Dihydroergotamine ameliorates liver fibrosis by targeting transforming growth factor β type II receptor

BACKGROUND

The transforming growth factor β (TGFβ) signaling pathway plays a crucial role in the development of liver fibrosis by activating TGFβ type II receptor (TGFβR2), followed by the recruitment of TGFβR1 finally triggering downstream signaling pathway.

AIM

To find drugs targeting TGFβR2 that inhibit TGFβR1/TGFβR2 complex formation, theoretically inhibit TGFβ signaling pathway, and thereby ameliorate liver fibrosis.

METHODS

Food and Drug Administration-approved drugs were screened for binding affinity with TGFβR2 by virtual molecular docking. We identified 6 candidates and further explored their potential by Cell Counting Kit-8 (CCK-8) cell cytotoxic experiment to validate toxicity and titrated the best cellular working concentrations. Next, we further demonstrated the detailed molecular working mechanisms using mutagenesis analysis. Finally, we used a mouse model to investigate its potential anti-liver fibrosis effect.

RESULTS

We identified 6 drug candidates. Among these 6 drugs, dihydroergotamine (DHE) shows great ability in reducing fibrotic gene expressions such as collagen, p-SMAD3, and α-SMA in TGFβ induced cellular model of liver fibrosis in LX-2 cells. Furthermore, we demonstrated that DHE binds to TGFβR2. Moreover, mutation of Leu27, Phe30, Thr51, Ser52, Ile53, and Glu55 of TGFβR2 disrupted the binding of TGFβR2 with DHE. In addition, DHE significantly improved liver fibrosis, as evidenced by Masson’s trichrome staining of liver sections. This is further supported by the width and the velocity of the portal vein, and serum markers of liver function. In line with those observations, DHE also decreased macrophages infiltration and extracellular matrix deposition in the liver.

CONCLUSION

DHE alleviates liver fibrosis by binding to TGFβR2 thereby suppressing TGFβ signaling pathway. We show here that as far as drug repurposing, DHE has great potential to treat liver fibrosis.

Population genomics reveals that natural variation in PRDM16 contributes to cold tolerance in domestic cattle

Environmental temperature serves as a major driver of adaptive changes in wild organisms. To discover the mechanisms underpinning cold tolerance in domestic animals, we sequenced the genomes of 28 cattle from warm and cold areas across China. By characterizing the population structure and demographic history, we identified two genetic clusters, i.e., northern and southern groups, as well as a common historic population peak at 30 kilo years ago. Genomic scan of cold-tolerant breeds determined potential candidate genes in the thermogenesis-related pathways that were under selection. Specifically, functional analysis identified a substitution of PRDM16 (p.P779L) in northern cattle, which maintains brown adipocyte formation by boosting thermogenesis-related gene expression, indicating a vital role of this gene in cold tolerance. These findings provide a basis for genetic variation in domestic cattle shaped by environmental temperature and highlight the role of reverse mutation in livestock species.

[The expression and significance of TRPM8 among chronic rhinosinusitis with nasal polyps]

Objective: To compare the expression and difference of melastatin-related transient receptor potential 8(TRPM8) among chronic rhinosinusitis, nasal polyps and normal mucosa tissues. And to explore the significant expression of TRPM8 among CRSwNP. Methods: Fifty-one patients underwent endoscopic sinus surgery in the Department of Otorhinolaryngology Head and Neck Surgery of Renmin Hospital of Wuhan University from February 2019 to January 2020 were recruited, including 33 males and 18 females, aged from 14 to 65 years old (34.55±1.689).Immunohistochemistry was used to detected the expression of TRPM8 protein among CRSsNP(17),CRSwNP (17) and control tissuses(17). In addition, the correlation between the expression of TRPM8 protein in CRSwNP patients and preoperative CT Lund-Mackay scores and preoperative VAS scores and sinonasal outcome test-20 scores was analyzed, respectively. The primary human nasal epithelial cells were cultured in vitro and the expression of TRPM8 was detected by quantitative real-time PCR and western blotting. The tissue in control group, chronic rhinosinusitis without nasal polyps (CRSsNP) group and the CRSwNP group were collected and grinded into tissue homogenized. The expression of TRPM8 protein was detected by western blotting after 24 h stimulation after homogenate was added into the medium of RPMI 2650 and primary nasal epithelial cells. Results: Compared with the control, the expression of TRPM8 was significantly up-regulated in nasal polyps (t=6.852, P<0.05). TRPM8 was mainly expressed in epithelial cells. The expression of TRPM8 in the epithelial cells of CRSsNP had no difference with the control group (t=1.980, P>0.05). In addition, the expression of TRPM8 in CRSwNP patients was positively correlated with the preoperative CT Lund-Mackay scores and VAS scores and SNOT-20 scores (r=0.512, P<0.05;r=0.853, P<0.01;r=0.814, P<0.01). After cultured primary epithelial cells in vitro, the expression level of TRPM8 in epithelial cells derived from nasal polyp was significantly higher than that in control group (t=8.845, P<0.05). By adding the homogenization of control and CRSsNP and CRSwNP tissues, the expression of TRPM8 in RPMI 2650 cells and primary nasal epithelial cells was changed and that was significantly increased after adding the homogenization of the group of CRSwNP. Conclusion: TRPM8 is highly expressed in nasal polyps epithelial cells, suggesting that TRPM8 may be involved in the pathogenesis of nasal polyps regulated by nasal epithelial cells.

[Practice guideline for patients with osteoporosis]

In recent years, osteoporosis (OP) has become one of the main diseases affecting the health of middle-aged and elderly people in China, and the prevalence of OP has increased significantly. The clinical diagnosis and treatment guidelines for this disease are also constantly updated. The overall principles speciallyemphasise that doctors and patients need to work together to negotiate the details of the diagnosis and treatment guidelines, in order to improve the OP clinical diagnosis and treatment rate. Therefore, patients' knowledge of the disease, understanding of clinical guidelines, and cooperation with doctors to implement diagnosis and treatment plans are very important. In this study, from the most concerned issues of the patients, we established the OP patient practice guideline working group. 14 recommendations, as the OP patient practice guidelines, are proposed in accordance with the relevant principles of the "World Health Organization guidelines development manual" and the international normative process.

[Clinical analysis of FRAX in the assessment of fracture risk in patients with rheumatic disease in three medical center]

Objective: The aim is to analyze the fracture risk in rheumatic patients by fracture risk assessment tool (FRAX), which is recommended by World Health Organization (WHO), so that we can prevent the occurrence of osteoporotic fracture earlier. Methods: Totally 617 participants, 204 out-patients with rheumatism, 204 in-patients with rheumatism and 209 healthy controls, from March to October in 2018 of Fourth Medical Center of PLA General Hospital, Jishuitan Hospital and China-Japan Friendship Hospital, were enrolled in this study. The probability of hip fracture (PHF) and major osteoporotic fracture (PMOF) in 10 years with FRAX were compared, and the differences between taking sleroids or not and with or without bone mass density (BMD) of femoral neck were evaluated. Correlation analysis was conducted between PHF, PMOF and clinical information, including age, disease duration, gender, steroid usage, osteocalcin, P1NP and β-crosslaps. Results: There was no significant difference in PMOF within 10 years (3.455±2.690 vs 2.973±2.149 vs 3.323±1.828) among the three groups (P>0.05), but the PHF (0.986±1.619 vs 0.515±0.873 vs 0.149±0.311) was different (P<0.05). PHF and PMOF increased gradually with age. PMOF of patients without glucocorticoid therapy in 10 years was lower than that of patients with glucocorticoid (3.554±2.584 vs 2.857±2.238, P<0.05). There is no difference between the results of FRAX calculated with BMD or not (3.012±2.231 vs 3.207±2.601, P>0.05). PHF and PMOF were positively correlated with age, course of disease, glucocorticoid use and osteocalcin level, while PHF was negatively correlated with TP1NP among in-patients. Conclusion: The prevalence of 10-year hip fracture calculated by FRAX in rheumatism patients is higher than that of healthy group. FRAX can be used to calculate fracture risk without BMD. Combination of FRAX and bone turnover markers may be more effective in prediction of osteoporotic fracture in rheumatic patients.

[Comparison of disease activities and extent measurements for anti-neutrophil cytoplasmic autoantibody-associated vasculitis]

OBJECTIVE

To investigate the significance of a set of seven disease activities and extension measurements and their correlations between one and another for anti-neutrophil cytoplasmic autoantibody associated vasculitis (AAV).

METHODS

A total of 121 patients from Peking University International Hospital and Fouth Medical Center of PLA General Hospital with confirmed diagnoses of AAV clinically were enrolled in the study, including 15 cases of eosinophilic granulomatous with polyangiitis (EGPA), 59 cases of granulomatous with polyangiitis (GPA) and 47 cases of microscopic polyangiitis (MPA). A hundred and twenty-one AAV patients were divided into death group and survival group according to their survival conditions. A set of seven disease assessment scales including Birmingham vasculitis activity score (BVAS)-1994, BVAS-2003, as well as BVAS/GPA, vasculitis damage index (VDI), disease extent index (DEI), five factor score (FFS)-1996, and FFS-2009 were measured and scored one by one, and their relationships which were represented by Spearman correlation coefficient were compared between one and another.

RESULTS

BVAS-1994, BVAS-2003, as well as BVAS/GPA, VDI, DEI, and FFS, all of those seven evaluation indexes of the AAV patients in the death group were significantly higher than those in the survival group (P<0.05). Except for BVAS/GPA, all those above indicators in the patients with EGPA were lower than those in the patients with GPA and those in the patients with MPA, and those in all of the AAV patients as a whole group. There were high correlations among BVAS-2003, BVAS-1994 and BVAS/GPA (r values were 0.9 and 0.7, respectively); BVAS-1994 was fairly correlated with BVAS/GPA (r=0.69); FFS-1996 and FFS-2009 were highly correlated (r=0.73) with each other; BVAS-1994, BVAS-2003 and BVAS/GPA were fairly correlated with DEI (with r values of 0.62, 0.65, and 0.62, respectively); VDI was also fairly correlated with BVAS-1994 and with BVAS-2003 (r values were 0.49 and 0.52, respectively).

CONCLUSION

All of those seven AAV assessment indicators above can be used as indicators of disease activity and prognosis in AAV patients, most of which were relevant within one and another. There were high correlations among BVAS-2003, BVAS-1994 and BVAS/GPA, and besides, there were also high correlations between FFS-1996 and FFS-2009.

[Comparison of Dengue viral nonstructural protein 1 antigen testing kits]

Objective: To investigate the sensitivity and specificity of commercial nonstructural protein 1 (NS1) testing kits for Dengue fever diagnose, and provide the evidence for diagnostic criteria revision. Methods: 300 PCR or virus isolation positive blood samples for dengue virus were collected from sentinel hospitals for dengue surveillance in Guangzhou, Dongguang and Zhongshang from May 2015 to Nov. 2016. At the same time, 308 PCR negative samples for Dengue virus were collected as control group. The information of the sample was collected using questionnaires. These samples were tested using imported and domestic ELISA and the colloidal gold-labeled kits that were widely used for detecting dengue NS1. Sensitivity, specificity and coincidence were calculated and analyzed, and Z hongshan's result was regarded as the reslut of the third part. Results: The positive group includes 133 males and 167 females, average ages are 47.2±13.3, 179, 110 and 11 of them is Dengue Ⅰ, Ⅱ and Ⅲ respectively. The negative group includes 154 males and 154 females, average ages are (40.1±11.6) years old. The sensitivity of domestic ELISA Kits (94.5%) is less than imported (99.5%), and the result has statistical significance (χ(2)=8.59, P=0.030), the specificity is 99.7% and 97.7% respectively; The sensitivity of imported and domestic the colloidal gold-labeled Kits is 97.5% and 96.5% respectively, both of specificities are 100%. The sensitivity and specificity of Dengue Ⅰ for NS1 test are more than 97.0%. The sensitivity of domestic ELISA and gold-labeled Kits is 90.0% and 95.0%, and the specificity is 96.8% and 100% respectively for Dengue Ⅱ test. The sensitivity of imported ELISA and gold-labeled Kits is 100% and 98.0%, and the specificity is 99.4% and 100% respectively for Dengue Ⅱ test. The result of the third party show the sensitivity and specificity of domestic ELISA and gold-labeled Kits are 90.0% and 98.0%, the differences has statistical significance (χ(2)=5.67, P=0.020). Conclusion: NS1 testing can be used as early dengue fever diagnose for higher sensitivity and specificity.

[The clinical analysis of 46 cases with antineutrophil cytoplasmic antibody-associated vasculitis]

OBJECTIVE

To investigate the clinical features of patients with antineutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV), and to explore the disease activity of AAV patients and the relationship with prognosis.

METHODS

The clinical data of 46 cases of AAV patients in the First Affiliated Hospital of PLA General Hospital were analyzed retrospectively.The clinical and laboratory features of each clinical subtype were compared.The disease activity of AAV and the relationship between disease activity and prognosis were evaluated.

RESULTS

Among the 46 patients with AAV, 24 were male, and 22 were female, with the average age of 56±18.Among the subtypes of AAV, the number of granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA) were 22, 17 and 4 respectively, while the positive rate of ANCA are 72.7%, 88.2% and 50.0% respectively.For GPA, the results of ANCA were mainly C-ANCA or ANCA directed toward proteinase-3 (PR3), and for MPA, the results of ANCA were mainly P-ANCA or ANCA directed toward myeloperoxidase (MPO). Upper and lower respiratory disease, renal involvement and non-deformity arthropathy were the common clinical manifestations of all primary AAV subtypes.Epistaxis, nasal blood scab, saddle nose, pulmonary nodule and intrapulmonary cavities were the characteristic manifestations of GPA, while rapid progress of renal failure was prominent in MPA.Whatever their ANCA results, there were no significant differences between each other as to system-organ involvements and laboratory indexes.Seven patients (15.2%) died during hospitalization or in follow-up visits.Serious involvements of heart, lung, kidney, and complicated with infections were the main risk factors of death in AAV patients.

CONCLUSIONS

Upper and lower respiratory involvements and kidney diseases are the primary manifestations of AAV patients.ANCA results are irrelevant with disease activity and system-organ involvements.Serious involvements of heart, lung, kidney, and complicated with infections are the main risk factors of death in AAV patients.

Evaluating the annotation of protein-coding genes in bacterial genomes: Chloroflexus aurantiacus strain J-10-fl and Natrinema sp J7-2 as case studies

Gene annotation plays a key role in subsequent biochemical and molecular biological studies of various organisms. There are some errors in the original annotation of sequenced genomes because of the lack of sufficient data, and these errors may propagate into other genomes. Therefore, genome annotation must be checked from time to time to evaluate newly accumulated data. In this study, we evaluated the gene density of 2606 bacteria or archaea, and identified 2 with extreme values, the minimum value (Chloroflexus aurantiacus strain J-10-fl) and maximum value (Natrinema sp J7-2), to conduct genome re-annotation. In the genome of C. aurantiacus strain J-10-fl, we identified 17 new genes with definite functions and eliminated 34 non-coding open-reading frames; in the genome of Natrinema sp J7-2, we eliminated 118 non-coding open reading frames. Our re-annotation procedure may provide a reference for improving the annotation of other bacterial genomes.

Clinical features and outcome of neuropsychiatric lupus in Chinese: analysis of 240 hospitalized patients

Neuropsychiatric (NP) events are severe manifestations of systemic lupus erythematosus (SLE) and relate to poor outcome. The aims of this study are to investigate the NP manifestations of SLE and to identify the predictive factors for clinical outcome. There was a retrospective review of 240 hospital patients with primary NP events of SLE (NPSLE) from 1990 to 2004. Neuropsychiatric manifestations, SLE disease activity index (SLEDAI) score, System lupus International Collaborating Clinic/American College of Rheumatology Damage Index (SLICC/ACR-DI) score, magnetic resonance imaging (MRI) findings, treatment and mortality rate were included for analysis. From this group of patients, 15 NP syndromes were identified. The most frequent manifestation was headache, followed by seizure. The mean SLEDAI and SLICC/ACR-DI scores were 19.9 +/- 6.9 and 3.5 +/- 1.6, respectively. Abnormal MRI features were found in 67% (61/91) patients. At least one intrathecal (IT) injection of methotrexate (MTX) plus dexamethasone (DXM) was administered to 109 (45.4%) patients. High dose (1 g) intravenous methylprednisolone pulse therapy (IVMP) was administered to 167 (69.5%) patients. Multifactor analysis revealed that high SLICC/ACR-DI scores and sets of concurrent NP symptoms were independently associated with poor outcome, whereas pulse IVMP and IT injection of MTX plus DXM were protective factors against poor outcome. From our data, NPSLE is heterogeneous and is usually associated with high disease activity and organ damage scores. High SLICC/ACR-DI score and having more than two sets of NP symptoms are the predictors for poor outcome, whereas pulse IVMP and IT injection of MTX plus DXM can improve the prognosis.

[Detection of plasma urokinase-type plasminogen activator and its receptor in acute or chronic hepatitis B patients and its clinical significance.]

BACKGROUND

To study the expression of plasma uPA and uPAR in Acute or Chronic Hepatitis B patients, to investigate changes of blood fibrinolytic system in Hepatitis B and its clinical significance.

METHODS

The level of detected plasma urokinase-type plasminogen activator (uPA) and urokinase-type plasminogen activator receptor (uPAR) were measured by Enzyme Linked Immuno Sorbent Assay (ELISA).

RESULTS

The levels of plasma uPA and uPAR were significantly higher in patients with Acute or Chronic Hepatitis B than that of control group (P less than 0.05, P less than 0.01), and also higher in serious group than that of non-serious group of Chronic Hepatitis B patients (P less than 0.05), and also higher in chronic group than in acute group (P less than 0.05). The level of plasma uPAR was significantly higher in patients with serious jaundice than that of non-serious jaundice group (P less than 0.01). The levels of uPA and uPAR are significantly higher in acute period than that in recover period of Acute Hepatitis B patients, but the levels in recover period is also higher than that in control group. The level of plasma uPAR have positive correlation with prothrombin (PT), international normalized ratio (INR) and total bilirubin (P less than 0.01).

CONCLUSION

The level of plasma UPA nad UPAR were enhanced in Acute or Chronic Hepatitis B patients was related with the degree of inflammation, was also related with high expression of serious damage of liver cell. It may be one of important cause to imbalance between coagulation and fibrinolytic in hepatitis.

Studies on the inactivation of bovine liver enoyl-CoA hydratase by (methylenecyclopropyl)formyl-CoA: elucidation of the inactivation mechanism and identification of cysteine-114 as the entrapped nucleophile

The inhibitory properties of (methylenecyclopropyl)formyl-CoA (MCPF-CoA), a metabolite derived from a natural amino acid, (methylenecyclopropyl)glycine, against bovine liver enoyl-CoA hydratase (ECH) were characterized. We have previously demonstrated that MCPF-CoA specifically targets ECHs, which catalyze the reversible hydration of alpha,beta-unsaturated enoyl-CoA substrates to the corresponding beta-hydroxyacyl-CoA products. Here, we synthesized (R)- and (S)-diastereomers of MCPF-CoA to examine the stereoselectivity of this inactivation. Both compounds were shown to be competent inhibitors for bovine liver ECH with nearly identical second-order inactivation rate constants (k(inact)/K(I)) and partition ratios (k(cat)/k(inact)), indicating that the inactivation is nonstereospecific with respect to ring cleavage. The inhibitor, upon incubation with bovine liver ECH, labels a tryptic peptide, ALGGGXEL, near the active site of the protein, where X is the amino acid that is covalently modified. Cloning and sequence analysis of bovine liver ECH gene revealed the identity of the amino acid residue entrapped by MCPF-CoA as Cys-114 (mature sequence numbering). On the basis of gHMQC (gradient heteronuclear multiple quantum coherence) analysis with [3-(13)C]-labeled MCPF-CoA, the ring cleavage is most likely induced by the nucleophilic attack at the terminal carbon of the exomethylene group (C(2)'). We propose a plausible inactivation mechanism that involves relief of ring strain and is consistent with examples found in the literature. In addition, these studies provide important clues for future design of more efficient and selective inhibitors to control and/or regulate fatty acid metabolism.

Ladder operator for the one-dimensional Hubbard model

The one-dimensional Hubbard model is integrable in the sense that it has an infinite family of conserved currents. We explicitly construct a ladder operator which can be used to iteratively generate all of the conserved current operators. This construction is different from that used for Lorentz invariant systems such as the Heisenberg model. The Hubbard model is not Lorentz invariant, due to the separation of spin and charge excitations. The ladder operator is obtained by a very general formalism which is applicable to any model that can be derived from a solution of the Yang-Baxter equation.

Swelling-activated chloride currents in embryonic chick heart cells

AIM

To characterize a swelling-activated chloride current, I(Cl, swell), in white Leghorn chick heart cells and the effects of chlorpromazine (CPZ) effects.

METHODS

The patch-clamp technique in the whole-cell configuration was used.

RESULTS

Hyposmotic swelling elicited I(Cl, swell) in white Leghorn chick heart cells. The current amplitude increased from (452 +/- 200) pA to (849 +/- 373) pA with a reduction of osmolarity from 300 mmol.L-1 to 270 mmol.L-1, 4',4-Diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) 100 mumol.L-1 decreased I(Cl, swell) from (1196 +/- 505) pA to (830 +/- 328) pA in hyposmotic solution. In white Leghorn chick heart cells I(Cl, swell) was not induced by CPZ 30 mumol.L-1, which is different from the case of E coli spheroplast.

CONCLUSION

Swelling-activated chloride current was activated by hyposmotic swelling in white Leghorn chick heart cells. The mechanism for activating the current is different from that of mechanosensitive ion channels of E coli.

4-aminopyridine, a specific blocker of K(+) channels, inhibited inward Na(+) current in rat cerebellar granule cells

The effects of 4-aminopyridine (4-AP), a specific blocker of outward K(+) current, on voltage-activated transient outward K(+) current (I(K(A))) and inward Na(+) current (I(Na)) were investigated on cultured rat cerebellar granule cells using the whole cell voltage-clamp technique. At the concentration of 1-5 mM, 4-AP inhibited both I(K(A)) and I(Na). It reduced the amplitude of peak Na(+) current without significant alteration of the steady-state activation and inactivation properties. The inhibitory effect was not enhanced by repeated depolarizing pulses (0.5 or 0.1 Hz), suggesting that the binding affinity of 4-AP on Na(+) channels is state-independent. In contrast, the effect of 4-AP on Na(+) channels appeared to be voltage-dependent, the weaker inhibition occurred at more depolarization. Moreover, 4-AP slowed both the activation and inactivation kinetics of Na(+) current. These effects were similar to those induced by alpha-scorpion toxin and sea anemone toxins on Na(+) channels in other cell model. Our data demonstrate for the first time that 4-AP is able to block not only A-type K(+) channels, but also Na(+) channels in rat cerebellar granule cells. It is concluded that the inhibition exerted by 4-AP on Na(+) current likely differs from that provoked by local anesthetics. The possibility that the binding site of neurotoxin receptor 3 may be involved is discussed.

The abnormality of glucose transporter in the erythrocyte membrane of Chinese type 2 diabetic patients

Type 2 diabetes mellitus is characterized by impaired glucose uptake. With a photometric method of recording the erythrocyte suspension absorption during the course of glucose transport across the membranes, we observed that the initial rate of glucose zero-trans entry was decreased significantly in 30 Chinese type 2 diabetic patients as compared to 25 healthy controls. The rate of glucose infinite-cis efflux exhibited no difference between the patients and controls. The measurement of temperature dependence of glucose transport showed that the activation energy for glucose entry was increased in diabetic patients. The inhibitory constant of glucose entry by cytochalasin B (CB) in patients was similar to that of the controls. However, we found that the inhibitory constant was increased significantly in the patient erythrocytes after phloretin treatment. After the erythrocytes were made into stripped white ghosts, the fluorescence quenching experiment was performed. Glucose, CB and phloretin can quench the fluorescence of tryptophan residues in the glucose transporter 1, GLUT1. The abnormality of fluorescence quenching in the erythrocyte membranes of patients was observed. The transfer tendency of tryptophan residues from the hydrophilic environment to the hydrophobic environment was decreased in patient ghosts as binding with glucose, and the opposite tendency appeared as CB and phloretin instead of glucose. We conclude that the decreased in glucose entry in the erythrocyte membranes of diabetic patients was due to the GLUT1 change in structure - mostly the outer domain of the glucose transporter.

Characterization of outward potassium current in embryonic chick heart cells

AIM

To characterize a voltage-dependent outward K+ current in cultured heart cells of 14-16-day-old embryos of yellow chick.

METHODS

The patchclamp technique in the whole-cell configuration was used.

RESULTS

The kinetics and the pharmacology of the outward K+ current in our cell mold were different from those described in white chick. Like the calcium-activated K+ current, blocker of calcium channel, CdCl2, eliminated the current of more than 95%. Isoproterenol provoked an increase of peak amplitude (137% +/- 47%, n = 16 cells) and acceleration of activation kinetics in the outward K+ current (the time reaching a peak current reduced from 36 ms +/- 10 ms to 16 ms +/- 9 ms). This effect of isoproterenol was mimiced by cAMP. In addition, a frequency-dependent decrease in peak amplitude of the current occurred after cAMP-induced phosphorylation.

CONCLUSION

There are species- and/or cell-type-specific difference in the K+ channels properties. In embryonic yellow chick heart cells, the phospholation of channel could not only modulate the activation kinetic properties of the calcium-activated potassium channel, but also change their recovery kinetics.