Inactivation of endothelin by polymorphonuclear leukocyte-derived lytic enzymes.

Cultured bovine aortic endothelial cells (BAEC) released endothelin-1 (ET-1) in the culture medium in a time-dependent fashion. Coincubation of fMLP-activated human polymorphonuclear leukocytes (PMN) with BAEC caused a fast (maximal activity was reached within 15 minutes) and cell number-dependent disappearance of ET-1 from the medium. This effect was direct to ET-1, because it was also present when PMN were incubated with the synthetic peptide in the absence of BAEC. PMN-dependent disappearance of ET-1 was associated with loss of constrictor activity on isolated rabbit aorta. PMN-released products were responsible for ET-1 degrading activity, because supernatants of activated PMN were equally effective as the intact cells. Resting PMN, in the same time frame, were uneffective. Eglin C, a potent blocker of PMN-derived elastase and cathepsin G, reversed the ET-1 inhibitory activity of fMLP-stimulated PMN and of their supernatant. Direct addition of elastase and cathepsin G to synthetic ET-1 destroyed its immunoreactivity and this effect was blocked by eglin C. High-performance liquid chromatography (HPLC) analysis supported the hypothesis that ET-1 degradation by PMN was due to enzymatic proteolysis. These data provide evidence that activated PMN are able to degrade ET-1 through the release of proteases. Because physiologic concentrations of PMN can destroy high amounts (up to 100 nmol/L) of ET-1 within a few minutes, we propose that this mechanism of ET-1 inactivation has biologic relevance.

Absorption, disposition, and urinary metabolism of 14C-rifabutin in rats.

14C-rifabutin was given orally (25 mg/kg) and intravenously (i.v.) (10 mg/kg) to female Sprague-Dawley rats. Radioactivity was eliminated by both the renal and fecal routes, amounting to 44.49 and 43.39% of the dose, respectively, in urine and feces at 96 h after the oral dose and to 47.81 and 40.76% of the dose, respectively, in urine and feces after the i.v. dose. Differences between the two routes of administration were negligible. Tissue distribution of radioactivity after the oral dose was investigated by the combustion technique. At 2 h, the highest concentration of radioactivity was observed in the liver, followed by the lung, abdominal adipose tissue, and spleen, whereas at 72 h, the sequence was abdominal adipose tissue, liver, spleen, bone marrow, and lung. Brain levels of radioactivity were very low. The results of whole-body autoradiography after i.v. administration confirmed the above. Whole-body autoradiography of pregnant rats showed higher concentrations of radioactivity in the uterus than in the placenta and trace levels in the fetuses up to 8 h. Radioactivity was absent in the amniotic fluid. The urinary metabolism was studied by radio-high-pressure liquid chromatography. Rifabutin accounted for 7.4 and 7.2% of the dose in 0- to 48-h urine after oral and i.v. administration, respectively. Metabolites 31-OH rifabutin and 25-O-deacetyl rifabutin amounted to 4.3 and 1.6% of the dose, respectively, after oral administration and to 2.6 and 0.7% of the dose, respectively, after i.v. administration. The remaining urinary radioactivity was mainly due to polar compounds.

Disposition of 14C-labelled FCE 22101 in animals.

14C-FCE 22101 was given intravenously to rats (4, 16 and 38 mg/kg), dogs (69 mg/kg), rabbits (99 mg/kg) and monkeys (41 and 99 mg/kg). Radioactivity was eliminated mainly in urine, with faecal excretion being less than 10% in all animal species. Radioactivity as expired 14CO2 was detected in the rat and accounted for less than 0.5% of the dose in 24 h. Tissue distribution was also investigated in the rat (38 mg/kg). After combustion and radioactivity counts the highest concentration of radioactivity was observed in the kidneys, followed by the lung, the skin and hair, and lastly by the liver and adrenals. Brain levels of radioactivity, corrected for blood contamination, were 40 to 60 times lower than the corresponding blood levels. The results of whole body autoradiography confirmed those above. Whole body autoradiography of pregnant rats did not show any transfer of radioactivity into fetuses and only low radioactivity was present in the placenta.

Pharmacokinetics and metabolism of a new beta-adrenergic blocking agent, the 1, ter-butyl-amino-3-(1,2,3,4-tetrahydro-1,4-ethano-8-hydroxy-5-naphthoxy)-2-propanol (K 5407).

A beta-blocking agent, the 1,ter-butylamine3-(1,2,3,4-tetrahydro-1,4-ethano-8-hydroxy-5-naphthoxy)-2-propanol (K5407) was synthesized with 14C and 3H and its pharmacokinetics in the dog and man were investigated after i.v. and oral administration. K5407 was rapidly absorbed after oral dosing and plasma peaks were within 1 hour. Concentrations of unchanged compound were found to be very small. After i.v. injection the levels decreased with a half-life of 2-3 hours. Excretion was mainly in the urine and amounted to about 72% of the dose in the dog and about 85% in man for both administration routes. Tissue radioactivity distribution studies in male and in pregnant mice after i.v. injection showed rapid body diffusion, passage through the blood-placenta barrier and no localization in the central nervous system. The metabolic process in dog and human urine was studied. Little unchanged compound was found (5% in the dog and 13% in man after i.v. injection and about 1% in both species after oral dosing). Conjugation processes represented the main route of biotransformation. Five metabolites, resulting from side chain degradation of the compound, were identified in dog urine and in trace quantities in human urine.

Pharmacokinetics and metabolism of indoprofen in the hamster.

2-[p-(1-Oxo-2-isoindolinyl)phenyl]propionic acid (indoprofen) is rapidly absorbed after oral administration (2 mg/kg) to male and female hamsters. Peak plasma levels of about 12-13 microgram/ml are reached within 1 h of dosing. Plasma concentrations in males and females are similar until 4 h but different at subsequent observation times. The half-life of indoprofen in plasma is approximately 7 h for males and 16 h for females. In experiments with 14C-labelled compound, radioactivity is mainly excreted in the urine: 94% of the dose in 6 days for males and 73% in 5 days for females. The females also excrete a significant amount of the drug (22%) in the faeces, probably via the bile. Residual radioactivity in female carcasses on the 5th day represents 1% of the dose. The main excretory product is the unchanged drug as such (about 35% and 21%, respectively, in 0-24 hour urine for males and females) and as glucuronic acid conjugate (29% and 12%). Small amounts of 5- and 6-hydroxy-isoindolinyl derivatives, and of two metabolites whose structures have not been identified, are also found in the urine of the animals of both sexes.

Tissue distribution of 14C-indoprofen in the rat.

The tissue distribution of 14C-labelled 2-[p-(1-oxo-2-isoindolinyl)phenyl)propionic acid (indoprofen) after i.v. injection was studied in male and pregnant rats by whole-body autoradiography. Distribution was characterized by a rapid localization in the liver, kidneys and lungs. A significant amount of radioactivity found in the intestinal contents suggested biliary excretion. There was no indication of retention of the drug in the brain. In pregnant rats, radioactivity crossed the blood-placenta barrier to a moderate extent and low concentrations were found in foetuses.