Orlistat reduces gallbladder emptying by inhibition of CCK release in response to a test meal.

BACKGROUND AND AIMS: Orlistat is a covalent inhibitor of digestive lipase derived from lipstatin, the natural product of Streptomyces toxytricini. By blocking the active site of intestinal lipase, orlistat inhibits hydrolysis of dietary triglycerides and thus reduces the intestinal lipid absorption. It is uncertain whether intestinal inhibition of lipase by orlistat also interferes with nutrient-induced CCK release from intestinal I-cells. The aim of the present study was therefore to assess whether oral administration of orlistat inhibits CCK release in response to a test meal and thus causes impaired gallbladder emptying. METHODS: 22 healthy volunteers were given a test meal consisting of 200 ml dairy cream and two teaspoons of chocolate powder (552 kcal=2328 kJ; 56.0 g fat; 5.2 g proteins, 6.6 g carbohydrates), with and without oral application of 120 mg orlistat. Gallbladder volume was determined by ultrasound before and 5, 10, 20, 30 and 40 min after meal ingestion. In parallel, a venous blood sample was collected for the measurement of bioactive CCK. CCK activity was assessed using a bioassay with isolated rat pancreatic acini cells. RESULTS: Oral administration of orlistat significantly impairs gallbladder emptying. After ingestion of the test meal the gallbladder contracted by 78.5% in the control group, whereas the test group with orlistat only showed a contraction of 45.7% (p<0.01). Maximal contraction was reached after 35 to 40 min, the maximal gallbladder emptying was delayed up to 10 min by orlistat. Orlistat induced a significant reduction of bioactive CCK levels in response to a test meal (CCK(max) with orlistat=4.1 pmol/l; CCK(max) without orlistat=7.8 pmol/l). CCK levels were reduced by 47% and the onset of maximal CCK secretion was delayed up to 10 min. CONCLUSION: The inhibition of intestinal lipolytic activity by orlistat results in reduced gallbladder emptying through inhibition of meal-mediated CCK release. We therefore hypothesize that impaired gallbladder motility may represent a risk factor in chronic treatment of severe obesity using orlistat.

Fluoroquinolone-associated anaphylaxis in spontaneous adverse drug reaction reports in Germany: differences in reporting rates between individual fluoroquinolones and occurrence after first-ever use.

BACKGROUND: The frequency of fluoroquinolone-associated anaphylaxis has been estimated to be 1.8-23 per 10 million days of treatment based on spontaneous reports. It is unknown whether there are differences between the reporting rates of anaphylaxis with individual fluoroquinolones. According to pathophysiology, anaphylaxis may be immune mediated (anaphylactic) or not (anaphylactoid). The latter may occur after first-ever intake since no sensitisation phase is necessary. OBJECTIVE: To analyse spontaneous reports of fluoroquinolone-associated anaphylaxis contained in the spontaneous adverse drug reaction database of the Federal Institute for Drugs and Medical Devices in Germany with regard to differences in reporting rates between various fluoroquinolones, the previous intake and the time to onset of the reaction. METHODS: All fluoroquinolone-associated cases of anaphylaxis, anaphylactic shock, and anaphylactic/anaphylactoid reaction spontaneously reported to the Federal Institute for Drugs and Medical Devices between 1 January 1993 and 31 December 2004 were identified and assessed with regard to the correctness of the diagnosis of anaphylaxis, the causal relationship with the drug, the previous intake of fluoroquinolones and the time to onset of the reaction. RESULTS: In 166 of 204 cases identified, the diagnosis of anaphylaxis and a causal relationship with the drug were considered at least possible. Moxifloxacin, levofloxacin, ciprofloxacin and ofloxacin accounted for 90 (54%), 25 (15%), 21 (13%) and 16 (10%) of the 166 cases, respectively. The corresponding reporting rates per 1 million defined daily doses based on crude estimates of exposure were 3.3, 0.6, 0.2 and 0.2 for moxifloxacin, levofloxacin, ciprofloxacin and ofloxacin, respectively. The occurrence of anaphylaxis after the first dose or within the first three days was reported in 71 of 166 (43%) cases, but no information on prior exposure with this or any other fluoroquinolone was provided with these reports. In 21 of 166 (13%) cases, the reaction occurred within the first 3 days and it was stated that the particular fluoroquinolone had never been taken before. CONCLUSIONS: Anaphylaxis appears to be associated with the fluoroquinolone class of antibacterials. Observed differences in reporting rates should be further investigated. Fluoroquinolone-associated anaphylaxis may occur after first-ever intake of the agent.

Inhibition of phospholipase C-independent exocytotic responses in rat peritoneal mast cells by U73122.

UNLABELLED: The aminosteroid U73122 has been established as potent, selective, and cell-permeable inhibitor C-type phosphatidylinositol-specific phospholipases (PI-PLCs), and has been used to define a contribution of PI-PLCs as part of exocytotic signalling pathways in rat peritoneal mast cells (RPMCs). However, doubts have been raised regarding its PI-PLC selectivity of action. Therefore, in the present study, U73122 was tested in RPMCs under experimental conditions allowing to elicit exocytosis PI-PLC independently (streptolysin O [SLO]-permeabilised cells; stimulated by GTPgammaS; in the presence of low concentrations of free Ca2+). The release of [3H]5-hydroxytryptamine ([3H]5-HT) from [3H]5-HT-loaded RPMCs served as measure of secretion. U73122 potently inhibited the exocytotic response induced by 10 microM GTPgammaS (Ca2+: 10(-6) M) in permeabilised cells (IC50: 0.6 microM, n=5) in an insurmountable manner. In intact RPMCs, with a nearly equal potency (IC50: 4 microM, n=4), U73122 also inhibited the PI-PLC-dependent exocytotic response induced by concomitant application of nerve growth factor and lyso-phosphatidylserine (NGF/lyso-PS). CONCLUSION: U73122 exerts potent PI-PLC-independent secretostatic effects, limiting its use to define PI-PLC function within exocytotic processes.

Pharmacological inhibition of outwardly rectifying Cl- currents in rat peritoneal mast cells: a comparison of different stilbene derivatives.

Diethylstilbestrol and other stilbene derivatives can provide some inhibition of the outwardly rectifying Cl- current (I(Cl-,OR)) in rat peritoneal mast cells. In order to elucidate structure-activity relationships of diethylstilbestrol, 12 stilbenes as well as 17beta-estradiol and hexestrol were tested in rat peritoneal mast cells using the nystatin-perforated patch approach of the whole-cell patch-clamp technique. Since trans-stilbene showed no effect, the substituents of diethylstilbestrol must be of importance. The introduction of only one hydroxy group in trans-stilbene produced potent inhibition of the I(Cl-,OR) (IC50: 3.3 microM). But in contrast, resveratrol with hydroxy groups at positions 4, 3', and 5' as well as methoxy substituted stilbene derivatives and 17beta-estradiol were ineffective. On the other hand, hexestrol potently inhibited I(Cl-,OR) indicating that the aromatic ring systems can also be connected by an ethyl bridge. In summary, a hydroxy group at position 4 (or 4') is a prerequisite for diethylstilbestrol-mediated inhibition of I(Cl-,OR).

The vasorelaxant effect of pituitary adenylate cyclase activating polypeptide and vasoactive intestinal polypeptide in isolated rat basilar arteries is partially mediated by activation of nitrergic neurons.

The structurally related neuropeptides pituitary adenylate cyclase activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) are recognised by two G protein-coupled receptors, termed VPAC(1)-R and VPAC(2)-R, with equal affinity. PACAP and VIP have previously been shown to relax cerebral arteries in an endothelium-independent manner. The aim of the present study was to test if intramural neurons are involved in the mediation of PACAP/VIP-induced vasodilatory responses. Therefore, the vascular tone of isolated rat basilar arteries was measured by means of a myograph. The vasorelaxing effect of PACAP was assessed in arteries precontracted by serotonin in the absence or presence of different test compounds known to selectively inhibit certain signaling proteins. The vasorelaxant effect of PACAP could be significantly reduced by the inhibitor of neuronal N-type calcium channels omega-conotoxin GVIA (omega-CgTx), as well as by 3-bromo-7-nitroindazole (3Br-7-Ni), an inhibitor of the neuronal nitric oxide-synthase (nNOS). The localization of N-type calcium channels and VPAC-Rs within the rat basilar artery was investigated by confocal laser scanning microscopy using omega-CgTx- and VIP-analogs labelled with fluorescent dyes. These findings suggest that activation of intramural neurons may represent an important effector mechanism for mediation of the vasorelaxant PACAP-response.

The outwardly rectifying chloride channel in rat peritoneal mast cells is regulated by serine/threonine kinases and phosphatases.

A slowly activating, outwardly rectifying Cl- channel (ORCC) has been described in rat peritoneal mast cells (RPMCs). This channel is activated by intracellular application of cAMP, an effect that might be mediated by a PKA-type serine/threonine protein kinase. To test this hypothesis, whole-cell patch-clamp experiments (nystatin-perforated patch) were performed and 8-bromoadenosine 3',5'-cyclic monophosphothioate, Sp-enantiomer (Sp-8Br-cAMPS), a cell membrane-permeable activator of PKA, and three inhibitors of different serine/threonine protein phosphatases (okadaic acid, cantharidin, calyculin A), were tested. In RPMCs application of repetitive series of step hyper- and depolarizations (holding potential 0 mV, test potentials -80 to +80 mV, step size +20 mV) induced a slowly increasing, [half-maximal activation time ( t0.5) 11.0+/-1.1 min, Imax (at +80 mV) 18.7+/-3.1 pA pF-1], DIDS-sensitive, outwardly rectifying Cl- current I(Cl,OR). The activation of this current could be accelerated by Sp-8Br-cAMPS, okadaic acid or cantharidin in the extracellular solution. Co-application of Sp-8Br-cAMPS and okadaic acid increased Imax supra-additively. Calyculin A and higher concentrations of cantharidin inhibited the Cl- current via unknown mechanisms. Our findings suggest that I(Cl,OR) in RPMCs is activated by a PKA-type protein kinase, a process which is antagonized functionally by okadaic acid- and cantharidin-sensitive protein phosphatases.