Ventricular histamine concentrations in naive and morphine-treated rats during acute myocardial ischaemia

Release of histamine from isolated rat hearts during reperfusion is not dependent on length of ischemic insult, or contents of histamine in cardiac tissue

Release of histamine (H) by ischemia-reperfusion injury was investigated in isolated rat hearts (Langendorff model). The effect of 10, 15, 20, 25, 30, 40 and 60 min ischemia (n = 10 each) on H in the coronary effluent and in cardiac tissue was studied after 4 min reperfusion. Release of creatine kinase and lactate dehydrogenase in the coronary effluent increased with time of ischemia. Tissue H increased from 95 +/- 10 ng/g rat heart (mean +/- SEM) before ischemia to max 148 +/- 10 ng/g after 20 min ischemia (p < 0.002), and increased also after 15 (p < 0.01), 25 (p < 0.01), and 30 min (p < 0.045). H in the coronary effluent increased after 15 (from 16 +/- 3 to 26 +/- 2 pmol/min, p < 0.044), 30 (26 +/- 6 pmol/min, p < 0.027), and 60 min ischemia (47 +/- 6 pmol/min, p < 0.0044). Release of H during ischemia-reperfusion is neither dependent on the severity of the ischemic insult, nor on the level of tissue H.

Effects of suprofen on the isolated perfused rat kidney

Although suprofen has been associated with the development of acute renal failure in greater than 100 subjects, the mechanism of damage remains unclear. The direct nephrotoxic effects of a single dose of 15 mg of suprofen were compared in the recirculating isolated rat kidney perfused with cell-free buffer with or without the addition of 5 mg/dL of uric acid. There were no significant differences in renal sodium excretion, oxygen consumption, or urinary flow rates in kidneys perfused with suprofen compared with the drug-free control groups. In contrast, a significant decline in glomerular filtration rate was found after the introduction of suprofen to the kidney perfused with uric acid; no changes were found with suprofen in the absence of uric acid. A significant decrease in the baseline excretion rate of uric acid was found in rats given suprofen, compared with drug-free controls. However, the fractional excretion of uric acid was unchanged between the groups over the experimental period. In summary, suprofen causes acute declines in renal function, most likely by directly altering the intrarenal distribution of uric acid.

Ventricular histamine concentrations and mast cell counts in the rat heart during acute ischaemia

The ventricular histamine concentrations and mast cell counts of naive and disodium cromoglycate-treated rats subjected to acute left coronary artery ligation under pentobarbitone anaesthesia were examined. In naive animals, there was a significant increase in the right ventricular histamine level at 2 min following left coronary artery ligation. Left ventricular histamine concentrations tended to decrease, and were significantly lower than those of the right ventricle at 5 min. However there were no significant changes in mast cell counts of the right or left ventricles after left coronary artery ligation. Treatment with disodium cromoglycate did not significantly alter the ventricular mast cell counts, interfere with the changes in ventricular histamine concentrations, or the occurrence of early ventricular arrhythmias and haemodynamic changes in response to acute left coronary artery ligation. It is suggested that the increase in the right and decrease in the left ventricular histamine concentrations during acute myocardial ischaemia involves mainly the non-mast cell stores, instead of mast cell sources, of cardiac histamine.

Histamine attenuates the arrhythmogenic effects of norepinephrine in hearts of spontaneously hypertensive rats

A potential physiological role for cardiac histamine and its interaction with norepinephrine were investigated in isolated left ventricles from spontaneously hypertensive rats (SHR). Prior to drug administration, left ventricle-to-body weight ratios and spontaneous firing rates (beats per min) were significantly increased in SHR ventricles vs. age- and sex-matched controls (WKY). Also, action potential duration was significantly prolonged in SHR at all levels of repolarization. In all hearts, norepinephrine (10(-7)-10(-4) M) increased spontaneous rate and the percent incidence of arrhythmias. The H2-receptor antagonist cimetidine (10(-5) M) potentiated the rate and arrhythmogenic effects of norepinephrine in SHR and, to a lesser extent, in WKY preparations; propranolol (10(-6) M) reduced them. Histamine (10(-7) M) also inhibited the norepinephrine-induced increase in arrhythmias in SHR, but not in WKY. The attenuation of adrenergically induced rhythm disturbances by histamine and their potentiation by cimetidine in hypertensive hearts support the hypothesis that histamine plays a role as a postjunctional modulator of adrenoceptor function in a setting of hypertension and myocardial hypertrophy.

Plasma, cardiac tissue and brain morphine concentrations in acute and chronic morphine-treated rats

1. The plasma, cardiac tissues and brain morphine concentrations in rats after acute or chronic morphine treatment were measured by high-performance liquid chromatography. 2. Morphine concentrations in plasma and cardiac tissues were found to be significantly higher than those in brain after acute morphine injection. However, after chronic oral administration, morphine concentrations in plasma, cardiac tissues and brain were similar. 3. Brain concentrations of morphine following chronic administration were higher than those obtained after acute administration although concentrations in plasma and cardiac tissues were lower.