Vasorelaxant effect of olprinone, an inhibitor of phosphodiesterase 3, on mesenteric small artery and vein of rabbits

Differential vasodilation response to olprinone in rabbit renal and common carotid arteries

PURPOSE

Olprinone, one of the most frequently used phosphodiesterase-3 inhibitors, exerts its positive inotropic and vasodilation effects by inhibiting the degradation of intracellular cyclic adenosine monophosphate (cAMP). The vasodilation response to olprinone is not uniform among the different vascular beds. This study was designed to compare the vasorelaxation response to olprinone between renal and common carotid arteries, and investigate its underlying mechanisms.

METHODS

Isometric force measurement, enzyme immunoassay, and western blotting techniques were used to investigate the vasorelaxation action of olprinone in isolated rabbit renal and common carotid arteries.

RESULTS

Olprinone inhibited the contractile response to phenylephrine (PE) both in the renal and carotid arteries in a concentration-dependent manner with IC50 values of 40 +/- 10 and 103 +/- 43 nM, respectively. The IC50 value was lower (P = 0.004) and the maximal inhibition was greater (P = 0.002) in the renal artery compared with the carotid artery. A cell-permeable cAMP analogue, 8-bromo-cAMP, also inhibited the contractile response to PE in the renal and carotid arteries with IC50 values of 581 +/- 150 and 740 +/- 179 microM, respectively; however no differences were observed both in the IC50 value and the maximal inhibition between two arteries. Olprinone (0.1 microM) increased the intracellular cAMP level in the renal arterial smooth muscle cells (ASMCs) but not in the carotid ASMCs. The expression of PDE3A was greater (P = 0.008) in the carotid ASMCs than the renal ASMCs.

CONCLUSION

The enhanced vasodilator action of olprinone in the renal artery is presumably because of its ability to stimulate the cAMP production, which might be attributable to the heterogeneous expression of PDE3A.

The phosphodiesterase III inhibitor olprinone inhibits hippocampal glutamate release via a cGMP/PKG pathway

Olprinone, an inhibitor of cyclic nucleotide phosphodiesterase III, inhibited an increase in intracellular Ca(2+) concentrations for acutely dissociated rat hippocampal pyramidal neurons induced by extracellular high K(+) (35 mM) depolarization. Olprinone (100 microM) significantly reduced spontaneous glutamate release from rat hippocampal slices. Furthermore, olprinone significantly decreased the rate of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor-mediated miniature excitatory postsynaptic currents (AMPA-mEPSCs) monitored from CA1 pyramidal neurons of rat hippocampal slices, and the effect was blocked by KT5823, an inhibitor of protein kinase G (PKG), but not by H-89, an inhibitor of protein kinase A (PKA). In the PKA assay using PC-12 cells, olprinone did not activate PKA. Taken together, the results of the present study show that olprinone attenuates intracellular Ca(2+) rise through voltage-sensitive Ca(2+) channels and inhibits presynaptic glutamate release via a cGMP/PKG pathway.

Effects of olprinone on hepatosplanchnic circulation and mitochondrial oxidation in a porcine model of endotoxemia

PURPOSE

This study was performed in order to assess the effects of olprinone, a phosphodiesterase III inhibitor, on hepatic oxygen delivery (DO2H), oxygen consumption (VO2H), and mitochondrial oxidation in the liver of a porcine endotoxemia model.

METHODS

Fourteen pigs received continuous infusion of endotoxin via the portal vein for 240 min. From t = 150 to t = 240 min, animals were randomly divided into two groups to receive saline (control [CONT]; n = 7), or olprinone (OLP; n = 7) via the central vein.

RESULTS

In the OLP group, prior to olprinone treatment at 150 min, endotoxin induced significant decreases in the cardiac index (CI; from 120 +/- 31 to 65 +/- 13 ml.kg(-1).min(-1); P < 0.01) and DO2H (from 3.58 +/- 0.81 to 1.55 +/- 0.49 ml.kg(-1).min(-1); P < 0.01), while VO2H was maintained. After administration of olprinone (from t = 150 to t = 240 min), CI was unchanged, while DO2H increased from 1.55 +/- 0.49 to 1.93 +/- 0.38 ml.kg(-1).min(-1) (P < 0.01) and VO(2)H increased from 0.42 +/- 0.28 to 0.69 +/- 0.38 ml.kg(-1).min(-1) (P < 0.01). At t = 240 min, the oxidation level of cytochrome aa3 was significantly higher in the OLP group than in the CONT group (OLP, 66.2 +/- 19.3% vs CONT, 26.4 +/- 17.3%; P < 0.01).

CONCLUSION

Our data for this porcine endotoxemia model suggest that olprinone may have beneficial therapeutic effects in restoring not only systemic and hepatic circulation but also mitochondrial oxidation in the liver.

Capsaicin-induced, capsazepine-insensitive relaxation of the guinea-pig ileum

The mechanisms underlying transient receptor potential vanilloid receptor type 1 (TRPV1)-independent relaxation elicited by capsaicin were studied by measuring isometric force and phosphorylation of 20-kDa regulatory light chain subunit of myosin (MLC(20)) in ileum longitudinal smooth muscles of guinea-pigs. In acetylcholine-stimulated tissues, capsaicin (1-100 microM) and resiniferatoxin (10 nM-1 microM) produced a concentration-dependent relaxation. The relaxant response was attenuated by 4-aminopyridine and high-KCl solution, but not by capsazepine, tetraethylammonium, Ba(2+), glibenclamide, charybdotoxin plus apamin nor antagonists of cannabinoid receptor type 1 and calcitonin-gene related peptide. A RhoA kinase inhibitor reduced the relaxant effect of capsaicin at 30 microM. Capsaicin and resiniferatoxin reduced acetylcholine- and caffeine-induced transient contractions in a Ca(2+)-free, EGTA solution. Capsaicin at 30 microM for 20 min did not alter basal levels of MLC(20) phosphorylation, but abolished an increase by acetylcholine in MLC(20) phosphorylation. It is suggested that the relaxant effect of capsaicin at concentrations used is not mediated by TRPV1, but by 4-aminopyridine-sensitive K(+) channels, and that capsaicin inhibits contractile mechanisms involving Ca(2+) release from intracellular storage sites. The relaxation could be explained by a decrease in phosphorylation of MLC(20).

The cerebrovascular dilatation effects of olprinone, a phosphodiesterase III inhibitor, in comparison with acetazolamide—a pliot study

To examine the effects of olprinone, a phosphodiesterase III inhibitor, on cerebral blood flow (CBF), we compared the effects of olprinone on CBF to that of acetazolamide. Using technetium-99m-ethyl cysteinate dimer (99mTc-ECD) brain SPECT, we measured regional CBF (rCBF) at 33 sites, including 16 right and left pairs of non-infarct cerebral cortexes, in seven stroke patients (66.0+/-3.2 years) in a resting state and 15 min after the administration of acetazolamide. Within 1 week, rCBF at each site was measured 15 min after the initiation of olprinone infusion. Resting rCBF showed a significant negative correlation with the change in rCBF (DeltaCBF) during olprinone infusion (r = -0.43, P=0.013), but no significant correlation was seen following acetazolamide administration. The difference in rCBF between the right and left cortex increased more following acetazolamide administration (14.1+/-10.9 ml/(min 100 g)) than during olprinone infusion (5.4+/-4.8 ml/(min 100 g), P=0.013). The rCBF at four regions of interest (ROI) with low-resting CBF (< 49 ml/(min 100 g)) further decreased following the administration of acetazolamide. The vasodilatory effects of olprinone are dependent on resting CBF instead of on the intracerebral steal phenomenon that occurs with acetazolamide.

Improvement of cerebral blood flow by olprinone, a phosphodiesterase-3 inhibitor, in mild heart failure

Cerebral blood flow (CBF) is reduced in heart failure (HF). For the treatment of acute HF, a phosphodiesterase-3 inhibitor, olprinone (OL), yields an increase in myocardial contractility and a decrease in arterial afterload. During a 15-min intravenous infusion of OL (0.2 microg/kg/min), regional CBF at 6 sites of each cerebral cortex was examined using technetium-99m-ethylcysteinate dimer brain SPECT in 18 HF patients and 7 age-matched normal subjects. The baseline CBF was significantly reduced in HF (43.0 +/- 3.9 ml/min/100 g) compared to that in normal subjects (48.0 +/- 4.6 ml/min/100 g, p < 0.01). The baseline CBF showed a significant negative correlation with the increase in CBF during the OL infusion in HF (r = -0.38, p < 0.01) and normal subjects (r = -0.65, p < 0.01). The percent increase in CBF was significantly greater in HF (13.7%) than in normal subjects (9.8%, p < 0.046). In patients with HF, the CBF of the cerebral cortex was decreased, but was increased by OL infusion.

Olprinone: a phosphodiesterase III inhibitor with positive inotropic and vasodilator effects

Olprinone is a newly developed phosphodiesterase III inhibitor characterized by several properties. First, olprinone has positive inotropic and vasodilator actions and improves myocardial mechanical efficiency. Second, olprinone augments cerebral blood flow by a direct vasodilatory effect on cerebral arteries. The cerebrovascular reactivity to olprinone is marked in patients with impaired cerebral circulation. Third, olprinone selectively improves carotid artery distensibility, which may be attributable to differences in the arterial structural components or the reactivity of smooth muscle cells to olprinone. Fourth, olprinone improves inadequate redistribution of brain perfusion and may prevent cerebral metabolic abnormalities in heart failure.

Relaxation induced by milrinone and rolipram in human penile arteries and veins

We studied the relaxant effects of milrinone, an inhibitor of phosphodiesterase 3, and rolipram, an inhibitor of phosphodiesterase 4, on contracted human penile dorsal artery and deep dorsal vein. Vascular rings from 12 multi-organ donors were suspended in organ baths for isometric recording of tension. Both milrinone and rolipram inhibited (100%) the contraction induced by noradrenaline and shifted the relaxation-response curves to the cAMP forming agents prostaglandin E(1) and forskolin to the left. The findings indicate that the cAMP pathway appears to be a main determinant of relaxation in human penile vessels.

Effects of olprinone, a phosphodiesterase 3 inhibitor, on regional cerebral blood flow of cerebral cortex in stroke patients

The effects of olprinone (0.2 microg/kg per minute, i.v.) on cerebral blood flow were examined using technetium-99m-ethyl cysteinate dimer (99mTc-ECD) brain single-photon emission computed tomography in 14 stroke patients (69.0 +/- 5.6 years) and 12 normal subjects (68.1 +/- 6.2 years). The regional cerebral blood flow of the cerebral cortex was measured at six sites for each stroke patient (stroke group: n = 68, excluding 16 infarct areas confirmed on computed tomography image) and for each normal subject (normal group: n = 72). 99mTc-ECD brain single-photon emission computed tomography was repeated as the baseline 7 days after olprinone treatment study. The percent increment of the rCBF was 14.4 +/- 9.8% in the normal group and 10.7 +/- 11.7% in the stroke group (p = 0.002). The baseline value of the regional cerebral blood flow had a significant negative correlation with the increase of the regional cerebral blood flow in the normal group (r = -0.73, p < 0.0001) and in the stroke group (r = -0.43, p < 0.001). Although olprinone could dilate the cerebral vessels of stroke patients as well as those of normal subjects, smooth muscle dysfunction of the cerebral vessels due to advanced arteriosclerosis may reduce this effect.

The effects of olprinone (a phosphodiesterase III inhibitor) on hepatic vascular bed in a porcine model of endotoxemia

Decreased hepatic blood flow, and impaired hepatic oxygen delivery caused by endotoxin, result in hepatic metabolic deterioration followed by liver dysfunction and multiple organ failure. Among phosphodiesterase III inhibitors, only olprinone increases hepatosplanchnic blood flow. We evaluated the effects of olprinone on systemic hemodynamics, hepatic circulation, and hepatic oxygen delivery in a porcine model of endotoxemia. Fifteen pigs received a continuous infusion (1.7 microg. kg(-1). h(-1)) of endotoxin (lipopolysaccharide [LPS]) via the portal vein for 240 min. Seven of these pigs received olprinone infusion (0.3 microg. kg(-1). min(-1)) via a central vein from t = 150 min to t = 240 min, whereas the eight remaining pigs served as LPS controls. Continuous infusion of LPS caused significant reductions in hemodynamic variables and a significant increase in arterial lactate. After the administration of olprinone during the LPS infusion, portal venous flow and hepatic oxygen delivery were increased and were higher than in the LPS group. Furthermore, olprinone prevented any further increase in arterial lactate. We conclude that the administration of olprinone halted the disturbances in the hepatic circulation, especially in portal venous flow and hepatic oxygen delivery, in a porcine model of endotoxemia.

IMPLICATIONS

Endotoxin is a causative factor in peripheral vascular failure, resulting in a hemodynamic depression that includes a reduction in liver blood flow. The administration of olprinone (phosphodiesterase III inhibitor) improves the liver blood flow circulation in a porcine model of endotoxemia.

Effect of olprinone, a phosphodiesterase III inhibitor, on arterial wall distensibility: differentiation between aorta and common carotid artery

Although the effects of phosphodiesterase III (PDE III) inhibitors as vasorelaxants have been well documented, there are only few data on the wall response of different arteries. We evaluated the artery-specific effect of olprinone (OP), one of the PDE III inhibitors, on the major branches of human arteries and peripheral circulation. In 14 healthy subjects (average age: 57.5 +/- 21.2 years), systolic and diastolic diameters (Ds and Dd, respectively) and the time velocity integral (VI) of flow velocity patterns were measured by M-mode and Doppler echocardiography in the carotid artery (CA), the ascending aorta (asAo), the abdominal aorta (abAo), and the left ventricular outflow tract. Blood pressure (BP) was simultaneously measured using a cuff sphygmomanometer. Measurements were taken before and 20min after a bolus injection of OP (0.2 microg/kg). Distensibility (Ds - Dd), stiffness parameter beta (In(systolic BP/diastolic BP)/(Ds/Dd - 1)), cardiac output (CO: (Flow Area) x VI x HR at left ventricular outflow), selective flow volume (FV: (Flow Area) x VI x HR at CA or abAo), and vascular resistance (VR: mean BP/(CO or FV)) were then calculated. The distensibility increased significantly after OP administration (P = 0.0015), but that of the asAo or abAo did not change. Although there was a significant increase in CO (P = 0.001) and a significant decrease in systemic VR (P = 0.001) following OP administration, the FV and VR of both CA and abAo did not change significantly. The selectiveness of the effect of OP was demonstrated in terms of the CA wall distensibility. This was thought to be attributable to the differences in the structural components or the reactivity of smooth muscle cells to OP.

Site-specific effects of the nonsteroidal anti-inflammatory drug lysine clonixinate on rat brain opioid receptors

In addition to effects in the periphery through inhibition of prostaglandin synthesis, several lines of evidence suggest that nonsteroidal anti-inflammatory drugs (NSAIDs) act in the central nervous system. The possibility that the central action of NSAIDs involves regulation of opioid receptors was investigated by quantitative autoradiography of mu, delta, and kappa sites in rat brain slices. Increased (p < 0.05) labeling of mu receptors was observed in thalamic nuclei, gyrus dentate, and layers of the parietal cortex of rats treated for 10 days with lysine clonixinate. Labeling of delta receptors was lower in the lateral septum, and kappa sites decreased in thalamic nuclei. These effects were not mediated through direct interaction with opioid-binding sites, since receptor-binding assays using rat brain membranes confirmed that clonixinate up to 1 x 10(-4) mol/l does not inhibit mu, delta, and kappa receptor specific binding. Central effects of NSAIDs might, therefore, involve interaction with the opioid receptor system through indirect mechanisms.