Steady-state pharmacodynamics and pharmacokinetics of warfarin in the presence and absence of telmisartan in healthy male volunteers.

The effects of multiple-dose telmisartan on the steady-state pharmacodynamics and pharmacokinetics of warfarin were assessed in 12 healthy young males in an open-label, single-period study conducted over 30 days. Subjects received loading doses of oral once-daily warfarin on days 1 to 5, which were individually adjusted at days 6 and/or 9 to attain stable predose prothrombin time values (INRpre) of between 1.2 and 1.8 by the end of medication phase 1 (day 14). From days 15 to 24 (medication phase 2), subjects received oral once-daily telmisartan 120 mg in addition to individualized oral doses of once-daily warfarin. On days 25 to 31 (medication phase 3), oral once-daily warfarin was again administered alone at individualized doses. Under steady-state conditions, INRpre remained unchanged during medication phases 1, 2, and 3. The difference between phases 1 and 3 was -0.04 (95% confidence interval [CI]: -0.7 to 0.10) and between phases 2 and 1 was 0.03 (95% CI: -0.11 to 0.10). Mean trough plasma warfarin concentrations (Cpre) were stable during medication with warfarin alone but showed a small, although statistically significant, decrease during the combined-medication phase. The point estimate of the ratio of phase 2/phase 1 was 0.89 (95% CI: 0.84 to 0.95). The decrease in Cpre did not result in decreased anticoagulation. This suggests that the extent of pharmacokinetic interaction between telmisartan and warfarin is limited, and since telmisartan had no effect on INRpre and the concomitant medication was well tolerated, there is no evidence for a clinically relevant interaction between telmisartan and warfarin.

The effect of telmisartan on the steady-state pharmacokinetics of digoxin in healthy male volunteers.

A multiple-dose, open-label, two-period, crossover randomized study was conducted in 12 healthy male volunteers to investigate the effect of multiple-dose telmisartan on the steady-state pharmacokinetics of digoxin. On day 1 of a 7-day medication period, subjects received a loading dose of digoxin 0.5 mg in the morning, followed by an evening dose of digoxin 0.25 mg, either alone or together with telmisartan 120 mg administered in the morning. On the subsequent 6 days, either digoxin 0.25 mg or digoxin 0.25 mg together with telmisartan 120 mg was administered once daily in the morning. Each 7-day medication period was separated by a washout period of > or = 14 days. A steady-state plasma concentration-time profile was assessed for digoxin during each period and for telmisartan during the period with the combined treatment. Multiple-dose telmisartan administered with digoxin resulted in higher serum digoxin concentrations than those observed after digoxin given alone. Geometric mean AUC144-168, Cmax, and Cmin values for digoxin when given in combination with telmisartan were higher by 22%, 50%, and 13%, respectively, compared with values when given alone. However, the 90% confidence interval for the geometric mean of Cmin was within the predefined 80% to 125% range of no interaction. During combination medication, digoxin tmax was shorter and Cmax/AUC144-168 increased, suggesting that the rise in digoxin Cmax may be due to more rapid drug absorption. Study medications were well tolerated, with the incidence, nature, and intensity of adverse events being similar during both medication periods. Also, no changes in vital signs or clinical laboratory tests were observed during the study. Although there was some evidence for a pharmacokinetic interaction between digoxin and telmisartan found in this study, the safety and tolerability of digoxin were unaffected by concurrent administration of telmisartan in the study population. Since any symptoms of overdose are related only to steady state and not peak concentrations and due to the fact that there was a lack of effect on serum trough levels of digoxin in this study, it is unlikely that the findings have any clinical relevance. The magnitude of increase in digoxin concentrations is comparable with increases observed with administration of calcium antagonists, carvedilol, ACE inhibitors such as captopril, and antiarrhythmic drugs such as amiodarone, quinidine, and propafenone. Monitoring of serum digoxin concentrations should be considered when patients first receive telmisartan and in the event of any changes in telmisartan dose.

Combination of calcium channel blockers and beta-blockers for patients with exercise-induced angina pectoris: beneficial effect of calcium channel blockers largely determined by their effect on heart rate.

The combination of calcium channel blockers and beta-blockers is more effective for the treatment of exercise-induced angina pectoris than beta-blocker monotherapy. As ischemia in exercise-induced angina is essentially preceded by an increase in heart rate, calcium channel blockers with a negative chronotropic property may perform better for this purpose than nonchronotropic compounds. A 335-patient, 10-week, double-blind, parallel-group comparison of amlodipine 5 mg and 10 mg, diltiazem 200 mg and 300 mg, and mibefradil 50 mg and 100 mg treatment added to baseline beta-blocker treatment was performed. Exercise testing (ETT) was performed by bicycle ergometry. All of the calcium channels blockers significantly delayed the onset of 1 mm ST-segment depression on ETT (p < 0.001 for any treatment vs. baseline). In addition, mibefradil, in both low- and high-dose treatments, produced the largest delays (low dose: different from diltiazem and amlodipine by 24.1 and 29.8 seconds, respectively, p < 0.003 and < 0.001; high dose: different from diltiazem and amlodipine by 33.7 and 37.0 seconds, respectively, p < 0.001 and < 0.001). A stepwise logistic regression analysis revealed that this beneficial effect of calcium channel blockers was largely dependent on their effect on heart rate. Serious symptoms of dizziness likewise occurred significantly more frequently on mibefradil (p < 0.05 vs. diltiazem) and urged no fewer than 19 patients on mibefradil to withdraw from the trial. The authors conclude that calcium channel blockers with a negative chronotropic property provide a better delay of ischemia in patients with exercise-induced angina, but the concomitant risk of intolerable dizziness may reduce this benefit.

Combination of calcium channel blockers and beta blockers for patients with exercise-induced angina pectoris: a double-blind parallel-group comparison of different classes of calcium channel blockers. The Netherlands Working Group on Cardiovascular Research (WCN).

The combination of calcium channel blockers and beta blockers is more effective for the treatment of exercise-induced angina pectoris than beta blocker monotherapy. Since ischemia in exercise-induced angina is essentially preceded by an increase in heart rate, calcium channel blockers with negative chronotropic property may perform better for this purpose than nonchronotropic compounds. A 335-patient, 10-week, double-blind, parallel-group comparison of amlodipine 5 and 10 mg, diltiazem XR 200 and 300 mg, and mibefradil 50 and 100 mg treatment added to baseline beta blocker treatment was performed. Exercise testing (ETT) was performed by bicycle ergometry. Although none of the calcium channel blockers improved duration of exercise or amount of workload, all of them significantly delayed onset of 1 mm ST segment depression on ETT (p<0.001 for any treatment versus baseline). In addition, mibefradil, both low- and high-dose treatment, produced the largest delays (low dose: different from diltiazem and amlodipine by 24.1 and 29.8 s, p<0.003 and <0.001, respectively; high dose: different from diltiazem and amlodipine by 33.7 and 37.0 s, p<0.001 and <0.001, respectively). These effects were linearly correlated to the amount of rate pressure product (RPP) reduction. Serious symptoms of dizziness likewise occurred significantly more frequently with mibefradil (p<0.05) and led 19 patients taking mibefradil to withdraw from the trial. The authors conclude that calcium channel blockers with negative chronotropic property provide better delay of ischemia in patients with exercise-induced angina but that the concomitant risk of intolerable dizziness largely reduces this benefit.

Combination of calcium channel blockers and beta-adrenoceptor blockers for patients with exercise-induced angina pectoris: a double-blind parallel-group comparison of different classes of calcium channel blockers. Netherlands Working Group on Cardiovascular Research (WCN).

AIMS: The combination of calcium channel blockers and beta-adrenoceptor blockers is more effective for the treatment of exercise-induced angina pectoris than beta-adrenoceptor blocker monotherapy. As ischaemia in exercise-induced angina is preceded by increase in heart rate, calcium channel blockers with negative chronotropic properties may perform better for this purpose than nonchronotropic compounds. METHODS: A 335 patient double-blind parallel-group study comparing 14 day treatment with amlodipine 5 and 10 mg, with diltiazem 200 and 300 mg, and mibefradil 50 and 100 mg added to baseline beta-adrenoceptor blocker treatment was performed. Exercise testing (ETT) was performed by bicycle ergometry. RESULTS: Although none of the calcium channel blockers improved duration of exercise or amount of workload, all significantly delayed onset of 1 mm ST-segment depression on ETT (P<0.001 for any treatment vs baseline). In addition, mibefradil, both low and high dose treatment, produced the longest delays (low dose: different from diltiazem and amlodipine by 24.1 and 29.8 s, respectively, P<0. 003 and <0.001; high dose: different from diltiazem and amlodipine by 33.7 and 37.0 s, respectively, P<0.001 and <0.001). These effects were linearly correlated with the reduction in rate pressure product (RPP). Serious symptoms of dizziness occurred significantly more frequently on mibefradil (P<0.05), and 19 patients on mibefradil withdrew from trial. CONCLUSIONS: Calcium channel blockers with negative chronotropic properties provide greater delay of ischaemia in patients with exercise-induced angina, but the concomitant risk of intolerable dizziness attenuates this benefit.

A study comparing biopharmaceutic characteristics of four once daily controlled release diltiazem preparations.

In the present study we have compared the steady state biopharmaceutic characteristics of four diltiazem once daily controlled release capsules: Mono-Tildiem LP 300 (300 mg), Adizem XL (300 mg), Cardizem (300 mg) and Dilacor (240 mg). Sixteen healthy male volunteers (aged 22.9 +/- 3.3 years, range 19-31 years) completed an open label, multiple oral dose, randomized, four-period crossover study without a washout period in between. The volunteers received each diltiazem formulation once daily for four days. Trough diltiazem and metabolites plasma concentrations were determined on days 3 and 4. The 24-h plasma concentration-time profiles were assessed after the dose on day 4 of each period. The following steady state pharmacokinetic parameters for diltiazem were calculated: the minimum plasma concentration (cmin), the maximum plasma concentration (cmax), the time to reach that concentration (tmax), the time interval during which the plasma concentration exceeds 50% of cmax (t50), the area under the plasma concentration-time curve (AUC72-96) and the peak-to-trough fluctuation (PTF). For the metabolites of diltiazem, N-mono-desmethyl-diltiazem (NDM) and desacetyldiltiazem (DAD), AUC72-96 (AUCNDM and AUCDAD) and the ratio metabolite/parent compound were calculated. Steady state was achieved on day 3. Except one, all controlled release formulations have satisfactory controlled release properties allowing once daily administration. However, significant (P < 0.05) differences were found between the pharmacokinetic characteristics which do not allow exchange of the various formulations. Concentrations well below 50 ng.mL-1 in the morning hours were observed for Dilacor (240 mg) and Adizem XL (300 mg), which could be a disadvantage of these formulations as it is well-known that ischaemic events occur at a higher rate during that part of the day. The plasma concentration profiles NDM and DAD, the major circulating metabolites, parallel the plasma concentration profiles for the parent compound. From a clinical point of view, all treatments were well tolerated.

[The quality of life after stem cell transplantation: problems with fatigue, sexuality, finances and employment]. / Kwaliteit van leven na stamceltransplantatie: problemen met vermoeidheid, seksualiteit, financiën en werkhervatting.

OBJECTIVE: To determine the quality of life in patients after high dose chemo/radiotherapy followed by bone marrow stem cell transplantation for the treatment of a malignancy. DESIGN: Structured questionnaire and in-depth interview. SETTING: Academic Hospital Maastricht, the Netherlands. METHODS: All patients who had undergone stem cell transplantation (SCT) at least 6 months previously (n = 54) were asked to participate in an analysis of their quality of life using the 'Quality of life questionnaire' (QLQ-C30) developed by the European Organization for Research and Treatment of Cancer (EORTC) and an in-depth interview. RESULTS: The EORTC QLQ-C30 was answered by 52 (96%) of the patients and 46 (85%) participated in the interview. The patients were divided in cohorts of 6-24 (n = 16), 25-48 (n = 22) and more than 48 months (n = 14) after SCT. Quality of life was 73.9 on a 100 per cent scale. There were no significant differences between various cohorts after SCT. However, patients transplanted more than 4 years before had significantly more complaints of nausea and vomiting. The structured interview revealed significant problems with fatigue, sexuality, finances and return to work. No clear relation with time elapsed after transplantation was found. CONCLUSION: SCT has a significant impact on several quality of life issues, which should be considered in the application of this modality in palliative situations. The EORTC QLQ-C30 may be helpful to analyse overall quality of life after transplantation, but provides no information on individual effects on quality of life.

Hypertensive diabetic rats in pharmacological studies.

Since hypertensive disease and diabetes frequently occur simultaneously there exists a requirement for animal models where both pathological entities are combined. The streptozotocin (STZ)-spontaneously hypertensive rat (STZ-SHR) and the obese Zucker rat are examples of animal models where hypertension and diabetes occur simultaneously. STZ-SHRs develop a hyperglycaemic syndrome, associated with other biochemical and morphological changes that to some extent approach insulin-dependent diabetes mellitus (type 1 diabetes) combined with hypertension. The obese (Fa/?) Zucker rat is characterized by the simultaneous occurrence of obesity, hyperglycaemia, hyperinsulinaemia, hyperlipidaemia and moderate hypertension. As such it approaches the patient with non-insulin-dependent diabetes mellitus (type 2 diabetes) who is simultaneously hypertensive. Lean (fa/fa) Zucker rats are suitable controls with respect to the obese animals. Both animal models (STZ-SHRs and obese Zucker rats) were characterized with respect to their biochemical, morphometric and haemodynamic properties. Both models were examined in particular with respect to the pharmacological characteristics of their cardiovascular system, as discussed in the present survey.

Contractile responses to various stimuli in isolated resistance vessels from simultaneously hypertensive and streptozotocin-diabetic rats.

Diabetes mellitus and hypertension are common chronic diseases that frequently occur simultaneously. The induction of streptozotocin (STZ) diabetes mellitus in spontaneously hypertensive rats (SHR) offers the opportunity to investigate the influence of both entities in a reproducible manner. We investigated the effects of various vasoconstrictors on isolated small arteries from the mesenteric vascular bed of normotensive rats (Wistar-Kyoto rats, WKY) and SHR with chronic (8 weeks), STZ-induced diabetes mellitus. No consistent changes in hemodynamic parameters of the (STZ-) normotensive and (STZ-) hypertensive rats were noted. The K(+)-normalization procedure yields the individual optimal lumen diameter, which was the same for the arteries of the four groups of rats. The passive wall tension resulting from this normalization procedure was higher only in preparations from the control hypertensive group as compared with those from the control normotensive rats. Morphological investigations showed that small arteries from control SHR had an increased tunica media thickness as compared with those of control WKY; the STZ-WKY had an increased tunica media thickness as compared with preparations from control WKY. The vasoconstriction caused by alpha 1-adrenoceptor stimulation [norepinephrine (NE), methoxamine] and serotonin is unchanged in chronic experimental diabetes. The diabetic state reduced the sensitivity [-log EC50(M)] for the concentration-response curves (CRC) of calcium chloride. The CRC of potassium chloride indicated the same sensitivities, but maximal active wall tensions of vessels from STZ-SHR were reduced as compared with those from STZ-WKY. The well-known enhancement of the effects of various contractile stimuli caused by hypertension could not be demonstrated for the isolated small arteries used in the present study, although a nonsignificant tendency was observed. However, the STZ-diabetic state did not cause important additional pharmacodynamic changes, despite the morphological alterations in those vessels.

In vivo characterization of muscarinic receptor subtypes that mediate vasodilatation in patients with essential hypertension.

Attenuated cholinergic vasodilatation has been suggested as an endothelium-related mechanism involved in essential hypertension. We investigated the role of muscarinic (M) receptor subtypes in the forearm resistance vasculature. In eight white men with essential hypertension and eight matched normotensive control subjects (age of both groups, 47 +/- 4 years; mean +/- SEM), we infused the nonselective agonist methacholine in the presence of saline and the antagonists atropine (nonselective), pirenzepine (M1-selective), and AF-DX 116 (M2-selective) into the brachial artery and measured forearm blood flow and forearm vascular resistance using venous occlusion plethysmography. Affinity constants (pKb values) were determined from calculated plasma concentrations of the infused compounds and EC50 values. Sodium nitroprusside was given as an endothelium-independent control, and minimal forearm vascular resistance after 10 minutes of ischemia was used as a marker of structural vascular changes. Hypertensive patients showed higher minimal forearm vascular resistance, indicating structural vascular changes. However, sodium nitro-prusside- and methacholine-induced vasodilatation was similar in both groups, with apparent EC50 values (log moles per liter; mean +/- SEM) of -7.32 +/- 0.13 and -7.51 +/- 0.21 in hypertensive patients and -7.37 +/- 0.13 and -7.45 +/- 0.02 in control subjects, respectively. Atropine, pirenzepine, and AF-DX 116 caused a shift to the right of the concentration-response curve of methacholine, with apparent pKb values of 8.63 +/- 0.08, 6.81 +/- 0.13, and 5.51 +/- 0.29 in hypertensive individuals and 8.62 +/- 0.10, 6.98 +/- 0.08, and 5.49 +/- 0.09 in control subjects, respectively. Again, there were no statistically significant differences in these pharmacological parameters between hypertensive patients and normotensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Streptozotocin-induced diabetes mellitus in spontaneously hypertensive rats: a pathophysiological model for the combined effects of hypertension and diabetes.

The present study was undertaken to investigate the combined effects of hypertension and streptozotocin-induced diabetes mellitus in the rat. Accordingly, four groups of rats were studied: Wistar Kyoto rats (WKY), diabetic WKY, spontaneously hypertensive rats (SHR) and diabetic SHR, respectively. The mean arterial blood pressure was increased in hypertensive animals compared to normotensive animals. The base excess in the diabetic rats was higher than that of normoglycemic animals. An elevated glucose concentration was found in the blood and urine of streptozotocin-treated rats. Ketone bodies were detected in the urine and blood of the diabetic rats. Mortality rates after treatment were not different among the four groups. In separate experiments, isolated working hearts of the various groups were set up and analyzed. For the maximal left ventricular pressure (mm Hg) the following values were formed: 110.0 +/- 2.6, 93.6 +/- 2.7, 93.4 +/- 3.0, and 87.5 +/- 2.4, respectively. The wet heart weights, dry heart weights, and body weights of the diabetic rats were lower than those of normoglycemic animals. The wet heart weight/body weight ratio, however, was increased by diabetes and hypertension (0.43 +/- 0.01, 0.47 +/- 0.01, 0.47 +/- 0.01, and 0.54 +/- 0.02, respectively). There were no significant differences between the water content of the hearts from the four different groups. Pathologic examination of the hearts showed myocardial hypertrophy and medial hypertrophy of coronary arteries in diabetic and hypertensive animals. There was no difference in relative collagen content in the hearts of the four groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of aging and hypertension on the reactivity of isolated conduit and resistance vessels.

We have studied the effects of hypertension and aging on the concentration-response curves for alpha 1-adrenoceptor-mediated vasoconstriction and methacholine-induced endothelium-dependent relaxation. The experiments were performed in aortic rings and in perfused mesenteric vascular bed preparations taken from WKY rats, from SHR of 16-18, 28-30, and 58-60 weeks, and from 16- to 18-week-old SHRSP rats, respectively. The influence of aging and/or hypertension caused no alterations of the alpha 1-agonist response provoked by phenylephrine in aortic rings. Mesenteric vascular bed preparations showed an increase in maximal response to methoxamine when taken from hypertensive animals. Age per se did not change the contraction in the mesenteric arteries. Hypertension in combination with age caused a decrease in endothelium-dependent vasodilation induced by methacholine in aortic rings, but not in mesenteric arteries. However, the sensitivity to methacholine decreased age-dependently in the mesenteric vascular bed preparation taken from the WKY and SHR. The endothelium-independent relaxation induced by sodium nitroprusside showed a decrease in sensitivity in aortic rings taken from 58- to 60-week-old SHR when compared with the age-matched WKY. These findings suggest that the mechanisms beyond the endothelium involved in vasodilation are not responsible for the decreased methacholine-induced relaxation in aortic rings. It is concluded that (1) the responsiveness of resistance arteries to adrenoceptor stimulation only changes with elevated blood pressure and (2) hypertension in combination with aging induces an endothelial dysfunction in conduit arteries but not in resistance vessels.

Effects of R 56865 on postischemic ventricular function in isolated rat working heart preparations obtained from healthy, diabetic and hypertensive animals.

The present study was undertaken to evaluate the effects of R 56865 (N-[1-[4-(4-fluorophenoxy)-butyl]-4-piperidinyl)- N-methyl-2-benzothiazolamine) (Fig. 1) on postischemic ventricular function, an inhibitor of the Na+/Ca2+ overload, in the working heart preparation of the rat. The hearts were paced at 5 Hz and perfused with Tyrode solution of 37 degrees C at a physiological pH. After 15 min of pretreatment with R 56865, low-flow ischemia (30 min) was induced by reducing the perfusion pressure from 51.5 mmHg to 11.0 mmHg and R 56865 was infused simultaneously. The hemodynamic effects of R 56865 were evaluated in the concentration range [10(-8)-3.10(-6) M]. The five parameters measured were: LVP (Left Ventricular Pressure), +dP/dtmax (maximal rate of pressure increase), AO (Aortic Output), CF (Coronary Flow) and CO (Cardiac Output). They were determined in the working heart mode after 15 min of equilibration and at the end of the experiment. From these data the recovery percentages were calculated. The recovery percentages for the LVP, +dP/dtmax, AO, CF and CO for the control hearts (3.3%, 0.0%, 7.9%, 10.4% and 8.5%, respectively) differed significantly from those at 10(-7) M (39.6%, 40.8%, 25.0%, 41.8% and 29.9% respectively). The recovery percentage were the highest at 10(-6) M (79.6%, 82.1%, 54.7%, 92.7% and 67.2%, respectively). The concentration of 10(-7) M was associated with a smaller reduction in LVP (12.9%) than at 10(-6) M (25.7%).(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo characterization of vasodilating muscarinic-receptor subtypes in humans.

The role of muscarinic (M)-receptor subtypes in the regulation of vascular tone has not yet been defined in humans. To analyze the role of M-receptor subtypes in the forearm resistance vasculature of normotensive volunteers (n = 20), we infused acetylcholine (ACh) and methacholine (MCh) in the presence of saline and the antagonists atropine (nonselective), pirenzepine (M1 selective), and AF-DX 116 (M2 selective), using automated R-wave-triggered venous occlusion plethysmography. Schild analysis was applied by calculating plasma concentrations of the infused compounds and determining EC50 values. ACh and MCh both caused dose-dependent vasodilation, with EC50 values of 537 and 52 nmol/L, respectively. The apparent 10-fold higher potency of MCh compared with ACh may be explained by rapid degradation of ACh in plasma. The concentration-response curve of MCh was shifted to the right by atropine, pirenzepine, and AF-DX 116, with apparent pA2 values of 8.03 +/- 0.03, 6.71 +/- 0.08, and 5.32 +/- 0.05, respectively, and slopes not different from unity. The present technique enabled us to perform M-receptor characterization by Schild analysis in humans. The affinity constants and rank order of potency--atropine > pirenzepine > AF-DX 116-suggest that cholinergic vasodilation in this vascular bed is predominantly mediated by the M3-receptor subtype. The EC50 value of MCh and the pA2 values of pirenzepine and AF-DX 116 are comparable to values reported for in vitro experiments.

Antiischemic effects of nifedipine in isolated working heart preparations of healthy, diabetic, and hypertensive rats.

We evaluated the antiischemic effects of nifedipine in isolated working rat hearts from age-matched normotensive Wistar-Kyoto rats (WKY), diabetic WKY, spontaneously hypertensive rats (SHR), and diabetic SHR. Diabetes was induced by streptozotocin. First, we constructed concentration-response curves for the negative inotropic effect of nifedipine in every group. After 15 min of pretreatment with nifedipine (EC60), low-flow ischemia (30 min) was induced by reducing the afterload from 51.5 to 11.0 mm Hg and nifedipine was infused simultaneously. The six measured parameters were left ventricular pressure (LVP), maximum rate of pressure increase (+dP/dtmax), maximum rate of pressure decrease (-dP/dtmax), aortic output (AO), coronary flow (CF), and cardiac output (CO), determined after 15-min equilibration in the working heart mode and at the end of the experiment. From these data, the recovery percentages were calculated. There were no significant differences in sensitivity to nifedipine (as measured by the EC50 concentration) between the four groups with respect to LVP, +dP/dtmax, -dP/dtmax, CF, and CO. However, hearts from SHR were less sensitive to nifedipine than those from diabetic SHR and nondiabetic WKY with regard to AO. In isolated hearts from nondiabetic WKY and SHR, there were no significant differences between vehicle-treated organs and nifedipine-treated preparations. In hearts from diabetic WKY and diabetic SHR, however, the nifedipine-treated group (LVP 87.1 +/- 3.3 and 60.5 +/- 12.1%, respectively) recovered significantly (p < 0.05) better from ischemia as compared with the control group (LVP 35.7 +/- 14.7 and 10.7 +/- 9.8%, respectively) (n = 6 for each group).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of muscarinic receptor alkylation on endothelium-dependent vasodilation in SHR.

Possible hypertension-related alterations in the nature- and receptor reserve of the muscarinic (M) receptors mediating endothelium-dependent vasodilation remain to be elucidated. Therefore we used 4-diphenylacetoxy-N-(2-chloroethyl)-piperidine (4-DAMPmustard), an irreversible M3-receptor antagonist, to estimate the receptor reserve for the methacholine (MCh)-induced endothelium-dependent vasodilation in perfused mesenteric vascular bed preparations obtained from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) rats, respectively. The concentration-response curve parameters for the MCh-induced vasodilation were similar in both types of preparations. 4-DAMPmustard concentration-dependently decreased the maximal effect (Emax) of MCh without altering (N.S.) the pD2 in either type of preparation. The Emax was decreased to the same extent (N.S.) in both types of preparations. The dissociation constants of MCh for the response to muscarinic stimulation were comparable in preparations from SHR and WKY rats. The receptor reserve for this response, which is relatively low, does not appear to differ between vessels from SHR and WKY. It is concluded that an endothelial dysfunction does not seem to occur in perfused mesenteric resistance vessels from SHR. Also, the nature- and M-receptor reserves to not appear to differ. Therefore there are no important hypertension-related alterations in the M-receptor mediating endothelium-dependent vasodilation, at least in the experimental model used.

Characterization of the muscarinic receptors in the mesenteric vascular bed of spontaneously hypertensive rats.

OBJECTIVE: The nature of the muscarinic (M) receptor subtype mediating endothelium-dependent vasodilation was investigated in Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). DESIGN: Characterization of the muscarinic receptor mediating vasodilation and the possible hypertension-induced effects on the nature of this receptor, which have both received little attention in resistance vessels of the SHR. METHODS: After a methoxamine-induced vasoconstriction, the vessels were dilated with acetyl-beta-metacholine (MCh). The MCh-induced vasodilation was analysed by means of the M1-selective antagonist pirenzepine, the M2-selective antagonists AF-DX116 and AQ-RA 741 and the M3-selective antagonists 4-DAMP and p-FHHSiD. The potency of these compounds was quantified by means of pA2 values. Atropine, a non-selective muscarinic antagonist, was used for comparison. RESULTS: The rank order of potency for the muscarinic receptor antagonists in preparations taken from SHR and WKY rats appears to be atropine > 4-DAMP > p-FHHSiD > pirenzepine > AQ-RA 741 > AF-DX 116. This rank order corresponds to that found in isolated conduit arteries. CONCLUSIONS: The pA2 values for the various compounds were not significantly different in SHR and WKY rat preparations, indicating that the nature of this receptor is not influenced by hypertension. The high potency of the M3-selective drugs and the weak activity of pirenzepine and the M2-selective antagonists suggest a major role of M3-receptors in the cholinergic vasodilation in the perfused mesenteric vascular bed both in SHR and WKY rat preparations.