In isolated perfused rat hearts (medium: Krebs-Ringer solution containing about 15% bovine red cells) the following parameters were estimated: heart rate (F), left intraventricular peak pressure (P), dP/dt, oxygen consumption (VO2); myocardial tissue content of glycogen, ATP, ADP, AMP, cAMP, phosphocreatin (PC) and inorganic phosphate (Pi). Isoproterenol (ISO) was administered to the non circulating system in the concentration range of 5 x 10(-10) to 5 x 10(-5) M for 4 min and 1 hour respectively by infusion into the perfusate close to the aortic canula. After administration period of 4 min dependent on the concentration of ISO, P, dP/dt, VO2 and the content of cAMP are increased. The ratios of PC/Pi and ATP/ADP as well as glycogen content are reduced. For an administration period of 1 hour at a level of 5 x 10(-9) M the effects of isoproterenol are maintained. At ISO concentration higher than 5 x 10(-9) M the effects on mechanical parameters and VO2 fall to the level of those values which are produced at 5 x 10(-9) M ISO. In contrast, high energy phosphates and glycogen content remain reduced while that of cAMP is elevated.
The majority of patients with diabetes mellitus (DM) have hypertension (HTN). A specific mechanism for the development of HTN in DM has not been described. In the Zucker, Endothel, und Salz (sugar, endothelium, and salt) study (ZEuS), indices of glucose metabolism and of volume regulation are recorded. An analysis of these parameters shows that glucose concentrations interfere with plasma osmolality and that changes in glycemic control have a significant impact on fluid status and blood pressure. The results of this study are discussed against the background of the striking similarities between the regulation of sugar and salt blood concentrations, introducing the view that DM is probably a sodium-retention disorder that leads to a state of hypervolemia.
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