| 1. |
- Hellstrand, Per, et al.
(author)
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O2 consumption, aerobic glycolysis and tissue phosphagen content during activation of the Na+/K+ pump in rat portal vein
- 1984
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In: Pflügers Archiv. - 0031-6768. ; 401:2, s. 119-124
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Journal article (peer-reviewed)abstract
- Oxygen consumption, lactate production and tissue contents of ATP, phosphocreatine (PCr) and lactate were measured following readdition of K+ to K+-depleted rat portal veins, in order to study the energy turnover associated with Na+/K+ pumping. During incubation in K+-free medium at 37 degrees C spontaneous contractions disappeared in 10-20 min. Readdition of K+ (5.9 mM) after 40 min K+-free incubation caused hyperpolarization of the cell membrane for the first 5-10 min and then gradual depolarization with return of spontaneous action potentials and contractions by 10-20 min. During the first 4-6 min after K+ readdition aerobic lactate production was about doubled and then gradually returned to the original level (0.17 mumol/min g) at about 20 min. The increase in glycolytic rate was prevented by 1 mM ouabain. In contrast, O2 consumption (in K+-free medium, 0.38 mumol/min g) rose by about 10% when K+ was added and this increase lasted about 5 min. By 8 min after K+ addition the increased glycolysis and oxidative phosphorylation had accounted for each about the same amount of extra ATP generation over that extrapolated from the steady rate before K+ addition. The average total increase in ATP turnover in the first 8 min was 15%. During this period there was no change in the cellular content of ATP, PCr, or extractable ADP. The results indicate that Na+/K+ pumping utilizes a relatively small share of the total energy turnover in the vascular smooth muscle but is to a large extent dependent on aerobic glycolysis and therefore a major site of carbohydrate usage.
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| 2. |
- Wennergren, Göran, 1947, et al.
(author)
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Cardiovascular effects elicited from the ventral surface of medulla oblongata in the cat.
- 1980
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In: Pflugers Archiv : European journal of physiology. - 0031-6768. ; 387:2, s. 189-95
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Journal article (peer-reviewed)abstract
- Cardiovascular adjustments induced by topical application of drugs on a restricted area on the ventral surface of the medulla oblongata, corresponding to the caudal part of the rostral chemoreceptor area and the intermediate area, have been studied in chloralose-anesthetized cats. Topical application of GABA or glycine on these structures resulted in blood pressure fall, bradycardia, vasodilatation in the kidney and the skeletal muscles and also depression of respiration. Similar responses except for a slight tachycardia occurred with application of physostigmine. Application of GABA resulted in a marked attenuation of the reflex vasoconstrictor responses to removal of arterial baroreceptor restraint (carotid occlusion), particularly in the kidney, and to disappearance of the reflex renal vasodilatation to baroreceptor stimulation. The findings suggest that GABA application leads to a general diminution of the tonic vasomotor neuron activity, and with regard to renal vasomotor neurons a virtual cessation. Atropine methylnitrate application induced blood pressure rise, increased peripheral resistance in both skeletal muscle and kidney and a strongly potentiated renal vasoconstrictor response to carotid occlusion. The results indicate that the studied superficial medullary structures play an important role for the maintenance of tonic vasomotor neuron activity, especially renal.
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