Isoproterenol increases and decreases contractile force at low and high concentrations, respectively, through beta(2)-adrenoceptors overexpressed in transgenic mouse heart (TG4), consistent with activation of both G(s) and G(i) proteins. Using TG4 hearts, we demonstrated that epinephrine behaves like isoproterenol, but norepinephrine does not. Epinephrine both increased (-log EC(50)M = 9.4) and...

The turnover of norepinephrine and the enzymes responsible for the synthesis of catecholamines were studied in various organs of rats made hypertensive by DOCA and NaCl. After inhibition of tyrosine hydroxylase by a-methyl-ptyrosine, an increase in the rate of disappearance of endogenous norepinephrine in the heart, intestine, and spleen of hypertensive rats indicated an increased norepinephrin...

Limited information is available about selection of the threshold for arterial blood pressure in critically ill patients, particularly in sepsis when normal organ blood flow autoregulation may be altered. The present experimental study investigated whether increasing perfusion pressure using norepinephrine in normotensive hyperdynamic porcine bacteremia affects intestinal macro- and microcircul...

The effect of ascorbic acid on the conversion of dopamine to norepinephrine was investigated in isolated chromaffin granules from bovine adrenal medulla. Ascorbic acid was shown to double the rate of [3H]norepinephrine formation from [3H]dopamine, despite no demonstrable accumulation of ascorbic acid into chromaffin granules. The enhancement of norepinephrine biosynthesis by ascorbic acid was d...

Although hyperinsulinemia and increased adrenergic activity have been postulated to be important factors in obesity-associated hypertension, a cause and effect relation between insulin, catecholamines, and hypertension has not been established. The aim of this study was to determine whether chronic hyperinsulinemia, comparable with that found in obese hypertensive patients, causes hypertension ...

Primary cultures of bovine adrenal medullary chromaffin cells were pulse-labeled with [3H]dopamine or [3H]norepinephrine and examined for radioactive and total catecholamine contents by high performance liquid chromatography after additional incubations of 15 min to 10 days. [3H]Dopamine was rapidly taken up by chromaffin vesicles in situ and converted to norepinephrine with a half-time of appr...

AIMS Congestive heart failure is characterized by high levels of norepinephrine which is considered to be arrhythmogenic. It is unclear whether increased norepinephrine is only a marker of the severity of heart failure or whether it directly triggers ventricular arrhythmias. METHODS AND RESULTS Ventricular myocytes were isolated from eight explanted hearts of patients with end-stage heart fai...

Human plasma contains several catechols, including the catecholamines norepinephrine, epinephrine, and dopamine, their precursor, L-3,4-dihydroxyphenylalanine (L-DOPA), and their deaminated metabolites, dihydroxyphenylglycol, the main neuronal metabolite of norepinephrine, and dihydroxyphenylacetic acid, a deaminated metabolite of dopamine. Products of metabolism of catechols include 3-methoxyt...