OBJECTIVE: To investigate the protective effect of combined administration of verapamil and nitroglycerin on the function of canine transplanted lungs. METHODS: Twenty orthotopic left lung transplantations were performed in 40 canines, which were randomly divided into 4 groups. In group I (control), the donor lungs were perfused and preserved with LPD solution, while group II with LPD solution plus verapamil 0.1 g/L, group III with LPD solution plus nitroglycerin 0.1g/L, and group IV with LPD solution plus verapamil 0.1 g/L and nitroglycerin 0.1 g/L. Hemodynamics and graft gas exchange were assessed 0, 2 and 4 h after the operation. The lung grafts were harvested to measure the wet/dry weight ratio, malondialdehyde (MDA) contents and superoxide dismutase (SOD) activity. RESULTS: Compared with group I, II and III, the mean pulmonary artery pressure (MPAP), pulmonary vascular resistance index (PVRI), partial pressure of oxygen in arterial blood (PaO₂), dynamic compliance (Cdyn) and alveolar-arterial oxygen tension volume [P(A- a)O₂] in group IV were improved significantly (P<0.05). No significant difference in the partial pressure of carbondioxide (PaCO₂) and peak inspiratory pressure (PIP) was observed in the 4 groups (P>0.05). In group IV, the wet/dry weight ratio and MDA contents were lower than those in the other 3 groups, and the SOD activity was significantly higher than that of the other 3 groups (P<0.05). CONCLUSION Verapamil and nitroglycerin in LPD solution can protect the respiratory function of canine lung grafts by attenuating pulmonary edema and oxidative stress.
Animals ; Blood Gas Analysis ; Dogs ; Hemodynamics ; Lung ; Lung Transplantation ; Nitroglycerin ; pharmacology ; Organ Preservation ; Protective Agents ; Reperfusion Injury ; Verapamil ; pharmacology

Cardiac dysfunctions such as myocardial functional failure and ventricular arrhythmia have been largely attributed to intracellular Ca2+ overload. One of the mechanisms of intracellular Ca2+ overload involves a rapid influx of Ca2+ via Na(+)-Ca2+ exchange during the reperfusion which utilizes the accumulation of Na+ in myocytes during ischemic cardiac arrest. Possible sources of the intracellular Na+ accumulation include Na+ channel, Na(+)-H+ exchange, Na(+)-Ca2+ exchange, and Na+ background current. In this study, we studied the role of the Na+ background current in intracellular Na+ accumulation during the cardiac arrest by measuring the Na+ background current in guinea pig ventricular myocytes with whole cell clamp method and evaluating the effects of cardioprotective drugs on the Na+ background current. The results were as follows: (1) The Na+ background inward current at -40 mV membrane potential was larger at Ca2+ free solution than 1.8 mM Ca2+ solution. (2) The Na+ background current was not affected by verapamil. (3) 2 microM O-(N, N-hexamethylene)-amiloride (HMA) decreased the Na+ background current at negative membrane potential. (4) The new cardioprotective drug, R 56865, decreased the Na+ background current. These results suggest that the Na+ background current plays a role in increasing the intracellular Na+ activity during high K+ cardioplegia and the blocking effect of myoprotective drugs, such as R 56865, on the Na+ background current may contribute to myocardial protection after cardioplegia.
Amiloride/pharmacology ; Animal ; Guinea Pigs ; Heart/*drug effects ; Heart Arrest, Induced ; Myocardium/metabolism ; Piperidines/pharmacology ; Potassium/pharmacology ; Sodium/*metabolism ; Support, Non-U.S. Gov't ; Thiazoles/pharmacology ; Verapamil/pharmacology

We studied medium alkalinization in Salvia miltiorrhiza suspension cultures treated with salicylic acid and the effect of Ca2+ in this process through application of calcium channel antagonists (Verapamil, LaCl3, LiCl, 2-APB) and ionophore A23187. The results show that salicylic acid could induce significant medium alkalinization in S. miltiorrhiza culture. Verapamil and LaCl3 or LiCl and 2-APB, two different groups of calcium channel antagonist, significantly inhibited the medium alkalinization induced by salicylic acid. However, the suppression effect of verapamil or LaCl3 on medium alkalinization induced by salicylic acid was higher than that of LiCl or 2-APB. When two types of calcium channel inhibitor (LaCl3 and 2-APB) were used together, the medium alkalinization induced by salicylic acid was completely suppressed and even reduced the pH in medium. On the other hand, A23187 could promote the medium alkalinization. Based on the results above, we speculated that salicylic acid could induce significant medium alkalinization in S. miltiorrhiza culture, depending on the calcium from both extracell and intracell. Moreover, calcium from extracell plays a more dominant role in this process. Reveal of relationship in this research between Ca2+ and medium alkalinization can provide theory evidence for mechanism of the plant secondary metabolism.
Calcimycin ; pharmacology ; Calcium ; chemistry ; Calcium Channel Blockers ; pharmacology ; Calcium Ionophores ; pharmacology ; Cell Culture Techniques ; Culture Media ; chemistry ; Salicylic Acid ; pharmacology ; Salvia miltiorrhiza ; metabolism ; Verapamil ; pharmacology

In order to study the roles of HBx and calcium inhibitor verapamil in apoptosis of human normal hepatic cells, L02-off, a pTet-off stably integrated human hepatic cell line was established, in which HBx expression was tightly induced by Doxycycline. The effect of different amounts of HBx and verapamil on apoptosis of human normal hepatic cells was detected. The study showed that apoptosis was triggered by accumulation of intracellular HBx, while verapamil had no effects on the apoptotic process. It was concluded that apoptosis mediated by HBx was dose-dependent but calcium-independent.
Apoptosis ; drug effects ; Calcium ; pharmacology ; Calcium Channel Blockers ; pharmacology ; Cells, Cultured ; Dose-Response Relationship, Drug ; Hepatitis B Antigens ; pharmacology ; Hepatocytes ; cytology ; Humans ; Trans-Activators ; pharmacology ; Verapamil ; pharmacology

In order to study the roles of HBx and calcium inhibitor verapamil in apoptosis of human normal hepatic cells, L02-off, a pTet-off stably integrated human hepatic cell line was established, in which HBx expression was tightly induced by Doxycycline. The effect of different amounts of HBx and verapamil on apoptosis of human normal hepatic cells was detected. The study showed that apoptosis was triggered by accumulation of intracellular HBx, while verapamil had no effects on the apoptotic process. It was concluded that apoptosis mediated by HBx was dose-dependent but calcium-independent.
Apoptosis/*drug effects ; Calcium/pharmacology ; Calcium Channel Blockers/pharmacology ; Cells, Cultured ; Dose-Response Relationship, Drug ; Hepatitis B Antigens/pharmacology ; Hepatocytes/*cytology ; Trans-Activators/*pharmacology ; Verapamil/*pharmacology

The intensive use of chemotherapeutic agents for the treatment of cancer has resulted in the cure or improved survival of many patients. But unfortunately, many cancers including human hepatocellular carcinoma (HCC) don't respond to chemotherapy. One of the major mechanisms for the drug resistance in the HCC is an elevated MDR1 RNA expression which makes cells become multidrug resistant. To overcome the multidrug resistance (MDR) phenotype, a high dose of verapamil is required both clinically and experimentally. Accordingly we have examined the MDR modulating effects with combinations of tamoxifen, cyclosporin A, and verapamil in vitro with the physiologically achievable concentrations of each agent, i.e., 2.0 microM/L for tamoxifen, 1.6 microM/L for cyclosporin A, and 2.5 microM/L for verapamil respectively in HCC lines. As expected, verapamil alone with the physiologically achievable concentration at which we tested didn't enhance the doxorubicin cytotoxicity in the HCC lines. Furthermore, any verapamil combination with cyclosporin A or tamoxifen was not effective in overcoming the doxorubicin resistance in the high MDR1 expressor (Hep-G2) line. However tamoxifen reduced the IC50 of doxorubicin by a factor of 1.9 in the low MDR1 expressor (SK-Hep1) and 1.1 in the high MDR1 expressor line (p< 10(-5) respectively). Of interest, combinations of tamoxifen and cyclosporin A showed a significant reduction in the IC50 of doxorubicin in both HCC lines. The IC50 of doxorubicin was reduced by a factor of 3.9 and 1.3, i.e., from 0.023943 micrograms/ml to 0.006157 micrograms/ml (p< 10(-5)) in the SK-Hep1 cell line, and 0.068819 micrograms/ml to 0.052442 micrograms/ml (p< 10(-5)) in Hep-G2 respectively when tamoxifen and cyclosporin A were administered together. Both the estrogen and progesterone receptors in the SK-Hep1 and Hep-G2 lines were less than 0.01 fmol/mg of cytosol protein, respectively. It is therefore suggested that the reversal of doxorubicin resistance is unrelated to their anti-estrogenic activity in the HCC lines. Three modulator combinations of tamoxifen, cyclosporin A, and verapamil were not more effective than the combination of tamoxifen and cyclosporin A on the sensitivity to doxorubicin. MDR modulators of tamoxifen, cyclosporin A, and verapamil didn't reduce the IC50 of cisplatin to the clinically achievable concentration range in HCC lines. In summary, the combination of tamoxifen and cyclosporin A at the concentrations normally seen after clinical administration of these modulators showed significant synergism on the sensitivity to doxorubicin in both low and high MDR1 expressor HCC lines. These data indicate the need for in vivo trials.
Antineoplastic Agents/*pharmacology ; Carcinoma, Hepatocellular/*physiopathology ; Cyclosporine/*pharmacology ; Drug Resistance ; Human ; Liver Neoplasms/*physiopathology ; Support, Non-U.S. Gov't ; Tamoxifen/*pharmacology ; Tumor Cells, Cultured/drug effects ; Verapamil/*pharmacology

Platelet aggregability was compared between platelets isolated from normal subjects and patients with diabetes mellitus in order to evaluate the effects of calcium channel blockers and insulin on the platelet function. The threshold aggregating concentration of adenosine diphosphate (ADP), which induces the second phase aggregation and reflects the platelet release reaction, was found to be significantly lower in diabetics than in normal subjects (1.8 microM vs 7.5 microM ). It was observed that the second phase aggregation curve induced by ADP was inhibited by in vitro treatment of platelets with insulin (10-100 microU/ml), verapamil (1-10 microM ), and diltiazem (1 microM) in diabetics. The result also shows that the inhibition was enhanced when insulin and calcium channel blockers were used together for in vitro treatment of diabetic platelets. Thus, the present study suggests that the use of calcium channel blockers combined with insulin would be more effective than the use of insulin alone in the prevention of diabetic vascular disease.
Calcium Channel Blockers/pharmacology* ; Comparative Study ; Diabetes Mellitus/blood* ; Diabetes Mellitus/drug therapy ; Diltiazem/pharmacology ; Human ; Insulin/pharmacology* ; Platelet Aggregation/drug effects* ; Verapamil/pharmacology

The chemosensitizing effects of cyclosporin A and verapamil on the cytotoxicity of adriamycin were investigated using MTT assay against two human retinoblastoma cell lines, Y79 and WERI-Rb-1. Y79 and WERI-Rb-1 were totally resistant to doses up to 5.0 micrograms/ml of verapamil. Cyclosporin A inhibited the survival of Y79 and WERI-Rb-1 dose-dependently, however, the maximum inhibition at the highest concentration tested (5.0 micrograms/ml) was less than 50% (% survival at 5.0 micrograms/ml of cyclosporin A: 65.6% and 66.9% in Y79 and WERI-Rb-1, respectively). Combination of cyclosporin A and verapamil did not further inhibit the survival of Y79 and WERI-Rb-1 compared with cyclosporin A alone. Adramycin inhibited the survival of Y79 and WERI-Rb-1 dose-dependently. The chemosensitizing effects of cyclosporin A and verapamil on the cytotoxicity of adriamycin were evaluated in terms of sensitizing index (SI: the ratio of IC50 to adriamycin alone to IC50 to adriamycin in the presence of cyclosporin A and/or verapamil). Cyclosporin A significantly enhanced SI and the addition of verapamil enhanced SI further: SI values at 5.0 micrograms/ml of cyclosporin A, 5.0 micrograms/ml of cyclosporin A plus 1.5 micrograms/ml of cyclosporin A plus 1.5 micrograms/ml of verapamil, 5.0 micrograms/ml of cyclosporin A plus 3.0 micrograms/ml of verapamil were 2.0, 2.6 and 2.8 in Y79 and 2.6, 5.8 and 9.7 in WERI-Rb-1, respectively. These results suggest that cyclosporin A and verapamil are promising chemosensitizers to adriamycin in the treatment of retinoblastoma.
Cell Survival/drug effects ; Cyclosporine/*pharmacology ; Doxorubicin/*pharmacology ; Eye Neoplasms/drug therapy/*pathology ; Humans ; Retinoblastoma/drug therapy/*pathology ; Tumor Cells, Cultured ; Verapamil/*pharmacology

The purpose of this study was to clarify the characteristics of the pacemaker cells in the left ventricular outflow tract (aortic vestibule) and compare them with those of the cells in the sinoatrial node (SAN). By using conventional intracellular microelectrode technique to record their action potentials, some ionic channel blockers were used to observe their electrophysiological effects on the two types of pacemaker cells in the rabbit, especially on the ionic movement during phase 0 and phase 4. The results obtained are as follows. (1) Perfusion with 1 micromol/L verapamil (VER) resulted in a significant reduction in the amplitude of action potential (APA), maximal rate of depolarization (V(max)), absolute value of the maximal diastolic potential (MDP), velocity of diastolic depolarization (VDD) and rate of pacemaker firing (RPF), and also a prolongation of the 90% of the duration of action potential (APD(90)) in the pacemaker cells of the SAN and aortic vestibule (P<0.05). (2) Perfusion with 180 micromol/L nickel chloride (NiCl2) resulted in a decrease in VDD in the two types of the pacemaker cells (P<0.01). APA, V(max) and RPF fell notably, and the APD(90) prolonged in the sinoatrial node cells (P<0.05). (3) 2 mmol/L 4-aminopyridine (4-AP) led to a increase in VDD in both types of pacemaker cells (P<0.01). At the same time the absolute values of MDP, APA and V(max) decreased significantly, and APD(90) prolonged notably (P<0.05). During the perfusion, RPF in SAN increased markedly, while RPF in aortic vestibule exhibited no significant change. (4) 2 mmol/L cesium chloride (CsCl) led to a decrease in VDD and RPF in the two types of the pacemaker cells (P<0.05).These results suggested: (1) the ion currents in phase 0 and phase 4 of depolarization and repolarization of slow-response activity in aortic vestibule are similar to those in dominant pacemaker cells of sinoatrial node; (2) for the pacemaker cells in the left ventricular outflow tract, Ca(2+) current is the main depolarizing ion current of the phase 0, K(+) current is the main factor responsible for the repolarization. Attenuation of K(+) current is responsible for the phase 4 spontaneous depolarization. In addition, it seems that I(Ca-T), I(Ca-L) and I(f ) play some role in the pacemaker currents.
4-Aminopyridine ; pharmacology ; Action Potentials ; drug effects ; Animals ; Aorta, Thoracic ; cytology ; physiology ; Female ; Male ; Nickel ; pharmacology ; Periodicity ; Rabbits ; Sinoatrial Node ; cytology ; physiology ; Verapamil ; pharmacology

In this paper, membrane current properties of the fully-grown oocytes from toad, Bufo bufo gargarizans, were studied by using two-microelectrode voltage clamp technique. Axion of adult female toad was destroyed, and then ovarian lobes containing oocytes in stage I to VI were removed and incubated in Ca(2+)-free ND96 solution with collagenase (1.5 mg/ml) for 1 h. Subsequently, the oocytes were washed in Ca(2+)-free ND96 solution for 10 min to completely remove the follicular layer. For the experiments only the oocytes in stage V and VI were selected and used during 1 to 5 d. The membrane was depolarized from a holding potential of -80 mV to +60 mV in 10 mV step. It was found that a sustained outward current was elicited by depolarization. Potassium channel blockers (tetraethylammonium chloride, TEA, 10 mmol/L and 4-aminopyridine, 4-AP, 10 mmol/L) reduced the outward current to (23.4+/-0.72)% of the maximum. However, further addition of chloride channel blocker (5-nitro-2, 3-phenypropylamino benzoate, NPPB, 30 micromol/L) could almost completely block the outward current to (2.1+/-0.08)% of the maximum. In the presence of TEA and 4-AP, removal of extracellular Ca(2+) or adding verapamil (40 micromol/L), could also reduce the outward current to (2.2+/-0.04) % and (3.1+/-0.15) % of the maximum, respectively. It is concluded that calcium-dependent chloride channels exist in plasma membrane of Bufo bufo gargarizans oocytes, besides potassium channels.
4-Aminopyridine ; toxicity ; Animals ; Bufo bufo ; Calcium ; metabolism ; Cell Membrane ; metabolism ; Chloride Channels ; drug effects ; physiology ; Female ; Nitrobenzoates ; pharmacology ; Oocytes ; metabolism ; Tetraethylammonium Compounds ; pharmacology ; Verapamil ; pharmacology