The in vitro pharmacological profile of KR31080, a nonpeptide AT1 receptor antagonist

Summary— KR31080 (2-butyl-5-methyl-6-(1-oxopyridin-2-yl)-3-[[2'-(1H-tetrazol-5-yl) biphenyl-4-yl]methyl]-3H-imidazo[4,5-b] pyridine) is a potent inhibitor of angiotensin type 1 (AT₁) receptors in rabbit aorta and human recombinant AT₁ receptors. In the isolated rabbit thoracic aorta, KR31080 caused a nonparallel shift to the right of the concentration-response curves to angiotensin II (All) with decreased maximal response (pD'₂ = 10.1 ± 0.1), but had no effect on the contractile response induced by norepinephrine. KR31080 inhibited specific [¹²⁵I]AII binding to rabbit aortic membranes (AT, receptors) and [¹²⁵I][Sar¹, Ile⁸]AII binding to human recombinant AT₁ receptors in a concentration-dependent manner with IC₅₀ values of 0.84 ± 0.08 nM and 1.92 ± 0.15 nM, respectively, but did not inhibit specific [¹²⁵I)AII binding to bovine cerebellum membranes (ÀT₂ receptors). In the Scatchard analysis, KR31080 interacted with rabbit aortic AT₁ receptors in a competitive manner, similar to losartan. These results demonstrate that KR31080 is a potent and AT₁ selective angiotensin receptor antagonist which exerts a competitive antagonism in the [¹²⁵I]AII binding assay and insurmountable AT₁ receptor antagonism in the functional study.     

A Chinese adolescent girl with Fechtner-like syndrome

We describe a 15-y-old girl with Fechtner-like syndrome, who is the first Chinese reported to have this rare syndrome. She presented with left homonymous hemianopia and neuroimaging revealed haemorrhage in both parietal and occipital lobes. Peripheral blood smear showed macrothrombocytopenia and intracytoplasmic inclusion bodies inside leucocytes. Thrombocytopenia and proteinuria responded to intravenous immunoglobulin and pulsed methylprednisolone. This case illustrates that life-threatening haemorrhage can occur in patients with Fechtner syndrome. Although there was no effective treatment reported in the literature, high dose steroid and immunoglobulin seemed to be useful in our patient. Our patient also had nephritic-nephrotic syndrome with renal insufficiency, which is unusual in adolescent female patients.     

Effects of glucocorticoids on lung glutamine and alanine metabolism

The role of the glucocorticoid hormones as possible mediators of the accelerated lung glutamine and alanine release that occurs during critical illness was investigated. Studies were done in adult rats receiving dexamethasone (0.6 mg intramuscularly/100 gm body weight/day for 2 consecutive days; n = 24) or saline solution (controls; n = 20). Measurements were made in the postabsorptive state and amino acid flux was calculated by multiplying pulmonary blood flow by the right ventricular-arterial concentration difference for glutamine and alanine. Lung glutamine release was 703 +/- 184 nmol/100 gm body weight/min in control rats. This release rate doubled in the dexamethasone-treated rats (1476 +/- 256; p less than 0.05). The activity of the glutamine synthetase enzyme increased by 33% in the dexamethasone-treated animals and there was a 50% decrease in lung glutamine content (p less than 0.01). Likewise, dexamethasone accelerated the release of alanine by the lungs twofold (559 +/- 173 nmol/100 gm body weight/min in controls vs 1113 +/- 184 nmol/100 gm body weight/min in dexamethasone-treated rats; p less than 0.05). The increased release of both amino acids was caused by a significant increase in the concentration difference across the lungs and not a change in pulmonary blood flow. Glucocorticoids appear to be key mediators of the accelerated lung amino acid release that characterizes catabolic diseases.     

The effect of methylprednisolone treatment on the cardiopulmonary bypass-induced systemic inflammatory response.

OBJECTIVE: Cardiac surgery with cardiopulmonary bypass (CPB) is associated with an inflammatory response caused by contact of blood with artificial surfaces of the extracorporeal circuit, ischemia-reperfusion injury, and release of endotoxin. The inflammatory reaction involves activation of complement leucocytes, and endothelial cells with secretion of cytokines, proteases, arachidonic acid metabolites, and generation of oxygen derived free radicals (OFR) by polymorphonuclear neutrophils (PMN). Although this inflammatory response to CPB often remains at subclinical levels, it can also lead to major organ dysfunction. A number of studies have demonstrated that treatment of patients with a high-dose (30 mg/kg) of corticosteroids (methylprednisolone) attenuates the CPB-induced SIR and improves the outcome of patients undergoing cardiac surgery. However, large doses of steroids can cause abnormal metabolic responses such as metabolic acidosis and hyperglycemia. In the present study, we examined the efficacy of low doses of methylprednisolone (5 and 10 mg/kg) to attenuate the CPB-induced inflammatory response, during and after heart operations. METHODS: Thirty-six adult patients undergoing cardiac surgery, were randomized into three groups: (1) control group: group A; (2) methylprednisolone, 5 mg/kg body weight: group B; and (3) methylprednisolone, 10 mg/kg body weight: group C. Plasma levels of the cytokines interleukin-6 (IL-6) and TNF-alpha were analyzed by enzyme-linked immunosorbent assay, before, during, and after CPB. OFR production was determined by cytofluorometry (FACS) at the same end points. RESULTS: No significant differences in age, body weight, CPB time, and cross-clamp time were observed among the three groups. CPB induced a marked increased in cytokine release and OFR generation. Low-dose of methylprednisolone (5 mg/kg) effectively reduced the increase in TNF-alpha and IL-6 secretion (P<0.05 compared to control group) after release of the cross-clamp. However, OFR generation was significantly reduced with a greater dose of methylprednisolone (10 mg/kg). CONCLUSIONS: The results indicate that a single low-dose of methylprednisolone (10 mg/kg) reduces the inflammatory reaction during and after CPB, by inhibition of proinflammatory cytokine release and OFR generation after release of the aortic cross-clamp.     

Cyclosporine interactions with miconazole and other azole-antimycotics: a case report and review of the literature.

Several antimicrobial drugs have been shown to pharmacokinetically interact with cyclosporine. On two separate occasions, we observed increases in cyclosporine plasma concentrations during concomitant miconazole therapy in a heart transplant patient with an infection secondary to Pseudallescheria boydii. To our knowledge, no interaction between cyclosporine and miconazole has previously been reported. In addition, drug interactions were observed between cyclosporine and ketoconazole and possibly between cyclosporine and SCH 39304, an investigational azole-antifungal agent. No interaction was noted between cyclosporine and fluconazole. In general, clinicians should anticipate drug interactions between cyclosporine and azole-antimycotic agents.