Synthesis of 2,4-diamino-6-(thioarylmethyl)pyrido[2,3-d]pyrimidines as dihydrofolate reductase inhibitors.

Six 2,4-diaminopyrido[2,3-d]pyrimidines with a 6-methylthio bridge to an aryl group were synthesized and biologically evaluated as inhibitors of Pneumocystis carinii (pc) and Toxoplasma gondii (tg) dihydrofolate reductase (DHFR). The syntheses of analogues 3-8 were achieved by nucleophilic displacement of 2,4-diamino-6-bromomethylpyrido[2,3-d]pyrimidine 14 with various arylthiols. The alpha-naphthyl analogue 4 showed the highest selectivity ratios of 3.6 and 8.7 against pcDHFR and tgDHFR, respectively, versus rat liver (rl) DHFR. The beta-naphthyl analogue 5 exhibited the highest potency within the series with an IC(50) value against pcDHFR and tgDHFR of 0.17 and 0.09 microM, respectively. Analogue 4 was evaluated for in vitro antimycobacterium activity and was shown to inhibit the growth of Mycobacterium tuberculosis H(37)Rv cells by 58% at a concentration of 6.25 microg/mL.

Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase inhibitors and antitumor agents: synthesis and biological activities of 2,4-diamino-5-methyl-6-[(monosubstituted anilino)methyl] pyrido[2,3-d]pyrimidines.

Thirteen 2,4-diamino-5-methyl-6-[(monosubstituted anilino)methyl]pyrido[2,3-d]pyrimidines 5-17 were synthesized as potential Pneumocystis carinii (pc) and Toxoplasma gondii (tg) dihydrofolate reductase (DHFR) inhibitors and as antitumor agents. Compounds 5-17 were designed to investigate the structure-activity relationship of monomethoxy and monohalide substitution in the phenyl ring and N10-methylation of the C9-N10 bridge. The synthetic route to compounds 5-12 involved the reductive amination of a common intermediate, 2,4-diamino-5-methylpyrido[2, 3-d]pyrimidine-6-carbonitrile (18), with the appropriate anilines. N10-Methylation was achieved by reductive methylation. In contrast to previous reports of trimethoprim, the removal of methoxy and chloro groups from the phenyl ring in the 2, 4-diamino-5-methyl-6-[(substituted anilino)methyl]pyrido[2, 3-d]pyrimidine series generally did not decrease DHFR inhibitory activity. The monosubstituted phenyl analogues 5-12 were as potent against pcDHFR and tgDHFR as the previously reported disubstituted phenyl analogues. N10-Methylation generally resulted in a marginal increase in potency against both pcDHFR and tgDHFR. Compounds 5, 7, and 9 were evaluated and shown to inhibit the growth of T. gondii cells in culture at nanomolar concentrations. Compounds 6-8, 9, 11, and 16 were selected by the National Cancer Institute for evaluation in an in vitro preclinical antitumor screening program. All six compounds showed GI50 values in the 10(-7)-10(-9) M range in more than 20 cell lines.

Arterial underfilling does not cause sodium retention in cirrhosis.

PURPOSE: To test the peripheral arterial vasodilation hypothesis of sodium retention in cirrhosis. This states that sodium retention is triggered by arterial underfilling and predicts that development of sodium retention will be associated with significant and related declines in indices of arterial filling that reverse when sodium retention resolves. DESIGN: Longitudinal evaluation of a cohort of patients with alcoholic liver disease. PATIENTS AND METHODS: Eighteen men, 8 of whom were studied twice, 3 three times, 2 four times, and 5 five times (40 between-study comparisons). Between 23 studies, the patients were ascites-free (Group NN). Ascites spontaneously disappeared between seven studies (Group YN), appeared between six studies (Group NY), and remained present between four studies (Group YY). Between-study changes in blood volume, arterial blood pressure, cardiac output, systemic vascular resistance, left atrial volume, left ventricular diastolic diameter, aortic root diameter, aortic blood velocity, plasma norepinephrine and atrial natriuretic factor concentrations, plasma renin activity, and urinary sodium excretion were evaluated by paired t-tests. These changes were also compared among groups by analysis of variance. In addition, correlations among the changes were sought. RESULTS: Systolic, diastolic, and mean arterial pressures, left ventricular diastolic diameter, aortic root diameter, stroke volume, cardiac output, plasma norepinephrine concentration, and systemic vascular resistance were unchanged between studies. Left atrial volume increased between studies in Group NY. Pulse pressure fell more in Group NY than in Groups NN and YN, principally as a result of a decline in systolic blood pressure. Plasma norepinephrine concentration, plasma renin activity, and blood volume rose more in Group NY than in Groups NN, YN, and YY. Changes in both systolic and pulse pressures were directly correlated with the change in sodium excretion but unrelated to the change in plasma norepinephrine concentration. Changes in plasma norepinephrine concentration and plasma renin activity were unrelated to changes in blood pressure, systemic vascular resistance, and urinary sodium excretion. CONCLUSIONS: None of the indices of arterial filling tested except pulse pressure were related to sodium retention. Reduced pulse pressure is inconsistent with arterial underfilling, as peripheral vasodilation instead increases pulse pressure by increasing diastolic run-off. These data do not support the hypothesis that arterial underfilling is the stimulus for sodium retention in alcoholic cirrhosis.

Plasma renin activity in alcoholic liver disease.

PURPOSE AND PATIENTS AND METHODS: The relationship of plasma renin activity (PRA) to indices of circulatory filling and other possible determinants of renin secretion was studied in 31 men with alcoholic liver disease. Characteristics of patients with normal and increased PRA values were examined. Significant differences guided subsequent simple and multiple regression analysis. RESULTS: Supine PRA was increased (greater than 2.4 ng/mL/h on a 200 mEq/d intake of sodium, ranging as high as 33 ng/mL/h) in 14 of 57 studies. Nonascitic patients with elevated PRA values were significantly younger than those with normal PRA values. Among patients without ascites, the plasma atrial natriuretic factor concentration correlated inversely with PRA. Ascitic patients with elevated PRA values had a significantly reduced serum sodium concentration, urinary sodium excretion, creatinine clearance, and arterial pressure. Systemic vascular resistance, plasma norepinephrine and caffeine concentrations, and left atrial volume were similar in patients with and without increased PRA values. Univariate followed by multiple regression analysis identified age and plasma atrial natriuretic factor concentration as significant independent correlates of PRA in patients without ascites (R2 = 0.54). Serum sodium concentration and urinary sodium excretion were significant correlates of PRA in patients with ascites (R2 = 0.80). CONCLUSION: The associates of PRA in alcoholic liver disease are diverse and potentially complex. Age and plasma atrial natriuretic factor concentration are important in patients without ascites. In patients with ascites, tubular delivery of sodium to the macula densa, as modified by the filtered load and proximal reabsorption, appeared to be a principal association of PRA. Indices of circulatory filling did not emerge as clearly independent associations of PRA. Increased PRA values in patients with ascites may be an effect of sodium retention rather than part of its cause.

Arterial vasodilation is not the cause of increased cardiac output in cirrhosis.

A pathological state of arterial vasodilation has been postulated to cause the increased cardiac output commonly observed in cirrhosis. Further, subsequent arterial underfilling has been proposed as the stimulus to sodium retention and ascites formation. Left ventricular size during the cycle of a cardiac contraction is predictably altered by a decrease in afterload. Specifically, increased systolic emptying should be observed. The relationship of left ventricular size during the cardiac cycle to systemic hemodynamic indices and urinary sodium retention was investigated in patients with alcoholic cirrhosis to test these hypotheses. Echocardiographic studies were performed on 24 male patients with alcoholic cirrhosis and compared with the results obtained in 10 age-matched male controls. Patients with cirrhosis had increased cardiac output and heart rate and decreased arterial pressure compared with normal subjects, confirming the presence of a hyperdynamic circulation. Patients with cirrhosis had enlarged left ventricular diameter at both end diastole (0.08 +/- 0.01 vs. 0.07 +/- 0.007 cm/kg dry body wt; P less than 0.001) and end systole (0.06 +/- 0.01 vs. 0.05 +/- 0.005 cm/kg; P less than 0.05). Left ventricular end-diastolic diameter was directly related to blood volume (r = 0.56, P less than 0.005). No significant differences in cardiac output, arterial pressure, or systemic resistance were found between patients with and patients without ascites. Increased cardiac output in cirrhosis occurs in conjunction with an enlarged ventricle throughout the cardiac cycle. The increase in left ventricular end-systolic diameter indicates that diminished afterload is not responsible for the increase in cardiac output. As the diameter of the ventricle during diastolic filling correlates with vascular volume, cardiac output in cirrhosis may be primarily determined by an increase in vascular volume.

Plasma glucagon concentration in cirrhosis is related to liver function but not to portal-systemic shunting, systemic vascular resistance, or urinary sodium excretion.

We tested the hypothesis that increased plasma glucagon concentration resulting from portal-systemic shunting or liver dysfunction causes arterial vasodilation and thereby stimulates sodium retention in cirrhosis. Twenty-seven studies were performed in patients with alcoholic liver disease, 11 of whom had ascites. Liver function was quantitated as the elimination rate of antipyrine, caffeine, and stable isotopes of cholic acid administered both orally (2,2,4,4-2H) and intravenously (24-13C). Portal-systemic shunt fraction was calculated as the ratio of the intravenous and oral clearances of the isotopes of cholic acid. Cardiac output was measured by using Doppler echocardiography. Plasma glucagon concentration was increased in patients with ascites when compared with that in patients without ascites (474 +/- 180 pg/ml vs 245 +/- 120 pg/ml, p = 0.0007) but was unrelated to urinary sodium excretion, heart rate, mean arterial pressure, cardiac output, and systemic vascular resistance (r = -0.48, 0.35, -0.13, 0.18, and 0.22, respectively). Plasma glucagon concentration correlated with the half-lives of all model compounds (r = 0.58, p = 0.002; r = 0.62, p = 0.0008; r = 0.62, p = 0.001; and r = 0.64, p = 0.0005; for caffeine, antipyrine, oral and intravenous cholic acid, respectively) but not with shunt fraction (r = 0.14). Increased plasma glucagon concentration in cirrhosis is probably a result of diminished hepatic clearance. However, increased plasma concentration of glucagon does not appear to cause a hyperdynamic circulatory state or sodium retention.

Atrial volume in cirrhosis: relationship to blood volume and plasma concentration of atrial natriuretic factor.

Increased blood volume, atrial size, and plasma concentration of atrial natriuretic factor are described in cirrhosis. Their interrelationships were examined in 17 men with alcoholic liver disease, 7 with and 10 without ascites. Atrial size was determined by two-dimensional echocardiography. Patients with cirrhosis had significantly increased left atrial volume and plasma concentration of atrial natriuretic factor when compared with normal male subjects. Right atrial volume was normal in patients with cirrhosis, as was left ventricular function. Patients with ascites had significantly increased blood volume and plasma atrial natriuretic factor concentration compared with patients without ascites. Left and right atrial volume did not differ between the groups. Blood volume correlated significantly with left atrial volume, which correlated significantly with plasma concentration of atrial natriuretic factor. Cirrhosis is associated with related increases in vascular volume, left atrial size, and plasma atrial natriuretic factor concentration. Increased blood volume probably contributes to the increase in left atrial volume, which is in turn one reason for the elevation of plasma atrial natriuretic factor concentration.

Atrial natriuretic factor production during upright exercise.

In an attempt to determine factors that are related to atrial natriuretic factor (ANF) release in normal subjects, 10 male volunteers were studied at rest supine, sitting and during treadmill exercise. Echocardiography was used to measure atrial volumes, and a Swan-Ganz catheter was used to measure right atrial pressure and pulmonary artery wedge pressure. Right ventricular ANF increased from 33 +/- 22 pg/ml supine to 72 +/- 32 pg/ml at peak exercise (p less than 0.001). When heart rate, atrial volume and atrial phasic pressure were combined to calculate atrial minute circumferential wall stress, a significant relationship between left and right atrial values for this variable and ANF was present. An association between norepinephrine (NE) and ANF was also present, but in a multivariate analysis it was not significant. This probably does not represent cause and effect but rather an association due to the relationship between NE and heart rate.