Cardiac output and its regional distribution were determined with radioactive microspheres in pentobarbitone anaesthetised rats 16 h and 5 days after sympathectomy with 6-hydroxydopamine (150 mg/kg ...i.p. over 24 h). Distribution was not different at either time in sympathectomised animals compared to controls given i.p. saline/ascorbic acid. Cardiac output was 12% greater 16 h after sympathectomy than in the controls but heart rate and blood pressure were 20% lower. Stroke volume was 43% greater in animals given 6-hydroxydopamine and total peripheral resistance 29% lower than in sham-sympathectomised rats. Five days after sympathectomy, blood pressure and heart rate were still lower in sympathectomised rats, but cardiac output and total peripheral resistance were not significantly different from control. It is concluded that basal sympathetic tone does not determine the distribution of cardiac output at rest and that its primary effect on the heart is to maintain heart rate rather than contractility.
A modular, flexible solid-phase synthetic route for the preparation of biotinylated cross-linking probes of membrane receptors is described. The route utilizes an orthogonal protection strategy ...employing a Pd0 cleavable allyl linker attached to the probe via an aspartate residue. The versatility of the method is illustrated through the synthesis of a number of arvanil-derived cannabinoid receptor ligands displaying either a photoaffinity or a chemical cross-linking group.
The distribution of cardiac output was determined by 15 micron radioactive microspheres in all the major organs of spontaneous, DOCA/NaCl and one kidney Goldblatt hypertensive rats and compared to ...normotensive Wistar rats. Although there were alterations in cardiac output distribution which were characteristic of each model of hypertension significant changes were common to all three were an increased distribution to skeletal muscle with decreases to the lungs, spleen and hepatosplanchnic tissues. The results suggest that alterations in peripheral resistance induced by hypertension are of unequal importance in the different vascular beds with certain vascular resistance changes occurring irrespective of the origin of the hypertension.
Treatment of guinea-pigs for 24 days with a single daily dose of mepyramine, 5 mg/kg i.p. had no consistent significant effect on the number of histamine H1-receptors, determined from the ...promethazine-sensitive binding of 3Hmepyramine, in cerebellum, cerebral cortex, hippocampus, hypothalamus or intestinal smooth muscle. Measurement of the time course of the block of H1-mediated blood pressure responses in conscious guinea pigs following a single i.p. injection of mepyramine, 5 mg/kg, suggested that some degree of block persisted for up to 16 h. Treatment of guinea pigs with two daily doses of 5 mg mepyramine/kg, i.p., for 10 days had no consistent effect on the KD or capacity of promethazine-sensitive 3Hmepyramine binding to cerebellum or hypothalamus.
Cardiac output and liver blood flow were measured using 15-micron diameter radioactive microspheres in anaesthetized male rats 12, 24 and 48 h and 7 days after induction of acute renal failure with ...glycerol. Plasma urea concentration was greatest in those rats studied 48 h after glycerol injection and at 7 days animals could be divided into 'recovering' and 'azotemic' on the basis of plasma urea levels. Cardiac output was significantly lower at 12 h than that found in control rats, but it was significantly greater than control values in azotemic animals at 48n h and in the 'recovering' group of rats at 7 days. Changes in cardiac output did not correlate with alterations in haematocrit. Liver blood flow showed a number of changes in the azotemic animals relative to the control rats; at 12 h it was significantly lower in the glycerol-treated rats whilst it was increased at 48 h and in both groups of animals at 7 days. When the proportion of cardiac output distributed to the liver was determined using 50-micron diameter microspheres, it was not significantly different from that determined using the smaller microspheres at 12 and 48 h after glycerol injection. This indicates that the results with the smaller microspheres were not distorted by incomplete trapping in the hepatic and splanchnic vascular beds. The implications of altered liver blood flow for drug metabolism in renal failure are discussed.
