Marie-Claude Auclair

Early released lipid-soluble cardiodepressant factor and elevated oestrogenic substances in human septic shock.

Abstract. A cardiodepressant factor (CDF) able to decrease contractile activity of cultured rat heart cells was determined to be located in the lipid‐soluble fraction of sera from men in septic shock. This heat‐stable CDF has a molecular weight under 1000. Repeated fractionations of sera gave evidence of an oestrone‐like chromatographic behaviour.

Interaction between parathyroid hormone and the β-adrenoceptor system in cultured rat myocardial cells

Abstract The effect of parathyroid hormone (PTH) alone and in combination with dl-sotalol, dl-propranolol, isoprenaline and calcium chloride has been investigated on cultured rat heart cells beating. PTH induced a dose-dependent positive chronotropic effect which was antagonized by sotalol non-competitively. PTH decreased the positive chronotropic effect of isoprenaline by a non-competitive antagonism. PTH reduced the negative chronotropic effect of propranolol by a competitive antagonism and the positive chronotropic effect of calcium chloride by a non-competitive antagonism. Such interactions suggest that PTH may act in vivo not entirely by stimulating a proper receptor.

Depressed isoprenaline vascular response in endotoxic rats

The injection of a sublethal dose of E. coli endotoxin (0127 B8) to intact rats (2 mg/kg i.v) or adrenalectomized rats (0.01 mg/kg i.v.) depressed hypotensive responses to isoprenaline (0.2, 0.4, 0.8 microgram/kg i.v.) for at least 4 h following endotoxin injection. These findings evidence an early (under 1 h after administration) and long-lasting (over 4 h) depression of the vascular response to isoprenaline in endotoxic rats. This depression was not related to catecholamine adrenal discharge or to the hypotensive and lethal effects of endotoxin.

Chronotropic effect of histamine on cultured neonatal rat heart cells

The positive chronotropic effect (PCE) of histamine in cultured neonatal rat heart cells was monitored using a microscopic method as well as an electro-optically recording device. The action potential frequency was also measured (by means of microelectrodes). An increase in PCE was noted when histamine (from 1 X 10(-6) M to 1 X 10(-5) M) was added to the cells. However, higher concentrations (from 1 X 10(-5) M to 1 X 10(-4) M) were less effective. The PCE of histamine was reduced by pretreating the cells with antihistaminic drugs. H1-blocking agents (promethazine and mepyramine) were more potent than H2-blocking drugs (metiamide and cimetidine). In addition, the PCE of histamine was abolished when the cells were in presence of high K+ medium (26 mEq) but contraction and action potential amplitudes were increased. Our results demonstrate that these cultures respond to histamine and that this response is abolished by antihistaminic drugs thus suggesting the H1 and/or H2 receptors may be present in the neonatal rat heart cell cultures.

Dependence on extracellular potassium of the positive inotropic response to St 587, a selective α-1 adrenoceptor agonist, in Zucker rat heart ventricle

The effects of St 587, a selective alpha-1 adrenoceptor agonist, were investigated in non obese and obese Zucker rat heart ventricles. In both groups, the numbers and affinity constants for alpha-1 adrenoceptors were found to be similar. At 4 or 10 mM [K]o, St 587 failed to increase the developed tension whereas at 14 mM [K]o, St 587 significantly increased it in both groups of rats. This effect was reversed by prazosin; St 587 also increased action potential duration at 14 mM [K]o. [K]o is thus important for the occurrence of the inotropic effect of St 587 in 12 week-old Zucker rats, either non obese or obese with reduced beta-adrenoceptor responsiveness. This suggests the participation of phosphoinositide metabolism in the mechanism of St 587 inotropic effect in the rat.