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PubMed1992

A comparison of the abilities of nitrobenzylthioinosine, dilazep, and dipyridamole to protect human hematopoietic cells from 7-deazaadenosine (tubercidin).

Nitrobenzylthioinosine, dilazep, and dipyridamole are potent inhibitors of equilibrative transport of nucleosides that may have pharmacological applications in modulating the therapeutic index of nucleoside antimetabolites used in cancer chemotherapy. We have compared the relative abilities of these inhibitors to reduce the toxicity of in vitro exposures to tubercidin against clonogenic progenitor cells of normal human bone marrow (CFU-GEMM, BFU-E, CFU-GM) and of two leukemic human cell lines (HL-60/C1, CCRF-CEM) that differ in their expression of transporter subtypes. Short (1-h) exposures to 1 microM tubercidin alone inhibited colony formation (a) of normal human hematopoietic progenitors (CFU-GEMM, BFU-E, CFU-GM) by 100%, and (b) of HL-60/C1 and CCRF-CEM cells by > 90%. Pretreatment (30 min) with nitrobenzylthioinosine, dilazep, or dipyridamole followed by simultaneous treatment (1 h) with these transport inhibitors during tubercidin exposures reduced toxicity against hematopoietic progenitors and cell lines. Greater reductions of toxicity were consistently seen with bone marrow progenitors and CCRF-CEM cells than with HL-60/C1 cells. For CFU-GEMM, BFU-E, and CFU-GM cells, reductions in tubercidin toxicity of 50-100% were achieved at these concentrations: > or = 0.1 microM (nitrobenzylthioinosine); > or = 0.1 microM (dilazep); and > or = 3.0 microM (dipyridamole). Pretreatment (30 min) followed by simultaneous treatment (1 h) with any of the transport inhibitors (> or = 0.1 microM) and 0.1 microM [3H]-tubercidin blocked the uptake of radioactivity completely in CCRF-CEM cells and only partially in HL-60/C1 cells. These effects, which were consistent with the nucleoside transport phenotypes of CCRF-CEM cells (inhibitor-sensitive) and HL-60/C1 cells (inhibitor-sensitive and inhibitor-resistant), suggested that protection was due to the inhibition of tubercidin uptake via equilibrative nucleoside transport system(s). Light-density mononuclear cells from human bone marrow, of which the clonogenic progenitors represented only a minor (< 0.01%) subpopulation, possessed far fewer nitrobenzylthioinosine-binding sites (2 x 10(4) sites/cell, Kd = 0.7 nM) than either HL-60/C1 cells (1.7 x 10(5) sites/cell, Kd = 0.9 nM) or CCRF-CEM cells (3.3 x 10(5) sites/cell, Kd = 0.5 nM). Initial rates of uptake of 1 microM [3H]adenosine (0-6 s, 20 degrees C) by human bone marrow mononuclear cells were reduced partially by 0.1 microM inhibitor (nitrobenzylthioinosine > dipyridamole > dilazep) and completely by 10 microM inhibitor.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine↗
PubMed1992

Predictive value of dipyridamole thallium imaging in a patient with myocardial bridging but without fixed obstructive coronary artery disease.

Both dipyridamole and exercise-201Tl imaging are sensitive, specific and of prognostic value in patients with suspected coronary artery disease, following myocardial infarction, and undergoing major noncardiac surgery. Though reported sensitivities and specificities vary widely from 60% to 100%, the consensus is that both are between 80% and 90% for both dipyridamole and exercise studies (23). Moreover, when compared directly in the same study populations, the two have equal sensitivities and specificities (9,11,13,23). Transient thallium perfusion abnormalities are the most consistent predictors of adverse cardiac events and have more predictive power than clinical and angiographic parameters. Thallium reversibility may be a better predictor of adverse cardiac events than angiography since it represents more of a physiologic rather than a purely anatomic evaluation of the heart. It is difficult to make an exact comparison of some of the studies in the literature because they use different patient populations, sometimes define coronary stenosis in different ways, may have different cardiac endpoints and may not differentiate between reversible and fixed thallium perfusion defects. Exercise has the advantage of a graded examination and more experience historically and is of importance in a detailed study of cardiopulmonary hemodynamics, as in cardiac transplantation. Dipyridamole is more useful in patients who cannot achieve symptom-limited, submaximal exercise. It may also be more useful for patients who are bedridden or have peripheral vascular disease. Angina occurs less frequently with dipyridamole.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Intravenous dipyridamole technetium-99m MMI myocardial perfusion scintigraphy for detection of coronary artery disease.

To evaluate the efficacy of stress technetium-99m MMI (N-2-methoxy-2-methyl propyl isonitrile) myocardial perfusion scintigraphy (Tc-99m MMI) using intravenous dipyridamole for detection of coronary artery disease (CAD), we collected 66 cases (53 men, 13 women, aged 40-79 years old) between Sept. 1990 and Oct. 1991. The cases were divided into two groups: group I involving 44 patients received coronary arteriography (CAG) examination without previous percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass graft (CABG); group II embracing 22 patients received no CAG examination but all were suffering from old myocardial infarction (MI) evidenced by history and electrocardiography (ECG). All cases underwent Tc-99m MMI planar and single photon emission computed tomography (SPECT) both on intravenous dipyridamole stress and separate day rest tests. Of the 44 group I patients receiving both Tc-99m MMI and CAG, 35 (79.5%) were positive and 7 (16%) were negative by both tests and another 2 (4.5%) were positive by CAG only. Of those positive by both tests, 21 (60%) suffered from identical coronary arterial involvement, including 13 one-vessel disease, 5 double-vessel disease and 3 triple-vessel disease. Of group II patients, 14 suffered from old inferior wall (IW) MI, 6 from old anterior or anteroseptal wall (AW) MI, 1 from old lateral wall (LW) MI and another 1 from combined old anterior and lateral wall (ALW) MI by ECG. Of the 14 patients with IWMI by ECG, all suffered from right coronary artery (RCA) disease but 7 (50%) of them from multivessel disease (MVD) by Tc-99m MMI. 5 of the 6 patients with AWMI by ECG suffered from left anterior descending coronary artery (LAD) disease, but 3 of them from MVD by Tc-99m MMI. Both patients with LWMI and ALWMI by ECG suffered from triple-vessel disease by Tc-99m MMI. The sensitivity of Tc-99m MMI in detecting CAD in group I was 95%, the specificity was 100%. The sensitivity for detection of individual coronary artery disease in LAD, left circumflex coronary artery (LCX) and RCA was 96%, 45% and 89% in this order and the respective specificity was 94%, 100% and 88%. In group II the sensitivity was 95%. The overall sensitivity of intravenous dipyridamole Tc-99m MMI for detection of CAD in groups I and II was 95%; specificity was 100% and accuracy was 95%. In conclusion, stress Tc-99m MMI using intravenous dipyridamole is a valuable method for evaluation and detection of CAD.

Adult↗
PubMed1992

Dipyridamole-thallium scintigraphy predicts perioperative and long-term survival after major vascular surgery.

The purpose of this study was to evaluate the ability of dipyridamole-thallium scintigraphy to predict perioperative and late cardiac events after peripheral vascular operations. A total of 262 patients had dipyridamole-thallium scintigraphy before 87 infrainguinal reconstructions, 108 abdominal aortic aneurysm operations, and 67 aortobifemoral bypass grafts that were placed for occlusive disease. Follow-up extended to 5 years (mean, 31.1 months). Logistic regression analysis selected dipyridamole-thallium scintigraphy redistribution as the best predictor of perioperative events. Fixed defects were not predictive. A Cox proportional hazards model for a variety of clinical risk factors and scan parameters identified fixed defects and a history of congestive heart failure as the strongest predictors of late cardiac events. The presence of greater than 1 or 2 fixed segments were the best predictors in patients with an abnormal scan; redistribution did not predict late events. The risk of combined perioperative or late cardiac events was 29% for infrainguinal, 19% for abdominal aortic aneurysm, and 7.5% for aortobifemoral operations. Life-table analysis showed that after a cluster of perioperative events that occurred primarily in patients with dipyridamole-thallium scintigraphy redistribution, most of the late cardiac morbidity and deaths occurred in patients with fixed defects.

Aged↗
PubMed2005

Gender differences in detecting coronary artery disease with dipyridamole stress myocardial perfusion imaging using 99m-Tc sestamibi gated SPECT.

There are some specifics in the presentation of coronary artery disease (CAD) in women compared with men that may cause diagnostic pitfalls. The accuracy of noninvasive diagnostic testing in women tends to be lower than that in men. Stress myocardial perfusion imaging with 99m-Tc sestamibi gated SPECT is an accurate technique for detecting CAD. Only a few studies have compared dipyridamole stress imaging according to gender. The aim of the study was to compare the diagnostic value of dipyridamole myocardial perfusion imaging with 99m-Tc sestamibi gated SPECT in detecting CAD among patients of both sexes. We studied 62 consecutive patients (38 men, 24 women) using 99m-Tc sestamibi gated SPECT and dipyridamole stress to detect CAD. All the patients also underwent coronary angiography. Overall regional sensitivity was significantly lower in women compared with men (71.4% vs. 92.7%, p=0.039). There were no significant differences for detecting CAD in individual coronary arteries, although regional sensitivity in all three vascular territories was higher in men compared to women. The lowest sensitivity in women was found in the LAD territory (66.6%). Overall regional specificity in men and women was similar and did not reach statistical significance (88.7% vs. 94.7%). Significantly lower specificity in men was found only in the RCA territory (79.1%), compared with that in women (100%). Our results confirmed that there are certain gender differences in the diagnostic performance of dipyridamole stress myocardial perfusion imaging with 99-Tc sestamibi gated SPECT which are assigned to the characteristics of the female population. However, the diagnostic accuracy is also quite high in women, which makes this technique efficient enough in detecting CAD among this population.

Coronary Angiography↗
PubMed2005

[Effect of dipyridamole on the phenomenon of ischemic preconditioning in patients with ischemic heart disease during paired bicycle ergometer tests].

AIM: To assess effect of dipyridamole on ischemic preconditioning (IP) in patients with coronary artery disease by paired bicycle ergometer exercise tests (BETs). MATERIAL AND METHODS: Patients (men, n=12, age 51.7+/-2.5 years) with class II-III stable angina pectoris underwent paired BETs (tests 1 and 2 at 15 min intervals). Test 1 was regarded as baseline and test 2 as the preconditioning one. In 72 hours another pair of BETs was carried out (tests 3 and 4) with same time interval in between. Before second pair of tests the patients received 75 mg of dipyridamole orally. RESULTS: Significant improvements of several parameters of ECG were observed during repeat BETs (increased exercise duration, maximal heart rate and double product, decreased maximal ST-depression and number of ECG leads with >1 mm ST depression). These data suggested the presence of IP phenomenon in both paired BETs. However only test after dipyridamole was associated with significant increase of work load (from 82.4+/-10.5 to 96.4+/-10.1 W, p=0.033), shortening of ST-depression recovery time (from 367+/-45 to 254+30 s, p=0.032) and increase of increment of exercise duration (from 34+/-15 to 81+/-17 s, p=0.034). Number of ECG leads on with segment ST depression >0,1 mv was significantly less during test 4 compared with test 2 (2.6+/-0.4 and 3.4+/-0.5; p=0.045). This data reflected increase of ischemic threshold during test 4. CONCLUSION: Dipyridamole (75 mg orally) augmented IP in patients with coronary artery disease during repeated BETs.

Adult↗
PubMed2006

[Effect of ginkgo biloba extract and dipyridamole on transcription and translation of inducible NO synthbase in rabbits after myocardial ischemia-reperfusion injury].

OBJECTIVE: To investigate the effects of Egb761, an extract of ginkgo biloba , and dipyridamole on inducible NO synthase (iNOS) in rabbits after myocardial ischemia-reperfusion injury. METHODS: After being established into ischemia-reperfusion injury model, 35 rabbits were divided randomly into 5 groups: Group A (the sham group), Group B (the model group), Group C (treated with dipyridamole 0.8 mg/kg), Group D (treated with Egb761, 40 mg/kg), and Group E (treated with Egb761 40 mg/kg combined with dipyridamole 0.8 mg/kg), all the medications were administered by intravenous injection 30 min after reperfusion. After administration, myocardial iNOS mRNA expression was detected by RT-PCR and western blot. RESULTS: Myocardial iNOS mRNA transcriptive expression in the 5 groups were A 0, B 157.11 +/- 17.73, C 202.6 +/- 21.84, D 356.13 +/- 24.18 and E 562.34 +/- 35.19 respectively, showing significant difference between the treated groups and group B (P <0.01). The translative expression of myocardial iNOS in the 5 groups were A 34.24 +/- 15.78, B 75.70 +/- 13.71, C 116.89 +/- 22.57, D 143.75 +/- 16.05 and E 195.09 +/- 22.25 respectively, showing significant difference between the treated groups and group B as well (P < 0.05, P < 0.01). CONCLUSION: Both Egb761 and dipyridamole could increase myocardial iNOS expression in transcriptive and translative levels in rabbits after myocardial ischemia-reperfusion injury, and the combined treatment of them shows a more significant effect.

Animals↗
PubMedDate not supplied

Measurements of the effect of dipyridamole on regional myocardial blood flow with positron emission tomography and the first-pass flow model.

We assessed percent changes of regional myocardial blood flow (RMBF) after infusion of dipyridamole (0.56 mg/kg) with dynamic N-13 ammonia PET and the first-pass flow model. Positron emission tomography (PET) was performed at rest and after infusion of dipyridamole in 17 participants [five normal subjects, five patients with hypertrophic cardiomyopathy (HCM), and seven patients with coronary artery disease]. Dipyridamole increased RMBF 126 +/- 69% (mean +/- SD) in normal subjects and 55 +/- 43% in the patients with HCM. In the cases of coronary artery disease, the percent changes of RMBF were +19 +/- 19% in ischemic areas and +76 +/- 23% in nonischemic areas. These results demonstrate that N-13 ammonia dynamic PET study is useful in assessing the percent changes of RMBF induced by dipyridamole infusion.

Adult↗
PubMed1991

[Effect of ticlopidine and dipyridamole on platelet aggregation and count in patients with chronic stable angina pectoris].

PURPOSE: To compare the ticlopidine and dipyridamole effects on platelets count and aggregation in patients with stable coronary artery disease. PATIENTS AND METHODS: Eighty patients with stable coronary artery disease and mean of 58.3 +/- 5.8 years were studied. They were divided into two equal groups of 40 patients and each one treated with ticlopidine or dipyridamole. Platelets count and aggregation were examined before treatment and at first and fourth weeks of treatment. RESULTS: At the end of fourth week of treatment, spontaneous, induced by ADP or by adrenalin platelet aggregation inhibition was observed, respectively, in 82.5%, 72.5% e 67.5% of the patients in ticlopidine group. The spontaneous, induced by ADP or by adrenalin, platelet aggregation inhibition in the patients of dipyridamole group was, respectively, 40%, 30% e 27.5% (p less than 0.001). The platelets count did not change in both groups. CONCLUSION: The ticlopidine effect is much more evident in platelet aggregation inhibition than dipyridamole, and maybe a choice in the prevention of cardiovascular events.

Coronary Disease↗
PubMedDate not supplied

Dipyridamole potentiates the inhibition of platelet aggregation by aspirin (in human platelet rich plasma and whole blood).

This study investigates the influence of dipyridamole on platelet aggregation as evaluated by a single agonist or a pair of agonists in human platelet rich plasma and whole blood. Dipyridamole up to 30 microM was not found to influence the platelet aggregation of platelet rich plasma or whole blood; aspirin (100 microM), on the contrary, did inhibit platelet aggregation. The inhibition of platelet aggregation by aspirin could be reversed by using high concentrations of agonists or pairs of agonists. In this model dipyridamole inhibited platelet aggregation in both platelet rich plasma and whole blood in a dose-dependent fashion. Thromboxane A2 was less than 10% of controls in aspirin-treated PRP stimulated with low or high concentrations of collagen or with a pair of agonists. This study suggests that dipyridamole has direct antiplatelet activity in platelet rich plasma and whole blood when the cyclooxygenase pathway is blocked by aspirin.

Adult↗
PubMed1991

Tomographic myocardial perfusion imaging with technetium-99m-teboroxime at rest and after dipyridamole.

This study was done to determine whether the rapidly clearing myocardial perfusion agent 99mTc-teboroxime (SQ 30217, Cardiotec) could be combined with tomographic imaging to accurately quantify regional myocardial blood flow distribution in anesthetized dogs. Following stenosis of the anterior descending (LAD, n = 10) or circumflex (LCX, n = 5) coronary arteries, teboroxime was administered simultaneously with radioactive microspheres, at rest and following infusion of dipyridamole (0.15 mg/kg/min x 4 min). Tomographic imaging began 1 min after each teboroxime injection and continued for 12 min. For LAD stenosis, when the dipyridamole study was performed first, teboroxime activity in the center of the ischemic region was closely correlated with tissue microsphere content. However, the severity of the dipyridamole-induced flow deficit was underestimated by teboroxime when the rest study was performed first. Our results show that despite rapid myocardial clearance, tomographic imaging of 99mTc-teboroxime provides reasonably accurate quantitation of dipyridamole-induced anterior wall perfusion defects, but that the flow deficit is underestimated when a rest study is performed first or when the defect is located in the inferior wall.

Animals↗
PubMed1991

Dipyridamole-thallium imaging: minimum dose requirements.

A total of 372 consecutive dipyridamole-thallium studies were reviewed to determine if a relationship existed between the dose of dipyridamole administered and the likelihood that thallium images would show reversible defects. Men who received a dose of less than 31 mg were less likely to have thallium redistribution (P = 0.0001). Until the ideal study involving repeat testing with incremental dipyridamole doses on different days is carried out, the authors recommend that a minimal dose of 31 mg be administered for dipyridamole-thallium imaging.

Coronary Vessels↗
PubMed1991

Role of dipyridamole-echocardiography test in the evaluation of coronary reserve after coronary artery bypass grafting.

The object of this study was to assess the usefulness of the dipyridamole-echocardiography test in the early evaluation of coronary artery bypass grafting, when the use of an exercise stress test is precluded. We studied 39 consecutive patients (37 men and two women, mean age 57.3 years) referred to our institute for elective coronary artery bypass. Five patients had single, 12 patients double, 20 patients triple vessel disease, and two had left main stem disease. Nineteen left internal mammary artery grafts, 20 sequential grafts, and 39 single vein grafts were performed. All the patients were subjected to the test before (time range 1 to 3 days) and after (time range 6 to 10 days) the operation in the absence of therapy. Dipyridamole was administered intravenously 0.56 mg/kg over 4 minutes (low dose); if no effect was apparent, an additional 0.28 mg/kg over 2 minutes (high dose) was given. During the test, blood pressure and a twelve-lead electrocardiogram were monitored. An arbitrary wall motion score was derived by dividing the left ventricle into six regions and grading from 0 to 3-normokinetic, hypokinetic, akinetic, and dyskinetic zones. Preoperatively the test was positive in 38 patients as evidenced by wall motion abnormalities (36 patients had electrocardiographic changes) and in one patient by electrocardiographic changes and chest pain; 22 tests were positive after the low dose and 17 after the high dose. Angina was present in 33 patients. Mean wall motion score was 1.64 per patient in the basal condition and 4.03 per patient after the test (p less than 0.001). After coronary bypass in three patients the test was positive at the same dosage that was used preoperatively, as shown by wall motion abnormalities (in two patients by electrocardiographic changes, as well). Four patients had symptoms. Furthermore, at 6 months' follow-up, a treadmill stress test performed in these three patients was positive for ischemia and angina. The wall motion score was 1.25 per patient in the basal condition and 1.53 per patient after the test (no significant difference). When the preoperative wall motion score obtained after dipyridamole echocardiography was compared with the postoperative score, a statistically significant difference was seen: 4.03 per patient versus 1.53 per patient (p less than 001). In eight patients we observed an improvement of basal myocardial contractility after the operation, which indicates the reversibility of wall motion abnormalities observed before coronary bypass. In conclusion our data show that the dipyridamole-echocardiography test is a suitable method for the early assessment of bypass grafting when other methods, exercise dependent, are not indicated.(ABSTRACT TRUNCATED AT 400 WORDS)

Angina Pectoris↗
PubMed1990

[Risk stratification after uncomplicated myocardial infarct: the usefulness of the echocardiographic-dipyridamole test].

To assess the value and safety of echo-dipyridamole test in risk stratification soon after an uncomplicated acute myocardial infarction, 56 consecutive patients were enrolled in a prospective study with a 1-year follow-up period for new coronary events. Echo-dipyridamole and symptom-limited ECG stress test were performed respectively 14 to 20 days and 4 to 5 weeks after acute event. Echo-dipyridamole test was performed administering 0.84 mg/kg iv of the drug in 10 min: any worsening of left ventricular regional wall motion was considered as a positive test. Up to December 1989, 43 out of 56 patients had their follow-up period completed: the infarction was anterior in 13 (30%), inferior in 22 (51%), non-Q wave in 8 (19%); mean age was 55 +/- 10; basal echocardiographic ejection fraction was 52 +/- 6%. There were no major complications during echo-dipyridamole test. Coronary events occurred in 7 patients (16%): reinfarction in 3, angina in 4; there were no cardiac deaths. A positive echo-dypiridamole test was observed in 12/43 patients (28%); sensitivity versus coronary events was 43%, specificity 75%, negative predictive value 87%. Ten out of 43 patients (23%) had positive and 9/43 (21%) non valuable ECG stress test: sensitivity versus coronary events was 50%, specificity 75%, predictive negative value 88%. The 2 tests showed no significant difference in detecting patients at risk of future coronary events.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Dipyridamole-exercise association in the diagnosis of ischemic heart disease.

Dipyridamole-exercise ECG test (DET) was found to present a greater sensitivity than exercise or dipyridamole ECG test alone in detecting ischemic heart disease (IHD). A group of 39 patients with probable IHD and negative exercise test was investigated by i.v. dipyridamole administration. Eight subjects presented significant ECG changes. The remaining 31 subjects were submitted to a new exercise test which became positive in 7 subjects (23%). The percentage increases to 38% by taking into account the positive dipyridamole test. The authors concluded that DET substantially improve the diagnosis of myocardial ischemia in subjects with probable IHD and negative exercise test.

Coronary Disease↗
PubMed1990

[Blood levels of opioid peptides and alpha interferon under the action of dipyridamole].

The levels of met-enkephalin (ME), beta-endorphin (BE), and alpha-interferon (a-IFN) have been determined in the human blood 1 day after dipyridamole administration. Dipyridamole led to an increase in serum a-IFN concentration up to 3 times, and to simultaneous rise of the lymphocytes ability to produce a-IFN. The content of BE did not depend on dipyridamole treatment, but ME level achieved 110 +/- 4.8 pg/ml (compare to 79.5 +/- 7.6 pg/ml in control). Positive interrelation has been found out between individual ME concentrations and lymphocyte abilities to a-IFN production with the coefficient of correlation equal to 0.69. The effect of dipyridamole on ME level is suggested to develop via a-IFN interaction with the opioid systems.

Adult↗
PubMed1989

[Experience with the dipyridamole test in the diagnosis of coronary insufficiency].

In 1980-86 263 dipyridamole tests were made before or after ergometry on account of the diagnosis of coronary insufficiency and possible indication for coronarography. The sensitivity and specificity was evaluated in a group of 101 subjects where both examinations had been made. As a reference method the authors used ergometry with more strict criteria of positivity of the two tests (deviations of segment ST 0.2 mV, incl. stenocardia) which are in good agreement with coronarography. The sensitivity was 58.2 and the specificity 96% (in men 61.4 and 100%). On combination of 98 dipyridamole tests with immediately following ergometry of 39 negative ergometries 23 (58.6%) changed to positive. Of 38 coronarographies the dipyridamole test was positive in 73% and in some patients with affections of the three main branches it was negative. There was also one serious complication: a new myocardial infarction. Because of lower sensitivity the dipyridamole test does not replace ergometry, except when the latter cannot be performed. The combination of the two tests sensitizes ergometry. On account of the high specificity ergometry can be omitted when the test is positive, in particular in men. For diagnostic purposes the stricter variant of criteria for evaluation of the test is more reliable and almost specific.

Adult↗
PubMedDate not supplied

[The role of adenine nucleotide catabolism in the interphase death of thymocytes, caused by papaverine and dipyridamole].

Papaverine and dipyridamole induce the interphase death of thymocytes rapidly growing four hours later and reaching its maximum by the seventh-eighth hour of the cell incubation. To induce death of thymocytes no constant presence of these preparations in the incubation medium is needed, a definite (for each of preparations) time of the contact with cells being enough. The interphase death of thymocytes induced by papaverine and dipyridamole is preceded by acceleration of the release of adenine nucleotide catabolism products from cells mainly as hypoxanthine and inosine, respectively. These both processes are induced by papaverine for a shorter period of its incubation with cells than by dipyridamole and the joined use of these substances intensifies the above processes. The analysis of the data obtained indicates that thymocytes under the effect of papaverine die rather from the exhaustion of the adenine nucleotide pool, than from a decrease in the adenylate charge of cells. Exogenous adenosine essentially removes the toxic effect of papaverine but not of dipyridamole. Addition of adenine and inosine to thymocytes does not affect their survival rate in the presence of the preparations under study.

Adenine Nucleotides↗