoptosis and the protective effects of carvedilol

Previous studies have shown that ischemia and reperfusion are potent stimuli for eliciting cardiomyocyte apoptosis, and that polymorphonuclear leukocytes (PMNs) are involved in the development of myocardial injury induced by ischemia and reperfusion. The present study examined whether PMN could directly induce cardiomyocyte apoptosis and, if so, it possible signal transduction pathways. In addition, we also investigated the effects of carvedilol, a potent antioxidant, on PMN-induced apoptosis. Cultured primary neonatal rat cardiomyocytes were exposed to PAF-activated PMNs at concentrations of 10(5), 3 x 10(5) and 10(6) cells/well for 48 h. Multiple detecting techniques, including electron microscopy, DNA gel electrophoresis. TUNEL assay and flow cytometry were used to identify myocyte apoptosis. All of these techniques demonstrated that activated PMNs directly induced cardiomyocyte apoptosis in a concentration-dependent manner, while unactivated PMNs showed no such effect. Activated PMN-induced apoptosis was partially inhibited by SB203580, a specific inhibitor of the p38-MAPK signaling system. Carvedilol (at a dose range of 1-10 mumol/l) significantly prevented activated PMN-induced cardiomyocyte apoptosis. These results suggest that PMNs, when activated, directly induce cardiomyocyte apoptosis and that the p38-MAPK signaling pathway might be involved in this process. Carvedilol may prevent PMN-induced apoptosis possibly because of its antioxidant properties.

[Changes in autoantibody against cardiovascular AT1-receptor during development of renovascular hypertension in rats]

The aim of this study was to observe the change in angiotensin II receptor subtype 1 (AT(1)) autoantibody during the development of renovascular hypertension (RVH). The Goldblatt renovascular hypertension model was established by the two-kidney one-clip method, and a synthetic peptide corresponding to amino acid sequence 165-191 of the second extracellular loop of the AT(1)-receptor was used as the antigen. Sera AT(1)-receptor autoantibody was detected by SA-ELISA. It was shown that two weeks after operation both the frequency of occurrence and the titre of autoantibodies to AT(1)-receptor were significantly increased as compared with the pre-treatment control. The increase in autoantibodies lasted several weeks and then decreased gradually to the pre-clipping level at 12 weeks. It is suggested that autoimmune mechanisms are involved in the pathogenesis of renovascular hypertension and the AT(1) autoantibodies may be one of the mechanisms leading to cardiac hypertrophy.

Protective effects of nitroglycerin-induced preconditioning mediated by calcitonin gene-related peptide in rat small intestine

Previous studies of myocardium have shown that ischemic preconditioning could be mimicked by nitroglycerin through stimulating the release of calcitonin gene-related peptide (CGRP). The present study examined whether nitroglycerin could also provide a preconditioning stimulus in the peripheral vascular bed (the anse intestinalis of rat), and whether endogenous CGRP is involved in this process. The model of in situ perfusion was prepared with rat small intestine. One hour of ischemia and 15 min of reperfusion caused a significant impairment of intestinal morphology and an increase in the release of both lactate dehydrogenase and malondialdehyde. Pretreatment with nitroglycerin, 10(-7), 3 x 10(-7), 10(-6) M for 5 min produced a significant improvement of intestinal tissue morphology and a decrease in the release of both lactate dehydrogenase and malondialdehyde. However, the protection afforded by nitroglycerin was abolished by CGRP-(8-37), a selective CGRP acceptor antagonist. Pretreatment with capsaicin, which specifically depletes the transmitter content of sensory nerves, also abolished the protection by nitroglycerin. In addition, the content of CGRP-like immunoreactivity in the effluent was increased during nitroglycerin perfusion. On the other hand, the results from the in vivo experiment showed that nitroglycerin (i.v. 0.13 mg/kg) injected 5 min before prolonged ischemia could provide significant protection against the injury caused by 30-min ischemia and 1-h reperfusion in the rat small intestine, but would also cause a significant increase in the levels of CGRP in the plasma. All these findings suggest that nitroglycerin-induced preconditioning is related to stimulation of CGRP release in the rat small intestine.

Insulin-like growth factor I inhibits cardiomyocyte apoptosis and the underlying signal transduction pathways

The effects of insulin-like growth factor I (IGF-I) on cardiomyocyte apoptosis induced by hypoxia in cultured neonatal rat cardiomyocyte were investigated. Primary neonatal rat cardiomyocytes were cultured in 95% N2-5% CO2 to imitate the in vivo hypoxic condition. Electron microscopic observation revealed a series of typical morphological changes characteristic of apoptosis in cardiomyocytes under the hypoxic condition. DNA gel electrophoresis showed DNA laddering in an ischemic duration-dependent manner. The hypoxia-induced cardiomyocyte apoptosis was also evidenced by flow cytometry and TUNEL assay. DNA gel electrophoresis showed that IGF-I in a dose range of 10(-9)-10(-7) mol/l could significantly prevent the hypoxia-induced cardiomyocyte apoptosis. The protective effects of IGF-I against hypoxia-induced apoptosis could also be verified by flow cytometry and TUNEL assay. A tyrosine kinase inhibitor (genistein), a MAPK inhibitor (PD-098059) and a P13 kinase inhibitor (wortmannin) could also suppress the antiapoptotic effects of IGF-I. These results suggest that IGF-I can directly alleviate the hypoxia-induced cardiomyocyte apoptosis and that the three kinase routes mentioned above may be involved in its signaling pathways.

[Effects of tetrahydroberberine on peripheral vascular dopamine DA1 and DA2 receptor subtypes]

OBJECTIVE

To study the effect of tetrahydroberberine (THB) on the peripheral vascular dopamine DA1 and DA2 receptors.

METHOD

Using isolated vascular rings method.

RESULT

THB(0.1-10 mumol.L-1) shifted the dose-response curves to the right in a nonparallel fashion and decreased the maximal response (Emax) of both the fenoldopam(FODA, a selective DA1 agonist)-induced and the propyl-butyl-dopamine(PBDA, a selective DA2 agonist)-induced vasorelaxation, showing a non-competitive antagonistic action. The pD'2 values of THB for FODA in the renal, pulmonary and mesenteric arteries were 5.29, 5.37 and 5.46, respectively, while for PBDA in the mesenteric and femoral arteries were 5.53 and 5.48, respectively. The potencies of this antagonistic action were weaker than those of SCH23390, a selective DA1 antagonist, domperidone, a selective DA2 antagonist and l-SPD, a mixed DA1/DA2 antagonist, domperidone, a selective DA2 antagonist and l-SPD, a mixed DA1/DA2 antagonist.

CONCLUSION

THB is a mixed peripheral DA, and DA2 receptor antagonist similar to l-SPD.

Effects of dopamine receptor agonists on the cAMP content in arteries of the rabbit

Effects of selective dopamine-1 (DA(1)) receptor agonist fenoldopam and dopamine-2 (DA(2)) receptor agonist propy1-butyl-dopamine (PBDA) on the cAMP generation system in renal, pulmonary, mesenteric and femoral arteries of rabbits were studied. The results are as follows. (1) Fenoldopam increased the cAMP production in a dose-dependent manner in pulmonary, renal and mesenteric arteries. This effect of fenoldopam was markedly blocked by specific DA(1) receptor antagonist SCH23390, but not at all by specific DA(2) receptor antagonist domperidone. (2) PBDA induced a dose-dependent decrease in cAMP content in femoral artery. However, the antagonist also moderately increased a dose-dependent cAMP production in mesenteric, pulmonary, and renal arteries. (3) Domperidone significantly decreased the inhibitory effect of PBDA on cAMP production in femoral artery, while it stimulated cAMP production in mesenteric artery but was of no effect on that in renal and pulmonary arteries. (4) SCH23390 had no effect on the inhibitory action of PBDA in decreasing cAMP content in femoral artery, while it markedly decreased the stimulatory action of PBDA on cAMP production in renal, pulmonary and mesenteric arteries. These findings suggest the presence of DA(1) receptors mediating the cAMP generation system in renal, pulmonary and mesenteric arteries, but only DA(2) receptors in femoral artery, and both DA1 and DA(2) receptors in mesenteric artery. PBDA inhibits the AC activity via stimulation of DA(2) receptors and increases the AC activity via stimulation of DA(1) receptors.

Inhibition of myocardial inward rectifier potassium current by propylbutyldopamine

AIM

To study the effects of propylbutyldopamine (PBDA) on the inward rectifier potassium current (Ik1).

METHODS

The quasi-steady state current-voltage relationship from the isolated guinea pig ventricular cells were measured using whole-cell patch-clamp techniques with a slow ramp depolarization (8 mV.s-1).

RESULTS

PBDA 5, 50, and 100 mumol.L-1 concentration-dependently reduced the inward rectifier potassium current. PBDA blocked Ik1 in guinea pig ventricular cells. The effect of PBDA was not blocked by the selective dopamine D2-receptor blocker, domperidone.

CONCLUSION

PBDA inhibited Ik1 directly, independent of the dopamine D2-receptor.

Screening of serum autoantibodies to cardiac beta1-adrenoceptors and M2-muscarinic acetylcholine receptors in 408 healthy subjects of varying ages

Autoantibodies to cardiac beta1-adrenoceptors and M2-muscarinic receptors have mainly been found in the sera of patients with idiopathic dilated cardiomyopathy (DCM). In order to elucidate the pathological significance of these autoantibodies in DCM, it is necessary to understand their characteristic distribution in a healthy population of different genders and ages. The peptides corresponding to the sequences of the second extracellular loops of the human beta1-adrenoceptor and M2-muscarinic receptors were therefore used as antigens to screen the sera of 408 healthy subjects of different ages (ranging from 0.5 to 85 years). Of 408 sera, 41 (10.0%) and 46 (11.3%) recognized the beta1-adrenoceptor and M2-muscarinic receptor peptides respectively. Of the positive sera for beta1-adrenoceptors and M2-muscarinic receptors, up to 63.4% and 56.5% had both anti-beta1-adrenoceptor and anti-M2-muscarinic receptor autoantibodies respectively. The antibody titres of the positive sera of healthy subjects were all of a low level, with a geometric mean titre of 1:42+/-1.9 for anti-beta1-adrenoceptor antibodies and 1:51+/-1.7 for anti-M2-muscarinic receptor antibodies. The frequency of occurrence of autoantibodies to both receptors in the sera of healthy subjects increased significantly with age. In conclusion, the autoantibodies to beta1-adrenoceptors and M2-muscarinic receptors in the sera of healthy subjects are characterized by a low frequency of occurrence and low titre, with the frequency of occurrence increasing with age.

Effects of norepinephrine and isopentenyladenosine on Na+/Ca2+ exchange currents in isolated guinea pig ventricular myocytes

AIM

To study the effects of norepinephrine (NE) and isopentenyladenosine (Iso) on Na+/Ca2+ exchange currents and the receptor mechanism.

METHODS

The quasi-steady state current-voltage relationship from the isolated guinea pig ventricular myocytes was measured using whole-cell voltage-clamp techniques with a ramp pulse protocol.

RESULTS

At potential of +50 mV, NE 0.005, 0.05, and 5 mumol.L-1 increased the Ni(2+)-sensitive current by 29% +/- 9%, 72% +/- 11%, and 124% +/- 31.4%, respectively; Iso 1.5, 150, and 1500 nmol.L-1 caused increases in the Ni(2+)-sensitive current by 2.8% +/- 2.8%, 56% +/- 13%, and 102% +/- 12%, respectively. Propranolol 10 mumol.L-1 completely inhibited the current changes induced by NE and Iso while phentolamine 50 mumol.L-1 showed no effects.

CONCLUSION

NE and Iso increased the Na+/Ca2+ exchange currents via stimulation of cardiac beta-adrenoceptor.

Effects of long-term application of dopamine HCl on dopamine agonist-induced cAMP production in rat renal cortex

AIM

To study the effects of long-term application of dopamine HCl (DA) on the functional changes of dopamine receptor subtypes coupled to adenyl cyclase in rat renal cortex.

METHODS

cAMP levels were measured by radioimmunoassay as an index of dopamine receptor function.

RESULTS

Injection of DA (30 mg.kg-1.d-1, i.p. 30 d) reduced the fenoldopam (Fen) (100 mumol.L-1)-induced increments of cAMP production from the control group of +1.26 +/- 0.04 to the DA-treated group of +0.63 +/- 0.22 nmol.min-1/g tissue and the propyl-butyl-dopamine (PBDA) (100 mumol.L-1)-induced decrements of cAMP production in the presence of Sch-23390 (Sch) from the control group of -0.38 +/- 0.18 to the DA-treated group of -0.11 +/- 0.08 nmol.min-1/g tissue with, however, comparable percentile changes for the 2 groups. Sch blocked both Fen- and PBDA-induced increase in cAMP production, while domperidone (Dom) blocked the decreasing effects of PBDA on cAMP accumulation in the presence of Sch.

CONCLUSION

Long-term application of DA produced a marked "down regulation" of both DA1 and DA2 receptors in rat renal cortex with, however, the responsiveness of the remaining receptors unchanged.

Localization of dopamine1A receptor mRNA in different vascular beds in rat: a nonradioactive in situ hybridization study

In situ hybridization of a biotin-labeled specific dopamine1A (D1A) receptor gene oligonucleotide probe combined with computer-assisted image analyzer was used to directly visualize D1A receptor mRNA and quantify the relative mRNA levels in sections of rat aorta and pulmonary and caudal arteries. Positive D1A receptor mRNA signals were found in rat aorta and pulmonary arteries, while no specific signals could be detected in the caudal artery. D1A receptor mRNA was located mainly within the medial layer of aorta, with intimal distribution in the pulmonary artery. The density of D1A receptor mRNA in different vascular beds demonstrated heterogeneity. D1A receptor mRNA levels in the aorta were much higher than those in the pulmonary artery (p < 0.01). These results demonstrate the existence of D1A receptor mRNA in both aorta and pulmonary beds, although with different distribution and density. The results further support the heterogeneity of the D1A receptor in different vascular beds.

Effects of dopexamine on heart function of isolated hypoxic rabbit heart and in comparison with fenoldopam and procaterol

AIM

To study the effects of dopexamine hydrochloride (Dop) on heart functions and coronary flow (CF) of normal and hypoxic isolated perfusing heart and compare the effects of Dop with those of fenoldopam hydrochloride (Fen) and procaterol hydrochloride (Pro).

METHODS

The isolated rabbit normal and hypoxic hearts were perfused with Krebs-Henseleit (K-H) solution via aorta at 37 +/- 0.5 degree C. The drug were added into the K-H solution.

RESULTS

Dop increased the CF, left ventricular contractile function (+ dp/dtmax etc) and heart rate (HR) in normal heart; Fen increased the heart function more potently, but increased the CF to a lesser degree than Dop did, whereas the effects of Pro was the least. In simple hypoxic group, at 30 min of perfusion, the + dp/dtmax and CF decreased by 66 +/- 4% and 48.1 +/- 1.0%, respectively. Dop remarkably attenuated the decreases in both CF and heart function during hypoxia as it decreased the + dp/dtmax by 32.0 +/- 2.4% and CF by 28 +/- 3%. Fen was less potent than Dop in attenuating the diminution of CF, while Pro was the least effective.

CONCLUSION

Dop has a better prospect in the treatment of ischemic heart disease in view of its dual action of increasing CF and inotropism.

Effects of dopexamine hydrochloride on calcium channels in isolated guinea pig ventricular myocytes

The mechanisms responsible for the cardiac positive inotropic effects of dopexamine hydrochloride, a combined dopamine receptor agonist at both D1-receptors and beta 2-adrenoceptors, were studied. The calcium channel currents were recorded using whole-cell patch clamp technique in isolated guinea pig ventricular myocytes. At a holding potential of -40 mV, cells were depolarized to 0 mV for 400 ms at a frequency of 0.2 Hz. Dopexamine hydrochloride at doses of 5, 50 and 100 microM increased the verapamil-sensitive Ca2+ inward current by 109, 147 and 194%, respectively. The effects of dopexamine hydrochloride on Ca2+ current reached its maximum at 5 min and partially recovered after washout of the drugs. The increased Ca2+ current induced by dopexamine hydrochloride was completely inhibited by 20 microM propranolol, a beta-adrenoceptor antagonist, and was not antagonized by 20 microM of SCH23390, a highly selective D1-receptor antagonist. These results suggest that the cardiac positive inotropic effects of dopexamine hydrochloride are brought about by the increase of Ca2+ current via stimulation of beta 2-adrenoceptors.

Effects of anti-peptide antibodies against human M2 muscarinic receptors on the cAMP generating system in guinea pig ventricles

The effects of anti-peptide antibodies (Ab) against the second extracellular loop of human muscarinic receptor-2 on the cAMP generating system in guinea pig ventricles were studied. These effects were compared with those of the muscarinic receptor agonist carbachol (Carb). It was shown that: (1) both Carb and Ab were able to inhibit the isoproterenol (Iso)-stimulated cAMP production of ventricles in a dose-dependent manner. Carb at 2 microM, 10 microM and 50 microM decreased Iso-stimulated cAMP production by 8.0 +/- 1.1, 15.8 +/- 1.2 and 28.4 +/- 1.7%, respectively; whereas Ab at 50 nM, 100 nM and 400 nM decreased it by 5.8 +/- 0.4, 16.8 +/- 1.4 and 30.6 +/- 2.5%, respectively. (2) Both Carb and Ab could also inhibit the basal cAMP content of ventricles significantly. Carb at 10 microM and Ab at 100 nM decreased it by 46.9 +/- 4.2% and 60.2 +/- 4.6%, respectively. (3) The inhibitory effects of both Ab and Carb on Iso-stimulated cAMP production were significantly prevented by atropine at 1.5 microM. (4) The inhibitory effect of Ab at 100 nM was almost completely abolished by the peptide (700 nM) used as immunogen. These findings suggest that the antibodies exhibit a stimulatory muscarinic activity similar to carbachol in the inhibitory modulation of cAMP production.

Comparison of the characteristics and density of dopamine-1 receptors in membranes from different arteries using [3H]SCH23390 binding

By using radioreceptor binding techniques and [3H]SCH23390 as a ligand, a comparative study was performed on the pharmacological properties and the density of dopamine-1 (D1) receptors in different vascular systems. [3H]SCH23390 was specifically bound to membranes from rabbit renal, mesenteric and pulmonary, but not femoral, arteries. The binding was saturable and in a manner consistent with the labeling of D1 receptors. The Kd value and Hill coefficient (nH) were similar in all three arteries with no statistically significant differences (p > 0.05) among them, indicating a homogenous binding site with a single class of high affinity. In competitive binding tests, the selective D1 antagonist and agonist inhibited the binding much more potently than the D2 antagonist, indicating a pharmacological characteristic of D1 receptors. The Bmax values, however, differed considerably among these arteries, with the value being the largest in the renal artery and smallest in the pulmonary artery. These findings are indicative of the existence of D1 receptor sites with identical properties but diverse density in different vascular beds, which underlies the relative functional importance of the receptors in regulating local blood flow in distinct vessels.

[Inhibitory effect of tocainide on calcium current and potassium current in guinea pig ventricular myocytes]

In whole cell voltage clamp experiment with isolated guinea pig ventricular myocytes, tocainide was shown to exhibit a concentration-dependent inhibition of calcium current (ICa) and delayed rectifier potassium current (IK). Tocainide with a therapeutic concentration of 50 mumol.L-1 significantly inhibited the ICa and Itail (deactivating tail current of IK) by 16% and 3% respectively. Inhibition of ICa by tocainide was also shown to be dependent upon stimulating frequencies, with a greater blockade occurring at 2.0 Hz (57%) than at 0.2 Hz (17%). Tocainide was found to inhibit the IK,ATP by 74% at 200 mumol.L-1 but not at 50 mumol.L-1. These inhibitory effects on ICa and IK can probably explain the therapeutic effect of tocainide on supraventricular tachycardia, and the shortening of plateau phase of action potential.

[Effects of dopexamine on the electrophysiologic changes during myocardial ischemia and comparison with fenoldopam and procaterol]

The effects of dopexamine (DPX), a new dopamine receptor agonist, on transmembrane potential and effective refractory period (ERP) of isolated guinea pig ventricular muscle superfused either with hypoxia or mimic ischemia perfusates were investigated by using intracellular microelectrode technique and compared with fenoldopam (FODA) and procaterol. DPX (3 x 10(-6) mol.L-1) was found to significantly reduce both the extent of decrease of resting potential, action potential amplitude and maximal upstroke velocity and the degree of shortening of action potential duration caused by hypoxia or ischemia. These effects of DPX were significantly greater than those of FODA and procaterol albeit the latter showed effects similar to DPX. DPX could not only lengthen the abbreviated ERP resulting from hypoxia, but also shorten the prolonged ERP caused by ischemia. This action of DPX was more evident than that of FODA and procaterol. The results reveal the potential advantages of DPX over other dopaminergic agonists in the antiarrhythmic activity during myocardial ischemia.

Comparison of the effects of dopamine1- and dopamine2-receptor agonists on the cAMP generating system in canine coronary and renal arteries

To further evaluate the functional significance of dopamine (DA) receptors in different vasculature, in this study we compared the effects of D1- and D2-receptor agonists on canine coronary and renal arteries by measuring adenylate cyclase (AC) activity as a biomedical index of DA receptor function. It was found that both the selective D1-receptor agonist, fenoldopam, and the D2-receptor agonist, propyl-butyl-dopamine (PBDA), induced a dose-related increases in cAMP formation in coronary and renal arteries; however, the magnitude of increase in the renal artery was remarkably greater than that in the coronary artery. The stimulatory effect on AC activity of fenoldopam was significantly more potent than that of PBDA. The selective D1-receptor antagonist, SCH23390, blocked fenoldopam- and PBDA-induced cAMP production, while the selective D2-receptor antagonist, domperidone, was without effect on the increase of cAMP elicited by PBDA. After beta-adrenergic blockade with propranolol, fenoldopam still increased the cAMP level significantly but to a much lesser degree. The existence of postsynaptic D2-receptor associated with inhibition of cAMP formation could not be demonstrated in this study. These data suggest the presence of D1-receptors associated with stimulation of AC activity in both renal and coronary arteries. However, there are much fewer receptor sites in the coronary artery than in the renal artery, suggesting less physiological importance of such receptors in the coronary artery than in the renal artery.

Comparison of dopexamine hydrochloride, fenoldopam, and procaterol on myocardial nutritional flow in rats

Myocardial nutritional flow (MNF) was determined using 99mTechnetium-methoxy-isobutyl-isonitrile (99mTc-MIBI) in rats. At 25 nmol.kg-1, dopexamine hydrochloride (DH), fenoldopam, and procaterol increased the uptake rate of 99mTc-MIBI/g myocardium by 80.8 +/- 10.2% (P < 0.01), 44.9 +/- 6.3% (P < 0.05), and 30.2 +/- 5.4% (P < 0.05) respectively. These findings suggested the potential advantages of DH over other dopaminergic agonists in the treatment of coronary disease.

Contribution of extravascular compression to reduction of maximal coronary blood flow

Effects of ventricular compression on maximally dilated left circumflex coronary blood flow were investigated in seven mongrel dogs under pentobarbital anesthesia. The left circumflex artery was perfused with the animals' own blood at a constant pressure (63 mmHg) while left ventricular pressure was experimentally altered. Adenosine was infused to produce maximal vasodilation, verified by the hyperemic response to coronary occlusion. Alterations of peak left ventricular pressure from 50 to 250 mmHg resulted in a linear decrease in total circumflex flow of 1.10 ml.min-1 x 100 g heart wt-1 for each 10 mmHg of peak ventricular to coronary perfusion pressure gradient; a 2.6% decrease from control levels. Similar slopes were obtained for systolic and diastolic flows as for total mean flow, implying equal compressive forces in systole as in diastole. Increases in left ventricular end-diastolic pressure accounted for 29% of the flow changes associated with an increase in peak ventricular pressure. Doubling circumferential wall tension had a minimal effect on total circumflex flow. When the slopes were extrapolated to zero, assuming linearity, a peak left ventricular pressure of 385 mmHg greater than coronary perfusion pressure would be required to reduce coronary flow to zero. The experiments were repeated in five additional animals but at different perfusion pressures from 40 to 160 mmHg. Higher perfusion pressures gave similar results but with even less effect of ventricular pressure on coronary flow or coronary conductance. These results argue for an active storage site for systolic arterial flow in the dilated coronary system.

Effects of dopamine D1 and dopamine D2 receptor agonists on coronary and peripheral hemodynamics

This study evaluated the coronary dopamine receptors by using the dopamine D1 receptor agonist fenoldopam, dopamine D2 receptor agonist propylbutyldopamine, and their selective antagonists SCH23390 and domperidone. Left circumflex coronary flow (CF), coronary perfusion pressure at constant flow, left ventricular hemodynamics, and total peripheral vascular resistance (TPR) were measured in pentobarbital-anesthetized dogs at constant arterial pressures. At doses of 200, 500 and 5000 nM, both fenoldopam and propylbutyldopamine induced dose-related inotropic effects, as evidenced by maximal dp/dt and cardiac output, an increase in CF, decrease in coronary vascular resistance and a decrease in TPR. Fenoldopam was more potent in its cardiac and coronary effects while propylbutyldopamine was more potent peripherally. On the basis of dosage used, the positive inotropic effects of fenoldopam and propylbutyldopamine were much weaker than dopamine. After beta-receptor blockade, the inotropic and coronary effects of fenoldopam and propylbutyldopamine were extremely attenuated. Domperidone could largely antagonize the propylbutyldopamine-induced inotropic and coronary effects while SCH23390 showed no significant effect. In addition, under our experimental conditions, the fenoldopam- and propylbutyldopamine-induced decreases in TPR were markedly reduced by SCH23390 and domperidone, respectively. The results indicate that the coronary effects of fenoldopam and propylbutyldopamine result not from a primary coronary vasodilating action, but from vasodilation secondary to positive inotropic effects. Both dopamine D1 and dopamine D2 receptors are involved in the peripheral vascular hemodynamics.

Cocaine depresses the canine myocardium

The effects of cocaine hydrochloride infusion on left ventricular function in the anesthetized dog were observed under controlled heart rate and blood pressure conditions. In every case an immediate decrease in performance, as evidenced by maximal + rate of change of ventricular pressure (dP/dt), occurred and was a linear function of cumulative dose. Maximal (-) dP/dt also declined, indicating a decreased rate of ventricular relaxation. Right atrial and left ventricular end diastolic pressure increased, with no change in cardiac output or cardiac work, whereas coronary flow decreased slightly. This small decrease in coronary flow was probably related to the decrease in contractile vigor rather than a direct effect of cocaine on vascular tone. Although plasma norepinephrine concentration initially increased, ventricular function did not increase and continued to decline with cumulative cocaine dose. Tissue norepinephrine levels measured in isolated heart-lung preparations were not depleted. These findings indicate a direct toxic action of cocaine on the myocardium, decreasing both contractile performance and relaxation state. Plasma cocaine levels were constant during continuous infusion of the drug, indicating that the progressive toxicity observed did not result from increased circulating cocaine.

[Changes in platelet aggregation and coronary collateral circulation during the early phase of myocardial ischemia in dogs]

Experiments were performed on 18 anesthetized open-chest dogs to observe the changes in platelet aggregation and coronary collateral circulation during the early phase of acute myocardial ischemia. An increase in platelet aggregation rates (PAgR) and a decrease in platelet counts (PC) were found in the blood collected from the ischemic myocardium after coronary occlusion. PAgR was increased by 58.7 +/- 5.6% and PC was reduced by 39.5 +/- 23.6% at 50 min after occlusion (P less than 0.01). Under the condition of controlling aortic blood pressure, collateral coronary vascular capacity (CVC) was not changed (P greater than 0.05), but the effective collateral coronary flow to the ischemic zone, calculated by Wyatt et al's equation, was significantly reduced by 23.5 +/- 9.7% at 50 min after occlusion (P less than 0.05). There was a negative correlation between the changes in PAgR and the effective collateral coronary flow ( r = -0.857, P less than 0.01), and between the collateral indices and infarct size (r = -0.847, P less than 0.01). Abnormal changes in parameters of platelet and coronary collateral circulation after myocardial ischemia were nearly abolished by intravenous injection of aspirin before coronary occlusion. The results suggest that the deleterious changes of platelet aggregation during the early phase of the acute myocardial ischemia may decrease the effective collateral coronary flow significantly and thereby enlarge the infarct size.