Angiotensin II subtype AT1 receptor blockade prevents hypertension and renal insufficiency induced by chronic NO-synthase inhibition in rats.

Aim of the present study was to investigate the influence of the angiotensin II (ANG II) subtype 1 (AT(1)) receptor blockers fonsartan and losartan on blood pressure, cardiac -dynamics and -metabolism as well as functional and morphological changes in the kidney of rats after long-term inhibition of the nitric oxide (NO) synthase by N(G)-nitro-L-arginine methyl ester (L-NAME). Oral chronic treatment with L-NAME in a dose of 25 mg/kg/d over 6 weeks caused a significant increase in systolic blood pressure (198+/-13 mmHg) when compared to untreated rats (144+/-4 mmHg). Animals receiving simultaneously L-NAME and fonsartan (10 mg/kg/d) or losartan (30 mg/kg/d) were protected against blood pressure increase. L-NAME treatment caused a significant decrease in glomerular filtration rate (GFR) from 4.52+/-0.81 to 1.34+/-0.26 ml/kg(-1)/min(-1) and renal plasma flow (RPF) from 10.52+/-1.29 ml/kg(-1)/min(-1) to 5.66+/-1.06 ml/kg(-1)/min(-1). Co-treatment with fonsartan and losartan prevented L-NAME-induced reduction in GFR and RPF. There was no difference in urine, sodium and potassium excretion in groups under investigation. Plasma renin activity (PRA) was further stimulated by fonsartan and losartan treatment. L-NAME produced a significant elevation in urinary protein excretion which was antagonised by both AT(1) blockers. Isolated hearts from animals treated with L-NAME showed a significant prolongation in the duration of ventricular fibrillation and a significant decrease in coronary flow as compared to control hearts. Treatment with fonsartan and losartan significantly decreased the duration of ventricular fibrillation as compared to L-NAME group. In addition, both AT(1) blockers given alone significantly reduced the duration of ventricular fibrillation as compared to hearts from untreated controls. During ischemia the cytosolic enzymes lactate dehydrogenase and creatine kinase as well as lactate in the coronary effluent were significantly increased in the L-NAME group. Myocardial tissue values of glycogen, ATP, and creatine phosphate were decreased, whereas lactate was increased. Fonsartan and losartan treatment totally abolished these effects. Histological examination of kidneys revealed that simultaneous administration of fonsartan and losartan with L-NAME abolished L-NAME-induced arteriolar hyalinosis, segmental sclerosis of glomerular capillaries and focal tubular atrophies. In conclusion, long-term blockade of ANG II subtype AT(1) receptors by fonsartan and losartan prevented L-NAME-induced hypertension, renal insufficiency, as well as cardio-dynamic, cardio-metabolic, and morphological deteriorations.

Ramipril prevents the detrimental sequels of chronic NO synthase inhibition in rats: hypertension, cardiac hypertrophy and renal insufficiency.

Inhibition of the angiotensin converting enzyme (ACE) with ramipril was studied in male Wistar rats during long-term inhibition of nitric oxide (NO) synthase by NG-nitro-L-arginine methyl ester (L-NAME). Chronic treatment with L-NAME in a dose of 25 mg/kg per day over 6 weeks caused myocardial hypertrophy and a significant increase in systolic blood pressure (245 +/- 16 mmHg) as compared to controls (155 +/- 4 mmHg). Animals receiving simultaneously L-NAME and ramipril were protected against blood pressure increase and partially against myocardial hypertrophy. L-NAME caused a significant reduction in glomerular filtration rate (GFR: 2.56 +/- 0.73 ml.kg-1.min-1) and renal plasma flow (RPF: 6.93 +/- 1.70 ml.kg-1.min-1) as compared to control (GFR: 7.29 +/- 0.69, RPF: 21.36 +/- 2.33 ml.kg-1.min-1). Addition of ramipril prevented L-NAME-induced reduction in GFR and renal plasma flow. L-NAME produced an elevation in urinary protein excretion and serum creatinine and a decrease in potassium excretion which was antagonised by ramipril. L-NAME-induced increase in plasma renin activity (PRA) was further elevated with ramipril treatment. Isolated hearts from rats treated with L-NAME showed increased post-ischaemic reperfusion injuries. Compared to controls duration of ventricular fibrillation was increased and coronary flow reduced. During ischemia the cytosolic enzymes lactate dehydrogenase and creatine kinase, as well as lactate in the venous effluent were increased. Myocardial tissue values of glycogen, ATP, and creatine phosphate were decreased, whereas lactate was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Sorbitol-accumulating pyrimidine derivatives.

The novel compounds SDI 157 (2-methyl-4(4-N,N-dimethylaminosulfonyl-1-piperazino)pyrimid ine, CAS 131816-54-1) and SDI 158 (2-hydroxymethyl-4-(4-N,N-dimethylaminosulfonyl-1- piperazino) pyrimidine, CAS 140687-51-0) have been found to be inhibitors of sorbitol dehydrogenase. In normal and diabetic animals both compounds induced a dose-dependent increase of tissue sorbitol, especially in the peripheral nerve, without alteration of the blood glucose. In contrast to SDI 158, SDI 157 does not act in vitro. However, in the isolated perfused rat liver SDI 157 induced a high sorbitol release and plasma samples of animals treated with SDI 157 induced a sorbitol accumulation in vitro in erythrocytes like SDI 158. SDI 157 seems to be a prodrug. In accordance with the polyol theory, the chronic administration of SDI 157 to diabetic rats accelerated the cataract development and depleted the lens of total and oxidized glutathione. Surprisingly, however, it accelerated the motor nerve conduction velocity in normal and diabetic rats, normalized the glomerular filtration rate in diabetic rats and did not induce retinal capillary lesions in normal rats or aggravate those in diabetic rats. At single oral doses up to 100 mg/kg, SDI 157, was well tolerated by diabetic and normal rats. Except for a reduction of drinking water consumption, the chronic administration of SDI 157 in drinking water at doses up to 100 mg/kg per day had no side effects in normal, diabetic and galactoselfructose-rich diet rats.

Interference in clinical laboratory tests, with special regard to the bilirubin assay: effects of a metabolite of the new prolyl 4-hydroxylase inhibitor, Lufironil.

During the toxicological examination of the fibrosuppressive agent, Lufironil (INN), in rats a dose-dependent positive reaction for urinary bilirubin was observed. This positive reaction was found in quantitative assays, and when using test strips. The positive reaction for bilirubin in these assay systems was caused by a metabolite of Lufironil. It was not due to drug toxicity, and it was not caused by any endogenous substrate produced under the influence of Lufironil. The compound responsible for this reaction was isolated by HPLC and its structure determined by spectroscopic methods. The structure was confirmed by synthesis, starting from pyridine-2,4-dicarboxylate. The synthesized compound and the compound in urine gave an identical reaction with the test reagent for bilirubin.

Recombinant hirudin, a new anticoagulant, has no effect on faecal blood loss.

Hirudin is a selective thrombin inhibitor with strong anticoagulant properties which could elicit gastro-intestinal bleeding. A double-blind cross-over study of the effects of hirudin on gastro-intestinal bleeding was therefore conducted on 12 healthy, consenting males. After labelling erythrocytes with 51Cr and returning them intravenously, stools were collected for 2 days to measure radioactivity and hence baseline faecal blood loss. After injection of hirudin or placebo stools were collected for 3 days. Partial thromboplastin time was measured sequentially after medication with hirudin or placebo. This procedure was repeated after injection of the alternate medication 1 week later. Hirudin was tolerated well. Mean faecal blood loss associated with hirudin was slightly higher than with placebo (1.63 ml vs 1.15 ml over 3 days; 95% confidence interval for the difference between hirudin and placebo was -0.68 to 1.63) but these differences are clinically irrelevant. After hirudin injection PTT was elevated to about twice the baseline values but returned to baseline within 12 h after the last hirudin injection.

Determination of r DNA hirudin and A-human thrombin- hirudin complex in plasma samples: enzyme linked immunosorbent assays for hirudin and complex vs. chromogenic thrombin substrate assay.

rDNA hirudin plasma concentrations in man and rhesus monkeys were determined over a period of 15 and 24 h. The plasma concentration of alpha-human thrombin-hirudin complex was measured after administration of the complex to rhesus monkeys. The complex was also determined after administration of hirudin to man and rhesus monkeys to study a possible formation of a complex with alpha-human thrombin in blood. The determination of hirudin was performed by a sandwich ELISA, using polyclonal and monoclonal antibodies and the chromogenic thrombin substrate assay. The alpha-human thrombin-hirudin complex concentration in the plasma of rhesus monkeys was measured over a period of 48 hours. The results of a sandwich ELISA were compared with those of the chromogenic thrombin substrate assay. A good agreement between the total hirudin concentrations analyzed by the hirudin ELISA and the alpha-human thrombin-hirudin complex ELISA and those of the chromogenic thrombin substrate assay, measuring total hirudin, too, was observed.

Influence of seasonal biorhythms on urinary excretion of enzymes and other parameters.

Urinary excretion of enzymes, electrolytes, creatinine, protein and the consumption of food and water in female and male Wistar rats was examined over two seasons of summer and wintertime, respectively. The evaluation of data revealed that gamma-glutamyltransferase, inorganic phosphate, and the lysosomal enzymes, N-acetyl-beta-D-glucosaminidase and acid phosphatase, were significantly different between the collection periods in both seasons. Other parameters showed significant differences only in male rats, whereas urinary electrolytes, with the exception of chloride, showed no significant differences.

Absence of interaction between ramipril, a new ACE-inhibitor, and phenprocoumon, an anticoagulant agent.

In a double-blind, placebo-controlled crossover trial, the effects of ramipril, a long-acting non-sulphydryl angiotensin I converting enzyme inhibitor, on phenprocoumon steady-state pharmacodynamics were investigated in 8 healthy male volunteers taking individually fixed doses of phenprocoumon. The results showed that 5 mg ramipril or placebo once daily for 7 days did not alter the anticoagulant response (Quick values) to phenprocoumon after a stabilization phase of 2 weeks. Mean Quick values during the steady-state phase with ramipril and placebo were 67.5% and 69.3%, respectively. The clotting factors II, VII, IX and X as well as protein C decreased in the run-in phase and remained stable both during ramipril and placebo treatment. There were no differences between ramipril or placebo treatments. As the phenprocoumon dosage was kept unchanged during the double-blind phase, the results indicate that ramipril does not interfere with the vitamin K-dependent cascade.

Pharmacodynamic effects of a single 10-mg dose of the angiotensin converting enzyme inhibitor ramipril in patients with impaired renal function.

A single oral 10-mg dose of ramipril, a long-acting angiotensin converting enzyme (ACE) inhibitor, was given to 24 hypertensive patients with different degrees of renal function. Creatinine clearance ranged from below 15 ml/min (n = 9) to above 80 ml/min (n = 3). Serial blood samples were taken for the determination of ACE activity, plasma renin activity (PRA), aldosterone (ALDO), angiotensin II (AT II), and serum creatinine (CR). Blood pressure was also monitored before and after medication. After administration of ramipril systolic and diastolic blood pressure (BP) fell; the decreases were unrelated to renal function. Peak BP-lowering effect was seen at 6 h basal, 174 +/- 19.5/102.6 +/- 8.9 to 149.8 +/- 19.7/87.6 +/- 13.3 mm Hg (mean +/- SD; p less than 0.001). ACE inhibition occurred within 2 h, being maximal at 4 h: basal, 82.6 +/- 17.9 to 0.2 +/- 0.6 nmol/ml/min (p less than 0.001). The greater the renal impairment, the longer the ACE inhibition. Angiotensin II was reduced maximally at 10 h after dosing, from 10.4 +/- 5.4 to 6.2 +/- 3.6 pg/ml (p less than 0.01). Aldosterone also fell from 212 +/- 188.4 to 134 +/- 73.3 pg/ml at 6 h (p less than 0.01). Plasma creatinine was unchanged: 401.3 +/- 315.7 to 394.9 +/- 306.1 nmol/L (NS). Ramipril, given as a single oral dose, lowers BP in hypertensives with both normal and impaired renal function, inhibits ACE activity, and causes no change in serum creatinine.

Recommendation for the measurement of "alanine aminopeptidase" in urine.

A method is recommended for the measurement of the catalytic concentration of alanine aminopeptidase in the urine of man, rat, and dog, using L-alanine-4-nitroanilide as substrate. In currently used methods, substrate concentrations between 1.7 and 2.0 mmol/l are used. Kinetic experiments show, however, that the reaction is inhibited by substrate concentrations exceeding 0.8 (man), 0.3 (rat) and 0.5 mmol/l (dog); these concentrations lie in the range of the Km values. Assay conditions were therefore chosen to give the lowest possible Km. The Km value depends on the type of buffer, and it increases with pH and temperature. The recommended assay conditions are: triethanolamine buffer 70 mmol/l, pH 7.6; L-alanine-4-nitroanilide concentrations depending on the species; incubation temperature 25 degrees C.

Absence of crystalluria and estimation of renal parameters after oral and intravenous ofloxacin as compared to placebo in healthy volunteers.

An open placebo-controlled study on eleven healthy male volunteers was carried out to investigate renal tolerance and the possibility of crystalluria after oral and intravenous administration of ofloxacin. Subjects received single doses of 200 and 400 mg ofloxacin orally, 200 mg ofloxacin intravenously, or placebo. Urine was collected in several fractions on each study day and the urine volume, excretion of ofloxacin, and excretion of creatinine, alanine aminopeptidase, N-acetyl-beta-D-glucosaminidase, and gamma-glutamyltransferase were calculated in each fraction collected. Furthermore, the urine was investigated microscopically to determine whether ofloxacin crystals were present. Serum creatinine and creatinine clearance were also calculated. No relevant changes in creatinine clearance were observed and no drug crystals were found in the urine which indicates that renal tolerance was good. There were no differences in ofloxacin recovery after oral or intravenous administration, confirming that absolute bioavailability of the oral form is excellent.

Renal tolerance of cefpirome (HR 810), a new cephalosporin antibiotic.

An open study was carried out in ten healthy, male volunteers in order to investigate the renal tolerance of cefpirome (HR 810), a new cephalosporin antibiotic. Subjects received a single dose of 1.0 g of cefpirome and then repeated doses of 1.0 g of cefpirome twice daily for five days. Urine was collected in several fractions during the study and the urine excretion, excretions of creatinine, N-acetyl-beta-D-glucosaminidase, gamma glutamyltransferase, alanine aminopeptidase and lactate dehydrogenase were calculated in 12-hour fractions. Serum creatinine (using an enzymatic method), beta 2-microglobulin concentrations and creatinine clearance were also determined. Based on the findings of these renal enzymes, renal tolerance was good. This was also confirmed by creatinine clearance calculations and follow-up of serum beta 2-microglobulin levels. Cefpirome showed good renal tolerance without any signs of nephrotoxicity in this study with the methods used.

Interference by the new antibiotic cefpirome and other cephalosporins in clinical laboratory tests, with special regard to the "Jaffé" reaction.

The new cephalosporin, cefpirome, was investigated for its possible interference in clinical laboratory tests, especially the determination of creatinine. Tests for bilirubin, cholesterol, protein, urea, and uric acid were also studied. A selection of commercially available compounds such as cefoperazone, cefazolin, cefamandole, cefoxitin, latamoxef, ceftriaxon, cefotiam, cephaloridine, cephalotin, cefotaxime, cefazedone and cefuroxime, and cefodizime (a compound under development) were also included in these investigations. Interference was found only with the "Jaffé method" for the determination of creatinine. Pronounced interactions with alkaline picrate were observed with cefpirome, cefoxitin, cephalotin and cephaloridine, whereas the other compounds showed only weak reaction or no reaction at all. The cephalosporins did not interfere in any of the other tests mentioned above. Care must therefore be taken in the determination of creatinine in samples from patients under treatment with these drugs. The assay methods of choice at present are enzymatic or specific HPLC assays.

The excretion of renal enzymes during rest and exercise: a double-blind comparison between placebo and penbutolol.

A double-blind cross-over study was carried out in five healthy male volunteers to investigate the renal tolerance of 40 mg penbutolol, a receptor-specific beta-blocking agent, during exercise and to compare its effects with a placebo. The effects of exercise were compared with a resting state after a medication on the placebo. Urine was collected in fractions for seven hours on each trial day. The urine volume and the excretion of alanine aminopeptidase (AAP), N-acetyl-beta-D-glucosaminidase (NAG) and gamma glutamyltransferase (GGT) per fraction were determined. The findings for the kidney enzymes AAP, NAG and GGT show that the renal tolerance of penbutolol was good. Physical exercise per se did not cause any increase in the excretion of the above-mentioned enzymes. Slight diurnal variation was seen in the excretion of the renal enzymes after both the placebo and penbutolol.

Dose linearity and other pharmacokinetics of cefodizime after single-dose intravenous administration.

Pharmacokinetics of cefodizime, a broad-spectrum cephalosporin antibiotic, were determined after intravenous (IV) administration of single doses of 1.0, 1.5, and 2.0 gm to 12 healthy male volunteers in an open study. In a separate pilot study, data were obtained after IV administration of 0.5 gm of cefodizime to six healthy male volunteers. Determinations of cefodizime in serum and urine using a microbiological assay agreed with determinations using high-pressure liquid chromatography (HPLC), which specifically measures the unchanged drug. Active metabolites of cefodizime were not detected. After IV administration of 1.0, 1.5, and 2.0 gm of cefodizime, initial mean serum concentrations were 215, 322, and 394 mg/L, respectively (HPLC determinations). A linear response to dosage was shown (coefficient of correlation r = .89), as was the case for area under the serum concentration-time curve to infinity, AUC infinity (r = .82), and 48-hour urinary recovery of cefodizime (r = .94). In all cases, the corresponding values obtained after the 0.5-gm dose showed that the linearity extended to this dose. The kinetics of single-dose administration of cefodizime corresponded to a two-compartment open model with an apparent steady-state volume of distribution of about 40 L. Volume of distribution, terminal elimination half-life, serum and renal clearance, and percent urinary recovery were not dose dependent. Cefodizime combined a long terminal elimination half-life (mean, 2.5 hours) with a high urinary recovery (80%). After IV administration of cefodizime, urinary concentrations of the unchanged drug remained above 5 micrograms/ml for at least 24 hours after drug administration and were dose dependent. Mean values for the 1.0-gm and 2.0-gm doses were, respectively, approximately 12 mg/L and 30 mg/L, several times the minimal inhibitory concentrations (MIC90) for most clinically relevant bacteria. These results suggest that once- or twice-daily IV dosing with cefodizime (depending on the dose regimen) would be suitable for clinical use. The drug was safe and well tolerated.

Absence of interaction between ofloxacin and phenprocoumon.

The effect of ofloxacin on steady-state phenprocoumon pharmacodynamics was investigated in 7 healthy male volunteers taking daily sub-therapeutic doses of phenprocoumon. Ofloxacin 200 mg once daily for 7 days did not alter the anti-coagulant response (Quick values) to phenprocoumon after a stabilization phase of 2 weeks. Mean Quick values during the steady-state phase before and during ofloxacin administration were 54% and 52%, respectively. In vitro studies with concentrations of 0 to 100 mg ofloxacin/1 added to plasma also failed to show any interaction. The results indicate, therefore, that ofloxacin does not interfere with vitamin K-dependent coagulation cascade, as seen after other antibiotics.

Identification of inhibitors of urinary alanine aminopeptidase.

Amino acids and ammonia were identified as natural inhibitors of urinary AAP. In urines from healthy volunteers approximately one half of the inhibition could be accounted for by amino acids and ammonia. At the measured concentrations, histidine, ammonia and phenylalanine, in decreasing order, were the most effective inhibitors. Results from kinetic studies with amino acids added to gel-filtered urine are consistent with the presence of two AAP isoenzymes with different inhibition characteristics. The ten amino acids which were tested show the same inhibition kinetics. Differences between amino acids are quantitative.

Enzymuria in streptozotocin-diabetic rats.

Twenty four hour urine samples of male control and streptozotocin-diabetic Wistar rats were analysed for a series of commonly known kidney-specific enzymes, for electrolytes, creatinine, glucose, total protein and urine volume. The examination was done during two periods of 5 days between the 25th and 30th and the 32nd and 36th day after streptozotocin application. In the first period the animals had free access to food and water, whereas in the second period on days 32, 34 and 36 food was withdrawn. In the first observation period the diabetic rats showed increased excretion rates of 15 measured urinary parameters, while alanine aminopeptidase (EC 3.4.1.2) and gamma-glutamyltransferase (EC 2.3.2.2) activities were lowered and inorganic phosphate was unchanged. The removal of food resulted in decreased excretion values for alanine aminopeptidase, gamma-glutamyltransferase and total protein as compared with fasted nondiabetic animals. The activities of N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30), acid phosphatase (EC 3.1.3.2), lactate dehydrogenase (EC 1.1.1.27), pyruvate kinase (EC 2.7.1.40), C1-fructose 1.6-diphosphatase (EC 3.1.3.11) and the excretion values for sodium, calcium, magnesium, chloride and glucose were higher than in fasted nondiabetic rats. beta-Glucosidase (EC 3.2.1.21), potassium, inorganic phosphate, creatinine, and urine volume showed no differences between fasted diabetic and fasted control animals. The enzymes in the renal cortex at the end of the experiment showed only decreased activity of alanine aminopeptidase in diabetic rats. Lactate dehydrogenase, pyruvate kinase, beta-glucosidase, C1-fructose 1.6-diphosphatase and glucose 6-phosphatase (EC 3.1.3.9) were increased and gamma-glutamyltransferase, N-acetyl-beta-D-glucosaminidase, acid phosphatase and glucose 6-phosphate dehydrogenase (EC 1.1.1.49) showed no change.(ABSTRACT TRUNCATED AT 250 WORDS)