A case of urinary incontinence by hydroxychloroquine in a geriatric patient.

WHAT IS KNOWN AND OBJECTIVE: Rheumatoid arthritis is an autoimmune disorder characterized by persistent synovitis and systemic inflammation. Genetic factors account for approximately 50% of cases of rheumatoid arthritis and environmental factors include smoking. Urinary incontinence may occur as a medication adverse effect. We present the first report of a case of hydroxychloroquine-induced urinary incontinence in rheumatoid arthritis. DETAILS OF THE CASE: A 71-year-old female with a history of rheumatoid arthritis developed urinary incontinence as an adverse drug reaction to hydroxychloroquine administered at therapeutic doses. Urinary incontinence remitted with drug withdrawal and reappeared on rechallenge. The Naranjo's algorithm indicated that hydroxychloroquine was a probable cause of this adverse drug reaction. The likely mechanism of this adverse drug is a direct action of the quinolone on the urinary system. WHAT IS NEW AND CONCLUSION: This is the first report of hydroxychloroquine-induced urinary incontinence. The absence of previous reports suggest that the drug rarely causes this adverse effect. Methotrexate is most often used as first-line treatment, and several other drugs are now available to act as Disease-Modifying Antirheumatic Drugs (DMARDs). These drugs may be used alone or combined with methotrexate, most often to increase efficacy and reduce toxicity. The introduction of new biological agents, such as abatacept, rituximab, tocilizumab and inhibitors of tumour necrosis factor, has opened new therapeutic perspectives but are restricted by high costs and risk of infections. Thus, antimalarial drugs, especially the quinolones chloroquine (CQ) and hydroxychloroquine (HCQ), are still in use, and the latter is very efficacious. An advantage of HCQ is its low toxicity compared with other antimalarial drugs. Common side-effects of HCQ and the other antimalarial drugs include gastrointestinal effects such as nausea and vomiting, as well as skin rashes and headache, whereas their most common and severe side-effect is retinopathy. No case of urinopathy has been reported previously with HCQ.

Protective role of heparin on in vitro functional aortic response in Watanabe heritable hyperlipidemic rabbits.

The effects of prolonged in vivo heparin treatment upon vasomotor responses and content of cholesterol and energy related compounds were studied in isolated thoracic and abdominal aortas from Watanabe heritable hyperlipidemic (WHHL) rabbits. Unfractionated heparin was administered subcutaneously (2 mg/kg twice a day) to 3-month-old WHHL rabbits for a period of 6 months. A group of WHHL rabbits was treated with saline solution and considered as control. Aortic cholesterol infiltration and serum cholesterol were not significantly decreased by the prolonged heparin treatment. In heparin-treated WHHL rabbits, the in vitro aortic endothelium-dependent relaxation produced by acetylcholine or calcimycin (A 23187) was greater than in saline-treated WHHL group. ATP-induced aorta relaxation (endothelium-dependent and endothelium-independent) did not vary significantly in the two groups of WHHL rabbits, even after mechanical removal of endothelium. Also the noradrenaline-induced aorta contraction did not vary between the two groups of WHHL rabbits. No significant variation in energy-related compounds (except for ADP) was found in the aortic arch. These results suggest that heparin produces a protective effect on aortic tissue by acting mainly at endothelial level.

Aortic response to relaxing agents in Watanabe heritable hyperlipidemic (WHHL) rabbits of different age.

Serum and aortic tissue cholesterol levels in parallel with aortic relaxation to endothelium-dependent and independent drugs were determined in Watanabe heritable hyperlipidemic (WHHL) rabbits in comparison with New Zealand (N.Z.) normocholesterolemic rabbits, aged 4-14 months. Serum cholesterol was elevated (626 +/- 99 mg/100 ml) in 4-6-month-old WHHL rabbits and significantly lower in 12-14-month-old animals (344 +/- 51 mg/100 ml). Cholesterol infiltration in thoracic aorta was high in young WHHL compared with N.Z. rabbits (0.88 +/- 0.3 mg/100 mg fresh tissue vs. 0.08 +/- 0.003 mg/100 mg, respectively) and it did not vary with age. In N.Z. rabbits, serum and aortic cholesterol levels were low from 4 to 14 months of age. The aortic relaxation to acetylcholine (0.03-3 microM) on EC50 noradrenaline precontracted rings was similar in 4-6-month-old WHHL and N.Z. rabbits of the same age. In WHHL rabbits, the relaxation to acetylcholine was significantly reduced in 7-11- (-35% at maximum) and in 12-14-month-old rabbits (-40% at maximum). In N.Z. rabbits the response to acetylcholine was not modified in the 3 age groups. The relaxation to ATP (30 microM to 3 mM) was reduced by age both in N.Z. and in WHHL rabbits, but in 12-14-month-old WHHL rabbits the maximal relaxing response was significantly more elevated than in age-matched N.Z. rabbits (50.1 +/- 2.5% vs. 35.1 +/- 3.2%, respectively). The aortic relaxation to NaNO2 (10 microM to 3 mM) was reduced by age both in N.Z. and in WHHL rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)

Antagonism between (-)-N6-phenylisopropyladenosine and the calcium channel facilitator Bay K 8644, on guinea-pig isolated atria.

Antagonism between (-)-N6-phenylisopropyladenosine (PIA) and the dihydropyridine calcium channel facilitator Bay K 8644 was investigated in guinea-pig spontaneously beating or electrically driven isolated atria, taken from normal and from reserpine-treated animals. PIA (3-100 nM) produced a dose-dependent decrease in contractile tension and frequency in spontaneously beating atria being more effective in reserpinized preparations. Bay K 8644 (5-200 nM) produced an increase in contractile tension in both normal and reserpinized atria. In electrically driven left atria the positive inotropic effect of Bay K 8644 was similar to that in spontaneously beating preparations. The positive chronotropic effect of Bay K 8644 was slight and variable. PIA produced a rightward parallel shift of the concentration-response curves for the positive inotropic effects of Bay K 8644 in all experimental conditions. In spontaneously beating atria from normal guinea-pigs, the Schild regression plot was linear and its slope near to unity; pA2 of PIA 8.63 +/- 0.05 (IC50 2.35 +/- 0.25 nM). In electrically driven atria the antagonism by PIA of the effects of Bay K 8644 was apparently competitive, and the IC50 of PIA was 18.6 +/- 0.4 nM. PIA antagonized the positive chronotropic effect of Bay K 8644 in spontaneously beating preparations, both from normal and from reserpine-treated animals. Carbachol did not modify the positive inotropic effects of Bay K 8644. These data indicate that PIA may interact with Bay K 8644 at the level of the slow calcium channels, and may decrease the transmembrane calcium flux into the cell.

Effect of selective agonists and antagonists on atrial adenosine receptors and their interaction with Bay K 8644 and [3H]-nitrendipine.

1. (-)-N6-phenylisopropyladenosine (R-PIA) and N6-cyclohexyladenosine (CHA), highly selective agonists at A1-adenosine receptors, 5'-N-ethyl-carboxamidoadenosine (NECA), a non-selective agonist at A1 and A2 receptors, and 2-phenylaminoadenosine (CV-1808), a selective A2 agonist, were compared in spontaneously beating and electrically driven atria. R-PIA, CHA and NECA inhibited contraction in both preparations. CV-1808 was not effective up to 500 nM. 2. 1,3-Dipropyl-8-cyclopentylxanthine (DPCPX), a new selective A1 receptor antagonist, competitively inhibited the effects of the adenosine agonists, at low concentrations (IC50 less than 1 nM). 3. CHA and NECA were able to inhibit the positive inotropic effect of Bay K 8644 both in spontaneously beating and in electrically driven atria. 4. R-PIA, CHA and NECA (agonists), 8-phenyltheophylline (PT) and DPCPX (antagonists), failed to influence [3H]-nitrendipine binding on microsomal membranes from guinea-pig atria and ventricles in a range of concentrations from 1 nM to 100 microM. 5. The data support the existence of A1 receptors in atrial tissue. No evidence for a direct interaction between adenosine analogues and Bay K 8644 was found at the level of slow calcium channels. Adenosine analogues appear to antagonize the effects of Bay K 8644 indirectly by activation of A1 receptors.

Potassium channel blockers differentially affect carbachol and (-)-N6-phenylisopropyladenosine on guinea-pig atria.

1. The effect of three different potassium channel blockers (tetraethylammonium, TEA; 4-aminopyridine, 4-AP; and apamin) and of variations in the concentration of K+ and Ca2+ in the medium, have been studied on the responses of guinea-pig isolated atria to (-)-N6-phenylisopropyladenosine (R-PIA), a stable adenosine A1-receptor agonist, and to carbachol, a muscarinic agonist. R-PIA and carbachol showed the same negative inotropic effects over a similar range of concentrations (3-300 microM), both in spontaneously beating and in electrically driven atria. 2. TEA (0.1 to 20 mM) and 4-AP (0.3 to 3 mM), both antagonized the negative inotropic and chronotropic effects of carbachol in a concentration-dependent manner. In contrast, these compounds failed to inhibit the effects induced by R-PIA. Apamin, a specific blocker of a low conductance Ca2+-activated K+ channel, was ineffective in accordance with the absence of these channels in atrial tissue. 3. TEA (0.1 to 20mM) inhibited the negative inotropic effect of carbachol, but not that of R-PIA, in atria paced and depolarized by a high K+ medium (22 mM). In this preparation Na+ current is abolished and the contraction induced by noradrenaline and electrical stimulation is solely dependent on Ca2+ influx currents. 4. Stepwise addition of Ca2+ to a calcium-depleted perfusing medium of electrically driven atria, induced a positive inotropic effect which was inhibited by R-PIA. In contrast, carbachol had no effect. 5. In agreement with our previous study, the data suggest that R-PIA acts on isolated atria by inhibiting Ca2+ influx through L-channels.

Dual effect of ATP and UTP on rat atria: which types of receptors are involved?

The effects of adenine compounds and UTP were examined in electrically driven rat left atria. ATP, ADP, AMP, adenosine and UTP caused a dual inotropic effect: first a rapid decrease in contractility, and second an increase in contractile tension. alpha,beta-Methylene ATP caused an increase in contractile tension only, whereas 2-methylthio-ATP only induced a negative inotropic effect, 1,3-Dipropyl-8-cyclopentylxanthine inhibited the negative effects of ATP and adenosine, whereas 3,7-dimethyl-1-propargylxanthine did not influence the effects of ATP. Suramin but not reactive blue 2 antagonized the positive inotropism induced by ATP and alpha,beta-methylene ATP. Suramin also abolished the positive inotropic effect induced by UTP. These results demonstrate that ATP may induce negative inotropism directly by an action on A1-adenosine receptors and positive inotropism by an action on P2x-purinoceptors. UTP induces a positive inotropic effect mediated by suramin-sensitive receptors.

Phentolamine and hypoxia: modulation of contractility and alpha 1-adrenoceptors in isolated rat atria.

The hypoxia-induced effects on the binding sites and affinity constant of adrenoceptors, in the presence and absence of phentolamine, were determined for atrial membranes of hearts from normal and genetically hyperlipidaemic Yoshida (YOS) rats. Atrial function was also measured during normoxia and hypoxia, in the presence and absence of phentolamine. Hypoxia increased alpha 1-adrenoceptor density in atrial membranes of normal rats (Bmax 10.6 to 26.7 fmoles/mg protein). Phentolamine prevented the increase in the Bmax of alpha 1-adrenoceptors and increased the equilibrium dissociation constant of these receptors (KD 0.17 to 0.53 nmol/l). Beta-adrenoceptors did not change during hypoxia, but the Bmax was slightly increased (26%) in the presence of phentolamine. Thus, the alpha 1/beta ratio increased from 0.40 in normoxia to 1.06 in hypoxia. In normoxic atria from YOS rats, the alpha 1/beta ratio was already elevated (0.86) in comparison to control rats (mainly due to a higher density of alpha 1-adrenoceptors in atrial membranes from YOS rats). This ratio was not modified by hypoxia (0.84), but decreased when phentolamine was present (0.30). Hypoxia reduced the force of contraction and increased diastolic tension of atria of normal rats, while the sinus rate was not significantly modified. Phentolamine abolished the increase in diastolic tension and reduced the negative effect of hypoxia on contractile force. In YOS rat atria, functional parameters were modified by hypoxia in a qualitatively similar way to that of normal rat atria.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacological characterization of endothelial cell nitric oxide synthase inhibitors in isolated rabbit aorta.

Different receptors mediating the release of endothelium-derived nitric oxide (EDNO) have been identified at endothelial level. In the present study we aimed to characterise, on rabbit aorta by means of pharmacological tools, the generation of EDNO by receptors located on endothelial cell membrane (M3, P2u, P2y) and by direct activation of Ca2+ entry into the endothelial cell. Four vasodilating drugs were tested (acetylcholine, UTP, A23187 and 2-methyl-thio-ATP); they were active only if the endothelial layer was intact, suggesting that they act through endothelial receptors. The effect of different nitric oxide synthase (NOS) inhibitors (0.1 mM: L- and D-NAME, L-NMMA, L-NIO and 7-NI) was investigated on NO-mediated relaxation induced by the relaxants in vessels with intact endothelium. NOS inhibitors differently affected relaxation mediated by the vasoactive drugs in isolated rabbit aorta. Reversibility of the inhibition by using a fixed concentration of L-arginine (0.1 mM) was different depending on the relaxing drug and NOS-inhibitor. The data obtained support the coexistence in aortic vessel of more than one endothelial cell NOS isoform, each provided with different receptor coupling.

P2X-purinoceptors in the heart: actions of ATP and UTP.

Positive inotropic effects of ATP and UTP (1 microM - 1mM) were studied in isolated rat and guinea pig cardiac tissues. The potency order obtained was ATP>UTP in both species, suggesting possible interaction with P2X-purinoceptors. Binding studies using [(3)H]alpha,beta-methylene ATP as marker of P2X-purinoceptors revealed two receptor sites: one high-, the other low-affinity, in atria and ventricles from rat and guinea pig. Both ATP and UTP were found to bind high-affinity sites of [(3)H]alpha,beta-methylene ATP. The effects of various calcium inhibitors such as nifedipine, dantrolene, ryanodine and TMB-8 on positive inotropic effects induced by ATP and UTP were also studied. The results suggest that ATP and UTP may increase inotropism by interaction with P2X-purinoceptors by means of a calcium-dependent mechanism.

Prolonged inhibition of nitric oxide synthesis in Yoshida hyperlipidemic rat: aorta functional and structural properties.

To test whether inhibition of nitric oxide synthesis, associated with high levels of plasmatic lipids, can induce atherosclerotic lesions and phenotypic changes in smooth muscle cell composition in the aortic wall of an atherosclerotic-resistant species such as the rat, an inbred strain of hyperlipidemic Pittsburgh Yoshida rat was subjected to prolonged treatment (2 months) with the nitric oxide-synthase inhibitor L omega-nitro-arginine-methyl ester or with L-arginine. The two types of in vivo treatments were not able to modify in vitro aortic endothelium-mediated relaxation induced by acetylcholine or calcium-ionophore A-23187, the endothelium-independent sodium nitrite relaxation and the contractile response to serotonin. Histology and lipid infiltration of vascular specimens showed that L omega-nitro-arginine-methyl ester in vivo treatment did not induce any significant change in the aortic wall. Monoclonal antibodies to myosin isoforms and immunofluorescence procedures revealed the presence of an immature smooth muscle cell subpopulation in aortic specimens from saline-treated Pittsburgh Yoshida rats, whose expansion has been related in other species to atherogenesis. This peculiar cell phenotype disappeared in our animal model after prolonged L omega-nitro-arginine-methyl ester treatment. These data indicate that, despite interference with endothelium-mediated nitric oxide synthesis, atherosclerosis does not develop in this animal model and furnish for the first time a biological justification for atherogenesis resistance of rat, i.e., the lack of activation of an immature aortic smooth muscle cell population which in atherosclerosis-prone species is involved in lesion formation.

Purine- and nucleotide-mediated relaxation of rabbit thoracic aorta: common and different sites of action.

The mechanisms of the relaxant effect of purines and pyrimidines in New Zealand rabbit isolated aorta were investigated at endothelial and smooth muscle cell levels. Endothelium-mediated relaxation by ATP was only partially inhibited by the P2-purinoceptor antagonist suramin (0.1 mM). The pyrimidine UTP produced vasodilation by acting at the endothelial level and relaxation was not antagonized by suramin (0.1 mM). This effect was not mediated by P2 purinoceptors, indicating that UTP, like ATP to a certain extent, produces relaxation via an endothelium nucleotide (N) pyrimidinoceptor. ATP, ADP, AMP, adenosine, 5'-N-ethylcarboxamidoadenosine (NECA) and inosine were all active as relaxants on smooth muscle. The NECA relaxant effect was not antagonized by P1-purinoceptor antagonists 3,7-dimethyl-1-propargylxanthine (50 microM) or 1,3-dipropyl-8-(2-amino-4-chlorophenyl)xanthine (5 microM), excluding a P1-mediated effect. P2-related activity was excluded because adenosine-mediated relaxation was not antagonized by suramin (0.1 mM). UTP was ineffective as a relaxant at smooth muscle level, thus excluding the presence of muscular nucleotide (N) pyrimidinoceptor and suggesting a P3 purinoceptor. The rank order of potency of this muscle purinoceptor was NECA > adenosine > ATP approximately equal to ADP approximately equal to AMP approximately equal to inosine.

Vasodilation and radical-scavenging activity of imperatorin and selected coumarinic and flavonoid compounds from genus Casimiroa.

Hypertension is a very widespread condition which is not strictly considered as an illness but if not countered, progressively causes damage to all tissues and loss in their functionality. For this reason the find of new antihypertensive agents is prominent and medicinal plants and their derivatives are valuable for the purpose. The genus Casimiroa (Rutaceae) includes plants from Central America and Mexico; among these, Casimiroa edulis Llave et Lex. and Casimiroa pubescens Ramirez are the most relevant species, even for their medicinal uses. The decoction of leaves and seeds is traditionally taken as a tea mainly to lower blood pressure. The object of this research was the study of vascular activity of coumarinic and flavonoid compounds isolated from seeds of Casimiroa spp. in comparison with Casimiroa edulis and Casimiroa pubescens extracts. The phenolic compounds isolated from Casimiroa were herniarin (Her), imperatorin (Imp), 8-geranyloxypsoralen (GOP) and 5,6,2',3',4'-pentamethoxyflavone (PMF). All these compounds induced vasorelaxation on rat arterial tissues although with different effectiveness. To study the cellular mechanisms of the vasorelaxation exhibited by imperatorin, we used selective inhibitors of different receptors and enzymes, such as atropine, pyrilamine, nifedipine, L-NAME and DETC. In a further step of this research, we evaluated the radical-scavenging activity of Casimiroa extracts and isolated compounds by means of DPPH assay. In general, we observed that the scavenging activities increased in a concentration-dependent manner for all substances. The phenolic compounds highlight a synergism of vasodilation and antioxidant activity which may be very useful in the management of cardiovascular diseases. Among the evaluated compounds, imperatorin shows a significant vasorelaxant activity even higher than acetylcholine and similar to nitrite, and also useful antiradical capabilities. All these properties suggest its possible role against hypertension and vasculopathies, even if in vivo studies are needed to determine the actual applications.

"Metabolic reprogramming" in ovarian cancer cells resistant to cisplatin.

The way cancer cells escape cisplatin-induced apoptosis has not been completely elucidated yet. We questioned the relevance of "metabolic reprogramming" in cisplatin-resistance by studying mitochondrial function and metabolism in human ovarian carcinoma cell lines, both cisplatin-sensitive (2008) and resistant (C13). C13 cells, in comparison to 2008 cells, showed lower apoptotic response to cisplatin exposure, lower basal oxygen consumption (4.2±0.2 vs 6.5±0.7 fmol/cell/min, p<0.005) and a lower basal transmembrane mitochondrial potential (Δψm) (18.7±1.5 vs 32.2±1 MFI p<0.001). Moreover, C13 cells showed a lower sensitivity to rotenone and oligomycin, two mitochondrial respiratory chain inhibitors. To further investigate the impact of mitochondria on cisplatin-resistance, 2008 and C13 cells were depleted of their mitochondrial DNA (rho(0)-clones). The cytotoxicity of cisplatin was lower in 2008-rho(0)clones than in 2008 cells (IC(50) of 3.56 µM and 0.72 µM, respectively) but similar between C13-rho(0) and C13 cells (IC(50) of 5.49 µM and 6.49 µM, respectively). The time-course of cell viability in glucose-free galactose medium indicated that C13 cells are more strictly dependent on glucose than 2008 cells. (1)H-NMR spectroscopy showed a higher basal content of intracellular glutathione (GSH) and mobile lipids (MLs) in C13 cells as compared to 2008 cells, with higher lipid accumulation mainly within cytoplasmic droplets of the C13 cells. These findings allow us to propose a "metabolic remodelling" of ovarian carcinoma cells to a lipogenic phenotype, which includes alteration of mitochondrial function, as an advantageous mechanism to escape cisplatin-induced apoptosis. This hypothesis is of interest to exploit new pharmacological targets to improve the clinical impact of platinum drugs.

Cell-cycle inhibition and apoptosis induced by curcumin and cisplatin or oxaliplatin in human ovarian carcinoma cells.

UNLABELLED: Alteration of appropriate cell-cycle progression and of closely related apoptotic process is a basic feature of tumour cells, and development of new tumour-targeted agents focus on apoptosis, either during cell-cycle arrest or following premature cell-cycle checkpoint exit. Increasingly, epidemiological and experimental studies suggest that curcumin protects against cancer, not only because of its well-known antioxidant properties, but also because it modulates intracellular signalling, which is related to cell proliferation and apoptosis. Cisplatin and oxaliplatin are first-line drugs in treatment of many types of epithelial cancer and their combination with other cytostatics are under investigation to limit their side effects and resistance to them. OBJECTIVES: The aim of this study was to evaluate effects of a combined treatment using curcumin with cisplatin or with oxaliplatin, in a human ovarian cancer cell line (2008) and in its cisplatin-resistant variant (C13). RESULTS: Curcumin per se caused concentration-dependent (0.1-100 microm) and time-persistent (24-72 h) reduction in cell proliferation, as well as altered cell cycle parameters and induced apoptosis, in both cell lines. When carcinoma cells were simultaneously exposed to curcumin and to cisplatin or oxaliplatin (at concentrations lower than IC(50)) cell viability was reduced more than with single-drug treatment. Moreover, dose and time related effects of curcumin, when combined with platinum drugs, were linked to consistent reduction in cell cycling and increased apoptosis, in comparison with single-drug treatment. These effects were significant both in wild type and in cisplatin-resistant cells, indicating that curcumin was also able to increase sensitivity of resistant ovarian cancer cells to cisplatin. CONCLUSIONS: The data suggests that curcumin is an interesting natural compound capable of limiting cell proliferation and possibly increasing clinical impact of platinum drugs, in ovarian cancer patients.

Activity of sap from Croton lechleri on rat vascular and gastric smooth muscles.

The effects of red sap from Croton lechleri (SdD), Euphorbiaceae, on vascular and gastric smooth muscles were investigated. SdD, from 10 to 1000 microg/ml, induced concentration-dependent vasoconstriction in rat caudal arteries, which was endothelium-independent. In arterial preparations pre-constricted by phenylephrine (0.1 microM) or KCl (30 mM), SdD also produced concentration-dependent vasoconstriction. To study the mechanisms implicated in this effect we used selective inhibitors such as prazosin (0.1 microM), an antagonist of alpha(1)-adrenoceptors, atropine (0.1 microM), an antagonist of muscarinic receptors, and ritanserin (50 nM), a 5-HT(2A) antagonist; none of these influenced vasoconstriction caused by SdD. Likewise, nifedipine (50 nM), an inhibitor of L-type calcium channels, did not modify the action of SdD. Capsaicin (100 nM), an agonist of vanilloid receptors, also did not affect vasoconstriction by SdD. We also investigated the action of SdD (10-1000 microg/ml) on rat gastric fundus; per se the sap slightly increased contractile tension. When the gastric fundus was pre-treated with SdD (100 microg/ml) the contraction induced by carbachol (1 microM) was increased, whereas that by KCl (60mM) or capsaicin (100 nM) were unchanged. The data shows that SdD increased contractile tension in a concentration-dependent way, both on vascular and gastric smooth muscles. The vasoconstriction is unrelated to alpha(1), M, 5-HT(2A) and vanilloid receptors as well as L-type calcium channels. SdD increased also contraction by carbachol on rat gastric fundus. Thus for the first time, experimental data provides evidence that sap from C. lechleri owns constricting activity on smooth muscles.

Species-dependent effects of adenosine on heart rate and atrioventricular nodal conduction. Mechanism and physiological implications.

This study 1) compares the negative chronotropic and dromotropic actions of adenosine in guinea pig, rat, and rabbit hearts; 2) investigates the mechanism(s) for the different responses; and 3) determines the physiological implications. Isolated perfused hearts were instrumented for measurement of atrial rate and atrioventricular (AV) nodal conduction time. Differences in metabolism of adenosine were determined in the absence and presence of dipyridamole (nucleoside uptake blocker) and erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA, adenosine deaminase inhibitor). Dipyridamole plus EHNA decreased adenosine's EC50 for the negative dromotropic effect by 14-fold in guinea pig heart and 1.6-fold in rat heart. This is consistent with the greater number of [3H]nitrobenzylthioinosine binding sites measured in membranes from guinea pig (1,231 +/- 68 fmol/mg protein) compared with rat (302 +/- 31 fmol/mg protein) and rabbit (260 +/- 28 fmol/mg protein) atria. The potency of adenosine to slow atrial rate and prolong AV nodal conduction time was greater in guinea pig than in rat or rabbit hearts. This rank order of potency correlated well with the number of binding sites for the specific adenosine receptor radioligand 125I-aminobenzyladenosine in guinea pig (102 +/- 13 fmol/mg protein), rat (11 +/- 0.5 fmol/mg protein), and rabbit (8 +/- 1 fmol/mg protein) atrial membranes. Hypoxia increased the rate of adenosine release by severalfold and caused slowing of heart rate and AV block. In spontaneously beating hearts, the main effect of hypoxia was a slowing of ventricular rate, which in the guinea pig heart was due to AV block and in the rat heart to atrial slowing. In atrial paced hearts, hypoxia caused a marked prolongation of AV nodal conduction time in guinea pig (39 +/- 4 msec) and rabbit (29 +/- 5 msec) hearts, but only small effect in rat hearts (10 +/- 2 msec). The differences in response to hypoxia could be accounted for by the species-dependent differences in the 1) amount of adenosine released and metabolized, 2) sensitivity of the hearts to adenosine, and 3) dependency of AV nodal conduction on atrial rate. The findings indicate that the results from physiological or pharmacological studies on adenosine in one species may not be applicable to others, and the ultimate effect of adenosine and hypoxia is to slow ventricular rate.

Resveratrol activity on guinea pig isolated trachea from normal and albumin-sensitized animals.

The relaxant effect of resveratrol on guinea pig isolated trachea (EC50 = 100 microM) was not due to interactions with histaminergic or cholinergic systems, but appeared to be influenced by beta-blockers, indomethacin and mepacrine. Antigen-induced contraction on sensitized trachea was partially antagonized by resveratrol. Resveratrol action may be partially related to arachidonic acid metabolism.

Effects of esculetin (6,7-dihydroxycoumarin) on guinea-pig tracheal chains in vitro.

Esculetin (6,7-dihydroxycoumarin) was tested in isolated guinea-pig tracheal chains from normal and ovalbumin-sensitized animals. The drug showed a concentration-dependent relaxant effect, with an EC50 of 60 microM. Pretreatment with esculetin (30-60 microM) was not able to reduce the contractile response induced by either carbachol (0.1 microM), histamine (10 microM), BaCl2 (10 mM) or K+ (80 mM). Esculetin increased the contraction evoked by PGF2 alpha and by histamine, but reduced A23187-induced contraction. Mepacrine (10 microM), a phospholipase A2 inhibitor, reduced the relaxant effect of the lower esculetin concentrations (3-60 microM). Indomethacin (0.1 microM) increased the relaxation induced by esculetin (3-10 microM). In tracheal chains from ovalbumin-sensitized guinea-pigs, esculetin (60 microM) significantly reduced the duration of the recovery phase after antigen challenge contraction. In conclusion, in our in vitro conditions, this natural coumarin derivative seems to act by interfering with the arachidonic acid cascade.