Simple and sensitive method for determination of nicotine in plasma by gas chromatography.

Smoking and other forms of nicotine consumption are among the most important risk factors for cardiovascular disease and cancer. Many of the cessation therapies require administration of nicotine. Accordingly, precision analysis for nicotine in plasma has become increasingly important. Several of the recently published methods require elaborate sample handling and/or processing. We report a simple, rapid and reliable gas chromatography method with a high sensitivity for determination of unchanged nicotine in plasma, which can be used in the processing and quantification of large series of nicotine samples, e.g., in clinical trials of nicotine-based smoking or tobacco cessation drug delivery systems.

Attenuated endothelium-dependent vascular relaxation in patients with sleep apnoea.

OBJECTIVE: To evaluate endothelium-dependent vascular function in obstructive sleep apnoea patients. DESIGN AND METHODS: Forearm blood flow and vascular resistance were studied in eight normotensives and eight obstructive sleep apnoea patients and also in eight normotensive and eight hypertensive controls after graded brachial artery infusion of acetylcholine (10-60 micrograms/min) and sodium nitroprusside (1-6 micrograms/min), respectively. Patients and controls were matched for age, sex and body weight. RESULTS: Forearm blood flow after acetylcholine infusion was reduced in patients compared with that in controls (peak flows were 6.0 +/- 0.7 and 9.8 +/- 1.5 ml/min for 100 g, respectively), but there was no difference between hypertensive and normotensive subjects. However, the hypertensive obstructive sleep apnoea group exhibited a reduced flow response to sodium nitroprusside compared with that of their corresponding hypertensive controls. Minimal forearm vascular resistance after acetylcholine infusion and after sodium nitroprusside infusion was higher in obstructive sleep apnoea patients than it was in controls. CONCLUSIONS: Endothelium-dependent vascular relaxation in patients with obstructive sleep apnoea was reduced independently of hypertension. An additional defect in endothelium-independent vascular relaxation was found in obstructive sleep apnoea patients with hypertension. These findings suggest a vascular pathogenetic link between obstructive sleep apnoea and systemic hypertension.

Smoke-derived nitric oxide and vascular prostacyclin are unable to counteract the platelet effect of increased thromboxane formation in healthy female smokers.

The incidence of cigarette smoking tends to be higher in women, justifying directed studies on smoke-related mechanisms of cardiovascular disorder in females. Platelet activity plays an important etiological role in several settings of cardiovascular disease. Cigarette smoking facilitates platelet formation of proaggregatory thromboxane A2. However, cigarette smoke contains nitric oxide (NO), which has antiplatelet activity. Furthermore, the formation of anti-aggregatory prostacyclin (PGI2) may be higher in smokers than in non-smokers. Hence, the concerted action of NO and PGI2 on platelet activity in smoking females is important to elucidate. The metabolites of TxA2, NO, and PGI2, as well as cyclic guanosine 3':5'-monophosphate (cGMP; second messenger for NO in the platelets) and cyclic adenosine 3':5'-monophosphate (cAMP; second messenger for PGI2 in the platelets), were analysed in 23 healthy female smokers (daily consumption 11-20 cigarettes per day) and in 26 matched non-smokers. The urinary excretion of 2,3-dinor TxB2 (metabolite of TxA2) was considerably higher in smokers than in non-smokers (177 vs. 72 pg/mg creatinine, respectively; P<0.001). Plasma and urinary levels of nitrate (metabolite of inhaled NO) did not differ between the groups. Plasma and urinary cGMP were slightly increased (252 vs. 193 nmol/L; P<0.05 and 0.63 vs. 0.51 micromol/24 h; P<0.05, respectively) in smokers compared to non-smokers, while platelet cGMP was lower in smokers than in non-smokers (81 vs. 10.3 pmol/10(6) platelets, respectively; P<0.05). The urinary excretion of 2,3-dinor-6-keto-PGF1a (metabolite of PGI2) did not differ between the groups. Platelet or urinary cAMP did not differ between the groups either, while plasma cAMP was lower in smokers than in non-smokers (19.2 vs. 26.2 nmol/l, respectively; P<0.001). In healthy female smokers NO is not absorbed from the inhaled smoke, and endothelial PGI2 formation is not enhanced to counterbalance the increased platelet formation of proaggregatory TxA2.

Lisinopril reduces postexercise albuminuria more effectively than atenolol in primary hypertension.

Physical exercise causes transient albuminuria. The mechanisms of postexercise albuminuria are not fully clarified but stimulation of the reninangiotensin system (RAS) probably plays a major role through intrarenal haemodynamic changes causing an elevated filtration pressure. In a randomised, double-blind, crossover study we compared the effects on urinary albumin excretion (UAE) of lisinopril (L) and atenolol (A) therapy, i.e. we aimed to investigate whether inhibition of the RAS or inhibition of beta1-adrenoceptor-mediated effects of the sympathetic nervous system differed with regard to changes in UAE. Sixteen patients with uncomplicated primary hypertension were studied. Four standardised bicycle ergometer exercise tests were performed, before and after each active treatment period. UAE 30 min postexercise, determined by radioimmunoassay, was significantly lowered by both treatments: -278 mu g center dot min-1 (L) and -199 mu g center dot min-1 (A). The reduction of postexercise UAE achieved by treatment with the angiotensin-converting enzyme (ACE) inhibitor (L) was significantly greater than that achieved by the beta1-selective adrenoceptor blocker treatment. Blood pressure (BP) at rest and during exercise were equally reduced by both drugs. In conclusion, this study showed that antihypertensive treatment with an ACE inhibitor was more effective in reducing exercise-induced albuminuria than a beta1-selective adrenoceptor-blocking agent with a similar degree of BP reduction in patients with uncomplicated primary hypertension. This suggests that the RAS plays a major role in postexercise albuminuria in hypertensive subjects. The clinical significance of this finding, however, remains to be clarified.

Platelet function and fibrinolytic activity in hypertensive and normotensive sleep apnea patients.

Platelet function and fibrinolytic activity was studied during rest and after ergometric exercise in 13 hypertensive or normotensive patients with obstructive sleep apnea (OSA) and in 10 sex- and weight-matched controls. All patients had undergone a complete polysomnography for the diagnosis of OSA. The controls did not undergo any sleep investigation but had no history of snoring or witnessed apneas during sleep. On antihypertensive drug wash-out, two of the patients were normotensive, whereas 11 had mild to moderate hypertension. Platelet aggregation measured by adenosine 5'-diphosphate- or adrenaline-induced aggregation, platelet factor-4 or beta-thromboglobulin did not differ between patients and controls. During exercise beta-thromboglobulin decreased significantly in both OSA patients and controls. Plasma tissue plasminogen activator activity was similar in OSA patients and controls and increased significantly in both groups after exercise. Plasminogen activator inhibitor type 1 (PAI-1) was 18.4 +/- 3.6 IU/ml in OSA patients compared with 8.2 +/- 1.7 IU/ml in controls (p < 0.029) during rest, indicating decreased fibrinolytic activity. The difference between groups remained after exercise (p < 0.017). Blood pressure elevation was more common and body mass index (BMI) was higher in patients with OSA, but there was no direct relation between blood pressure level or BMI and PAI-1. Nevertheless, differences between groups were smaller when blood pressure and obesity were accounted for. It is concluded that patients with OSA may exhibit decreased fibrinolytic activity. Low fibrinolytic activity may represent a confounding pathophysiological mechanism behind the high incidence of myocardial infarction and stroke in patients with OSA.

Excretion of thromboxane metabolites in healthy women after cessation of smoking.

Cigarette smokers, but not former smokers, excrete more thromboxane A2 (TxA2) metabolites in the urine than do lifelong nonsmokers, which suggests chronic activation of their platelets. To further characterize the effect elicited by smoking on platelet function, we followed the change in urinary excretion of the 2,3-dinor (Tx-M) and 11-dehydro (dTx) metabolites of TxA2, analyzed by gas chromatography/mass spectrometry and radioimmunoassay, respectively, in eight healthy women who quit habitual smoking and compared it with the recovery of these metabolites after a single dose of acetylsalicylic acid (ASA). Tx-M and dTx before cessation of smoking were approximately 550 and 600 pg/mg creatinine, respectively. Within 3 days after quitting smoking, Tx-M and dTx had dropped to stable levels of approximately 300 and 350 pg/mg, respectively. The rates of change in excretion of Tx-M and dTx after smoking cessation were more rapid (p < 0.02 and 0.02, respectively) than those observed during the recovery of platelet function after a single dose of ASA. The excretion of 2,3-dinor-6-keto-prostaglandin F1 alpha, a metabolite of prostacyclin, was not affected by smoking cessation. We conclude that cigarette smoking elicits an increase in platelet activity in the absence of vascular injury. This increase is reversible within the life span of the platelets.

Tobacco use and urinary excretion of thromboxane A2 and prostacyclin metabolites in women stratified by age.

BACKGROUND: Activated platelets have been implicated in both acute thrombus formation and atherogenesis. Because smoking is a risk factor for cardiovascular disease in men and women and male smokers have biochemical evidence of increased platelet activation, we found it of interest to study whether smoking augments platelet activity in women as well. METHODS AND RESULTS: Data on smoking habits and a urinary sample were obtained from 125 healthy female nonsmokers and an equal number of smokers, stratified by age in five groups from 18 to 59 years old. Urinary samples were analyzed with gas chromatography/mass spectrometry for the 2,3-dinormetabolites of thromboxane A2 (Tx-M), reflecting platelet activity, and prostacyclin (PGI-M), representing platelet/vessel wall interaction. Urinary Tx-M in smokers was higher than in nonsmokers (p < 0.001), increasing with the number of cigarettes smoked per day and with age. In nonsmokers, there was no difference in Tx-M between the age groups. Urinary PGI-M in smokers was higher than that in nonsmokers (p < 0.001) and decreased with age in nonsmokers but not in smokers. There was no difference in Tx-M between previous smokers and lifelong nonsmokers. CONCLUSIONS: The elevated Tx-M in women who smoke cigarettes indicates an increased platelet activity that is dependent on smoking intensity. In parallel, PGI-M is augmented, suggesting that platelet/vessel wall interaction is stimulated. Quitting smoking is an effective means to restore platelet function. We propose that the observed increase in platelet activity in women who smoke cigarettes may be related to subsequent development of cardiovascular disease and that quitting smoking should be considered a high-priority medical target also in this sex.

Cigarette smoking increases thromboxane A2 formation without affecting platelet survival in young healthy females.

Smoking is a risk factor for the development of atherosclerotic cardiovascular disease, in men as well as in women. An increased urinary excretion of the thromboxane metabolite 2,3-dinorthromboxane B2 (Tx-M) has been observed in smokers of both genders, suggesting that cigarette smoking may facilitate cardiovascular disease via an action on the platelets. The present study addressed the hypothesis that the increased Tx-M excretion in female smokers reflects a true facilitation of platelet reactivity in vivo, rather than an increased destruction of the platelets. In healthy female volunteers (aged 20-46 years, 18 smokers and 17 non-smokers) platelet life-span and indices of platelet activity were determined, together with plasma levels of plasminogen activator inhibitor-1 (PAI-1), fibrinogen, peripheral blood cell counts and hematocrit. The urinary excretion of Tx-M was higher in smokers than in non-smokers (361 vs. 204 pg/mg creatinine, respectively, p < 0.05), while plasma and urinary beta-thromboglobulin, plasma platelet factor 4, platelet mean life-span and platelet production rate did not differ between the groups. PAI-1 activity, white blood cell count and hematocrit were higher in smokers than in non-smokers (p < 0.05). These data indicate that smoking facilitates platelet formation of thromboxane A2 without affecting platelet survival; i.e. it increases the activity of platelets without affecting their viability to a measurable extent. Such an increase in platelet activity, operating in parallel to a reduced fibrinolytic activity and a higher hematocrit and white blood cell count, may play an etiological role in smoking-induced cardiovascular disease in women.

Endothelium-dependent and -independent vasodilation and reactive hyperemia in healthy smokers.

Although cigarette smoking elicits a transient increase in peripheral vascular resistance in humans, the basal blood pressure (BP) is usually slightly lower in smokers. We hypothesized that this may be due to a compensatory increase in sensitivity in smokers to endogenous vasodilators. To test this, we studied endothelium-dependent and -independent vasodilator responses, and reactive hyperemia (RH) in the forearm of 25 healthy subjects [11 smokers (S) and 14 nonsmokers (NS)]. Endothelium-dependent vasodilation was induced by infusion into a brachial artery of stepwise increasing dosages of acetylcholine (ACh, 10-60 micrograms/kg/min) and endothelium-independent vasodilation by a similar infusion of nitroprusside (N, 1-6 micrograms/kg/min). RH was induced by release of a 5-min upper arm arterial occlusion. Forearm blood flow (FBF) was recorded by plethysmography. Endothelium-dependent vasodilation was more pronounced in S than in NS (p < 0.01), the maximal FBF during infusion of ACh being 20 +/- 6 and 14 +/- 4 ml/100 ml/min, respectively. Endothelium-independent vasodilation was also larger in S than in NS (p < 0.001), the maximal FBF during infusion of N being 14 +/- 3 and 12 +/- 2 ml/100 ml/min, respectively. ACh-induced vasodilator responses in S and NS were completely blocked by atropine. They were not decreased by trimethaphan, a nicotinic receptor inhibitor. RH was slightly more pronounced in S than in NS (p < 0.02), the postocclusive FBF 15 s after release of the occlusion being 25 +/- 4 and 21 +/- 3 ml/100 ml/min, respectively We propose that cigarette smoking increases the sensitivity of the vascular smooth muscle to vasodilator stimuli.

Cigarette smoking and urinary excretion of markers for platelet/vessel wall interaction in healthy women.

1. Cigarette smoking is known to increase the risk of cardiovascular disease in both men and women. Experimental and epidemiological studies have demonstrated that cigarette smoking is associated with several indices of increased platelet activation and platelet/vessel wall interaction in men. The aim of the present study was to test the hypothesis that cigarette smoking is linked to an increased platelet activity in women also. 2. In 26 healthy smoking and non-smoking women (age 21-49 years) the urinary excretion of the thromboxane A2 metabolite 2,3-dinor-thromboxane B2 (an index of platelet activation) and of the prostacyclin metabolite 2,3-dinor-6-keto-prostaglandin F1 alpha (an index of platelet/vessel wall interaction) were analysed by g.c.-m.s. in samples collected on days 3, 10 and 20 of their respective menstrual cycles. 3. The urinary excretion of 2,3-dinor-thromboxane B2 did not vary significantly during the menstrual cycle, either in the smokers or in the non-smokers. It was consistently higher (P less than 0.004) in the group of smokers (average of day 3, 10 and 20, 395 +/- 61 pg/mg of creatinine; mean +/- SEM) than in the group of non-smokers (average 188 +/- 22 pg/mg of creatinine). 4. The urinary excretion of 2,3-dinor-6-keto-prostaglandin F1 alpha did not differ between the groups on any of the days studied (average on days 3, 10 and 20 in the smokers and non-smokers was 281 +/- 50 and 227 +/- 30 pg/mg of creatinine, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)