摘要:

SUMMARY1. The effects of porcine endothelin were examined in rat thoracic aortic rings.2. Endothelin was a potent contractile agonist (EC504.0 ± 0.6 nmol/L).3. Endothelin (1 nmol/L) did not affect contractile responses to cumulative concentrations of the thromboxane analogue, U46619.4. In the presence of U46619, but not phenylephrine, endothelin (1 nmol/L) and endothelium abrogated the vasodilator response to cumulative concentrations of sodium nitroprusside.5. The inhibitory effect of endothelin on vasodilator responses to nitroprusside in the presence of U46619 was abolished by nifedipine (0.1 μmol/L) but unaffected by indomethacin (3 μmol/L) or haemoglobin (10 μmol/L).6. These data suggest that endothelin generated by native endothelium exerts a physiological antagonism of sodium nitroprusside in the presence of thrombox

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01547.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. Pre‐ and postjunctional effects of endothelin (1–10 nmol/L) have been studied in the rabbit isolated ear artery and in rat isolated atria.2. Endothelin produced concentration‐dependent increases in arterial perfusion pressure, and had positive chronotropic and inotropic effects in rat atria.3. Vasoconstrictor responses of the arteries to sympathetic nerve stimulation were reduced by 1 nmol/L endothelin and abolished by 10 nmol/L endothelin. In rat atria, the chronotropic responses to nerve stimulation were markedly reduced by 10 nmol/L endothelin.4. In rabbit ear artery, vasoconstrictor responses to noradrenaline were enhanced by 1 nmol/L endothelin, but were reduced by 10 nmol/L endothelin. In rat atria, endothelin reduced the chronotropic response to isoprenaline.5. Endothelin (10 nmol/L) increased the stimulation‐induced release of radioactivity in arteries and atria labelled with [3H]‐noradrenaline by 91% and 23%, respectively.6. The p‐ and postjunctional effects of endothelin persisted in both arterial and atrial preparations for at least 30 min after

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01548.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. Synthetic human endothelin was injected intravenously over the range 1.5–50 μg to examine its cardiovascular actions in conscious sheep.2. Mean arterial pressure increased by 9–21 mmHg within 30–120s over the range 5–50 μg endothelin. The increase in blood pressure was associated with increased calculated total peripheral resistance and a fall in cardiac output and heart rate. Stroke volume was increased.3. Injection of endothelin into ganglion blocked sheep produced vasoconstriction and an increased blood pressure response associated with an attenuation of the effects on cardiac output, heart rate and stroke volume.4. This study suggests that endothelin produces potent arterial vasoconstriction and reflex mediated effects on the heart in consci

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01549.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. The radioligand [125I]‐endothelin was used to map receptors for endothelin in rat adrenal gland usingin vitroautoradiography and computerized densitometry.2. In the adrenal, a high density of binding was found in the adrenal medulla (binding affinity constant 0.18 ± 0.11 × 109M−1) and zona glomerulosa (binding affinity constant 0.18 ± 0.07 × 109M−1). Binding was low to undetectable in the zona fasciculata and zona reticularis. Unrelated peptides did not displace endothelin.3. These results provide evidence of endothelin receptor distribution in adrenal gland and suggest that endothelin might exert multiple actions in the adrenal gland on catecholamine and aldosterone biosynthesis and

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01550.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. Endothelin (Et), a vasoconstrictor peptide, was 5–10‐fold more potent (lower EC50) on isolated ring segments of large veins than on large arteries removed from dog coronary, mesenteric, femoral, renal and internal mammary vasculature and from the human internal mammary pedicle.2. In the dog large coronary artery, Et (10–30 nmol/L) caused transient relaxations partway through the generation of a concentration‐contraction curve. These relaxations were endothelium dependent.3. In conscious rabbits treated with mecamylamine, Et (0.025–0.4 nmol/kg) caused a marked rise in renal vascular resistance but hindquarter vasodilation. Under the same conditions angiotensin II constricted both beds.4. These studies suggest that Et is vascular bed and large vein selective in activity. It did not appear to be selective for large or small coronary arterie

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01551.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. The reproducibility of 24‐hour non‐invasive ambulatory blood pressure monitoring (ABPM) using the ‘Accutracker’ (AC) (Suntech Medical Instruments, NC) was determined to evaluate the AC's suitability for clinical trials investigating the effects of environmental determinants on blood pressure.2. Six healthy males from the University Department of Medicine underwent 24 h ABPM on the same working day of the week on six occasions. Reproducibility of hourly mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) was determined using analysis of variance.3. No familiarization effect of measurement with the AC was detected.4. When comparing four time periods (0000–0759 h, 0800–1259 h, 1300–1859 h and 1900–2359 h), reproducibility of SBP was highest during the afternoon (1300–1859 h) whereas reproducibility of DBP was highest during late morning (0800–1259 h).5. Hourly mean SBP was significantly lower during late morning (0800–1259 h) than in the afternoon (1300–1859 h) or at night (1900–2359 h). Hourly mean SBP and DBP was significantly lower during sleep.6. Based on a select sample of volunteers, the AC is suitable for clinical trials involving paired measurements, particularly between 0800 and 1900 h when only 10–15 subjects would provide 80% power to demonstrate a 5 mmHg difference in SBP and DBP si

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01552.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. The accuracy of blood pressure measurement with the Takeda TM‐2420 ambulatory blood pressure monitor and the TM‐2020 data recorder have been assessed by comparison with simultaneous measurements taken using auscultation and direct femoral artery measurements.2. Systolic blood pressure was underestimated by the TM‐2420 by a mean of 10 mmHg (s.d. = 6, 95% confidence interval (CI) =−13 to −7) over the range of pressures measured by auscultation. It was underestimated by 23 mmHg (s.d. = 12, 95% CI =−28 to −18) compared with direct femoral artery measurements.3. Diastolic pressure measurements were similar to those obtained by auscultation. When compared with direct femoral artery recordings, diastolic pressure was overestimated by about 5 mmHg (s.d. = 4, 95% CI = 3.4–6.6), which is consistent with indirect readings, taken with a ‘standard’ cuff (inflatable bladder 23 cm × 12 cm).4. The TM‐2420/2020 is thus suitable for ambulatory measurements of blood pressure when diastolic pressure is the

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01553.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. The present study investigated the effect of prior administration of nifedipine on AVP‐induced ACTH release in seven normal volunteers. Three protocols were used: 20 mg oral nifedipine; 0.14 pressor units intramuscular (i.m.) per kg bodyweight aqueous AVP; oral nifedipine plus i.m. AVP 90 min later. Plasma ACTH and cortisol were measured at intervals for 2.5 h during each test.2. The mean peak plasma ACTH and cortisol levels and the mean peak changes from basal in these levels were significantly lower in the nifedipine/AVP test than in the AVP alone test. The integrated area under the cortisol time curve was significantly lower for the nifedipine/AVP test than that for the AVP test alone. Nifedipine alone caused no changes in ACTH or cortisol.3. Acute administration of oral nifedipine caused an inhibition of AVP‐stimulated ACTH and cortisol release in normal humans. This effect may be due to blockade of plasma membrane calcium channels normally activated during AVP stimulation of pituitary corticotro

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01554.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. This study set out to compare the effect of the combination of fenfluramine (Fen) and naloxone (Nal) on ACTH and cortisol release with each of these agents alone in six normal volunteers. Three protocols were used: 1.5 mg/kg bodyweight oral Fen; 125 μg/kg bodyweight i.v. Nal; oral Fen plus i.v. Nal 135 min later. Plasma ACTH and cortisol were measured at intervals of 285 min over each test.2. The mean peak levels and mean peak changes from basal in plasma ACTH and cortisol were significantly greater in the combination test (Fen/Nal) than in either the Fen alone or the Nal alone tests. Fen and Nal given together cause a synergistic release of ACTH and cortisol as determined by the areas under the ACTH‐time and cortisol‐time curves for Fen/Nal compared to the sums of Fen alone plus Nal alone curves for ACTH and cortisol.3. We conclude that Fen and Nal acting synergistically work through different and potentiating mechanisms at the hypothalamic, central nervous system and/or pituitary levels to cause ACTH rel

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01555.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. In Bartter's syndrome, atrial pressures were low, consistent with volume contraction, while atrial natriuretic peptide (ANP) levels were unexpectedly elevated. Infusion of normal saline increased both right atrial pressure (RAP) and ANP levels, while administration of prostaglandin inhibitors raised RAP, probably due to volume expansion, but ANP levels fell paradoxically.2. In Gordon's syndrome, atrial pressures were unexpectedly low or normal despite volume expansion, while ANP levels were normal. Pressor infusions of angiotensin II either raised right and left atrial pressures (LAP) without increasing ANP, or increased ANP without increasing atrial pressures.3. In these two syndromes, atrial pressures and ANP levels were poorly correlated, leading to the proposal that other regulators of ANP may be important.

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01556.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY