Articles: animals.
-
Plasma concentrations of atrial natriuretic peptide (ANP), plasma renin activity (PRA), plasma concentrations of aldosterone, urine flow rate and sodium and potassium excretion were studied in two groups of four conscious 3-day-old male calves, infused with hypertonic saline or vehicle. Hypertonic saline infusion (20 mmol NaCl/kg body weight) was accompanied by a progressive rise in plasma concentrations of ANP (from 16.5 +/- 0.2 pmol/l at time 0 to 29.3 +/- 3.0 pmol/l at 30 min; P less than 0.05) and by a gradual decrease in PRA (from 1.61 +/- 0.23 nmol angiotensin I/l per h at time 0 to 0.54 +/- 15 nmol angiotensin I/l per h at 90 min; P less than 0.05); there was no change in the plasma concentration of aldosterone. ⋯ During the following 22 h, urinary water and sodium excretion remained at significantly high levels. Thus, in the conscious newborn calf, changes in plasma ANP levels and urinary water and sodium excretion during hypertonic saline infusion are compatible with the hypothesis that endogenous ANP participates, at least in part, in the immediate diuretic and natriuretic renal response induced by the sodium overload.
-
Journal of anesthesia · Mar 1988
The effect of verapamil on halothane-epinephrine or digitalis-induced ventricular dysrhythmias in dogs.
The effect of verapamil on ventricular dysrhythmias was evaluated using two canine models. In one model, ventricular dysrhythmias were induced by 1% halothane-epinephrine (1.5 approximately 30 micro g/kg/min.) in 20 dogs (Group I). In the other model, ventricular dysrhythmias were induced by digoxin (0.1 approximately 0.2 mg/kg) in 27 dogs (Group II). ⋯ Lidocaine was ineffective in the remaining 4 of group I, whereas effective in the remaining 17, including those given lidocaine alone of group II. From these findings, it was inferred that Ca(2+) dependent abnormal automaticity and/or re-entry may be more closely related to the genesis of halothane-epinephrine-induced ventricular dysrhythmias refractory to lidocaine, whereas triggered activity may be more closely related to that of digitalis-induced ventricular dysrhythmias. In conclusion, verapamil was more effective against halothane-epinephrine-induced ventricular dysrhythmias than against digitalis-induced ventricular dysrhythmias.
-
The influence of acidosis on the inotropic effect of isoproterenol was studied in the isolated arterially perfused heart of the newborn rabbits. Baseline mechanical function during acidosis (pH 6.8) was not different from control (pH 7.4). However, the inotropic effect of isoproterenol was significantly suppressed in the acidotic muscles. ⋯ Adenylate cyclase activity was depressed at pH 6.8 and 6.0. These data suggest that the inotropic effect of isoproterenol is diminished in the acidotic muscle. This may be due to the decreased activation of cAMP production, which in turn most likely results from depressed adenylate cyclase activity.