The American journal of physiology
-
Stable isotope tracers and indirect calorimetry were used to evaluate the importance of beta-adrenergic stimulation of lipolysis and triglyceride-fatty acid cycling during fasting in healthy human volunteers. Each subject was studied after 12 and 84 h of fasting both with and without propranolol infusion (protocol 1) and when oral propranolol treatment was given throughout fasting (protocol 2). In protocol 1, the rates of appearance of glycerol and palmitic acid increased from 3.04 +/- 0.19 and 1.78 +/- 0.17 mumol.kg lean body mass-1.min-1, respectively, after 12 h of fasting to 5.28 +/- 0.31 and 3.47 +/- 0.15 mumol.kg lean body mass-1.min-1, respectively, after 84 h of fasting (P less than 0.005). ⋯ In protocol 2, the rate of lipolysis and triglyceride-fatty acid cycling was still increased by fasting despite beta-adrenergic blockade with oral propranolol. This study demonstrates that beta-adrenergic stimulation contributes to the mobilization of fat during fasting. However, other mechanism(s) can increase lipolysis and triglyceride-fatty acid cycling when beta-adrenergic receptors are continuously blocked.
-
Lidocaine and its permanently charged analogue QX-314 block sodium current (INa) in nerve, and by this mechanism, lidocaine produces local anesthesia. When administered clinically, lidocaine prevents cardiac arrhythmias. ⋯ Using a large suction pipette for voltage clamp and internal perfusion of single cardiac Purkinje cells, we demonstrate that a charged lidocaine analogue blocks INa not only when applied from the inside but also from the outside, unlike noncardiac tissue. This functional difference in heart predicts that a second local anesthetic binding site exists outside or near the outside of cardiac Na channels and emphasizes that the cardiac Na channel is different from that in nerve.
-
Hemodynamic and metabolic variables were measured for the whole body and isolated hindlimb of anesthetized dogs during resuscitation from hemorrhagic shock, using a small volume of hypertonic saline or a larger volume of hydroxyethylstarch. Twelve dogs were bled and maintained at a mean arterial pressure (MAP) of 40 mmHg for 30 min. Six dogs were then infused with 7.5% NaCl in 5 ml/kg hydroxyethylstarch (HTS group), and six received 6% hydroxyethylstarch alone (HES group) in an amount to approximate the maximum MAP achieved with hypertonic saline. ⋯ In the isolated hindlimb, vascular resistance decreased rapidly on hypertonic saline infusion but reached similar levels at 10 min of resuscitation with both fluids. With progressive lowering of blood flow to the pump-perfused hindlimb, ability of limb muscle to extract O2 was the same for the HTS and HES groups. With hemodilution by volume replacement with acellular fluid after hemorrhage, a seemingly adequate cardiac output and arterial pressure may be underresuscitation if O2 delivery does not meet the increased O2 demand.