ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00520.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The cardiovascular actions of dopamine have been studied in the anaesthetized dog by measuring blood pressure, heart rate, cardiac output and peripheral resistance.2. Observations with phentolamine, propranolol and haloperidol indicate that dopamine acts on α‐ and β‐adrenoreceptors, and also on specific dopamine receptors.3. In dogs pretreated with phentolamine, dopamine has a potent vasodilator action which appears to be mediated through specific dopaminergic receptors.4. Displacement of noradrenaline by dopamine is not an important component of the pressor response in the dog, and dopamine does not appear to act as a partial agonist in mediating the depressor res

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00521.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Inorganic pyrophosphate (PPi) and diphosphonates inhibit glucagon‐stimulated and fluoride‐stimulated adenylate cyclase activity of rat liver.2. Concentrations of diphosphonates required to produce inhibition are lower than those of PPi, and PPi inhibited fluoride‐stimulated activity to a greater extent than glucagon‐stimulated activity.3. Diphosphonates have inhibitory activity in the presence and absence of an ATP regenerating system in the adenylate cyclase assay, and do not substantially affect the efficiency of the ATP regenerating system. No evidence was obtained that reversal of adenylate cyclase was responsible for PPi inhibition.4. Fluoride virtually completely inhibits pyrophosphatase activity in crude membrane preparations from rat liver, whereas glucagon has no detectable

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00522.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The diffusional permeabilities to24Na of collecting ducts and the ascending and descending limbs of loops of Henle were studied by microperfusion in isolated papilla of rat kidney.2. The mean permeability coefficients were 33.9 × 10−7m.s−1for descending limbs of the loop of Henle, 7.0 × 10−7m.s−1for ascending limb, and 4.0 × 10−7m.s−1for collecting ducts.3. Vasopressin did not cause any significant increase in the permeability of collecting ducts to sodium ions.4. The permeability coefficients are consistent with those required for a counter‐current system whose driving force is a sodium pump in the entire ascending limb of the loop of Henle. They suggest that solute enters the descending limb of the loop of Henle and is carried towards the tip of the papilla in the direction of fluid flow. The entry of sodium and urea into the descending limb would reduce markedly the efficiency of the proposed passive models for countercurrent multiplication and raises doubts as to the importance of such systems i

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00523.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Intravenous injections of quazodine (6,7‐dimethoxy‐4‐ethylquinazoline, 0–5 mg/kg per min) in pentobarbitone‐anaesthetized cats increased heart rate, the maximum rate of pressure development in the left ventricle (LV dP/dt max.), cardiac output and myocardial blood flow, and decreased systemic arterial blood pressure. The effects of this cardiac stimulant were examined 1, 2, and 3 h after the intravenous administration of 2 mg/kg ofE. coliendotoxin.2. During the endotoxin shock phase (>1 h after endotoxin) the most pronounced effects were decreases in systemic blood pressure and cardiac output and a severe metabolic acidosis.3. Quazodine failed to increase cardiac output during endotoxin shock and the effects on the heart rate and LV dp/dt max. were much reduced. In contrast, quazodine‐induced vasodilatation was much more marked.4. It is concluded that there is profound myocardial depression in severe endotoxin shock in the cat and that this cannot be significantly modified b

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00524.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The β‐adrenoceptor stimulants MJ9184–1 (2'‐hydroxy‐5'‐[1‐hydroxy‐2‐(2‐methyl‐1‐phenyl‐2‐propylamino)ethyl]methanesulphonanilide) and (—)‐isoprenaline have been compared for their ability to produce agonistic actions in isolated atrial and in tracheal preparations from guinea‐pigs and cats.2. The ability of the compounds to produce cardiac chronotropic actions and to reduce serotonin‐induced increases in pulmonary resistance has been assessed in anaesthetized guinea‐pigs. The findings have been compared with those obtained previously in cats.3. There are marked differences in the relative stimulant activity of the two compounds between tissues, between species and betweenin vivoandin vitrosituations.4. The results suggest that β‐adrenoceptors in cat and guinea‐pig may differ. Preparations suitable for predicting the selectivity of action of

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00525.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Treatment with allopurinol leads to increased excretion of the pyrimidine compounds orotic acid and orotidine, and to increased levels in erythrocytes of the enzymes orotate phosphoribosyltransferase and orotidylate decarboxylase.2. The effects of allopurinol on pyrimidine metabolism are enhanced by concurrent treatment with chlorothiazide.3. This interaction between allopurinol and chlorothiazide does not appear to give rise to any disadvantageous effects. Knowledge of such interactions could lead to more rational drug therapy.

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00526.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The cardiovascular effects of isoprenaline and propranolol injected through a cannula chronically implanted into a lateral cerebral ventricle were examined in unanaesthetized dogs.2. Intraventricular isoprenaline (50–200 μg) produced tachycardia and the highest dose consistently produced a fall in blood pressure. No pressor response occurred in these doses.3. Intraventricular propranolol (600 μg–2 mg) produced variable cardiovascular responses. Consistent abolition of the cardiovascular responses to intraventricular isoprenaline occurred only with a dose of 2 mg propranolol, but this dose also abolished the responses to intravenously injected isoprenaline (1–2 μg/kg).4. Pretreatment with hexamethonium (10 mg/kg, intravenously) and guanethidine (5 mg/kg, subcutaneously daily for 3 days) potentiated the cardiovascular responses to intraventricular isoprenaline. Pretreatment with atropine methonitrate (0.4 mg/kg, intravenously) reduced the depressor response to intraventricular isoprenaline but did not convert the response into a pressor one.5. The results in the unanaesthetized dog are at variance with those reported in the unanaesthetized cat in which intraventricular isoprenaline produces a pressor response, and therefore do not support the general proposition that central β‐adrenoreceptor activation leads to an elevation of blo

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00527.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Rises and falls in mean arterial (MAP) and pulse (PP) pressures from the resting value were evoked by intravenous injections of phenylephrine and glyceryl trinitrate, and were related to the reflexly evoked changes in heart period (HP; pulse interval).2. The steady‐state properties of the baroreceptor‐heart rate reflex were examined by deriving MAP‐HP curves in a group of twenty‐three healthy normotensive subjects, and in two groups of sixteen and eight subjects with essential hypertension of different severity. Each group was subdivided into two subgroups according to age: (i) 18–30 years; (ii) 33–57 years. The MAP‐HP curves are sigmoid and each is characterized by its median blood pressure (BP50), average gain (Ḡ1) and heart period range (HPR).3. In a given age group, the curves are ‘reset’ about a higher BP50with increasing severity of hypertension. There is progressive reduction in HPR (to 80–55% of normotensive HPR) due to lowering of the upper HP plateau, which probably indicates impairment of function of the vagal component of the reflex. In three out of four hypertensive groups, Ḡ is also significantly reduced to between 60 and 30% of Ḡ of normotensive subjects of the same age.4. The effect of age on the curve parameters is independent of the effects due to hypertension. For a given MAP, Ḡ and HPR are lower in old

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00528.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The effects on the coronary circulation of intravenous injections of nifedipine were compared with those of glyceryl trinitrate in conscious dogs using chronically implanted Doppler flow probes.2. Each drug causes a fall in arterial pressure and a rise in heart rate, circumflex flow and circumflex conductance.3. Dose‐response curves for peak changes in these variables are quantitatively similar for each drug (six dogs); threshold effects occur with about 0.25 μg/kg, and maximal effects with about 16 μg/kg. However, the change in circumflex conductance induced by 8 μg/kg of nifedipine last on the average of 3.5 min, whereas the effects of circumflex conductance induced by the same dose of glyceryl trinitrate last 1 min.4. The effects of 8 μg/kg of each drug were investigated in 5 dogs treated with propranolol, and propranolol plus atropine. The findings suggest that the rise in heart rate elicited by both drugs is mediated entirely through autonomic mechanisms, whereas 80% of the increase in conductance elicited by both drugs is due to their direct vasodilator action and 20% is attributable to autonomic mechanisms.5. The administration of nifedipine into the buccal cavity in doses suggested for clinical use rapidly induces a fall in arterial pressure and a rise in heart rate, coronary flow, cardiac output and cardiac work; these effects may persist for longer than 1 h.6. It is concluded that nifedipine is a potent, long acting coronary and systemic vasodilator in the unanaesthetized dog. It appears to have haemodynamic effects which resemble those of glyceryl trinitrate in some respects but not in o

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00529.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY