Heart preparation

The smallest sequence possessing most of the neurotensin spectmm of activities and its high potency is the hexapeptide C-terminus (1). [D-Trp ]-Neurotensin acts like a neurotensin antagonist in perfused heart preparations, but acts like a full agonist in guinea pig atria and rat stomach strips (122). 

FIGURE 4.15 Two pH and two K+ planar sensors in the in-situ porcine heart preparation at midmyocar-dial depth (a) and the recorded fall in the pH and increase in K+ activity, respectively, during the course of coronary artery occlusion (b). (From [18].)... 

Sugiyama, A., Kobayashi, M., Tsujimoto, G., Motomura, S., and Hashimoto, K., The first demonstration of CGRP-immunoreactive fibers in canine hearts coronary vasodilator, inotropic and chronotropic effects of CGRP in canine isolated, blood-perfused heart preparations, Jpn. J. Pharmacol, 50, 421-427, 1989. 

Abstract Recently, we have investigated Aconitum cochleare Woroschin and obtained three new alkaloids cochleareine, acoleareine from the aerial parts of the plant and cochleareinine from the roots. Cochlearenine exhibited antioxidant activity against DPPH free radical scavenging assay. The cardio active effect of has also have been studied on isolated heart preparations. 

Cochlearenine (11) was tested on isolated heart preparations and caused a dose-dependent (0.3-3.0 mg/ml) fall in heart rate, while a mild increase in the atrial force... 

Many studies have been performed in order to compare the mode of action, and retention kinetics in the myocardium, and the way of excretion of these different cationic species for both cell cultures, as well as in whole heart preparations. Even Tc NMR spectroscopy has been used to characterize in vivo the nature of the compounds for sestamibi (see Section 5.2.2.10.1). A recent comparative kinetic study between the different cations can be taken as a base for the clinical interpretation of the different perfusion imaging findings. ... 

Pharmacological manipulation of heart function can be achieved in two ways in the semi-intact heart preparation. Flies can be fed various agents in their food followed, at some later time point, by an analysis of heart function. Alternatively, it is possible to apply the chemicals via the artificial hemolymph used to bathe the heart during the image capture. This latter method permits an assessment of acute effects on heart performance and a determination of the dose dependence of the effect (Fig. 3f). 

In isolated heart preparation, acetylcholine reduces the cardiac rate and in the presence of atropine, it can stimulate the heart causing ventricular arrhythmias. 

Kinetic data for the ox heart preparation are included even though definitive data regarding homogeneity are not available. 

The results obtained in the guinea pig heart preparations are summarized in Table 7 and in Figure 9. 

Figure 2.16. The effect of change in flux through the glycolytic path (low vs high work rates) for two (A trout muscle B rat gastrocnemius) skeletal muscle systems in vivo (modified from Hochachka, 1994) and (C) for perfused rat heart preparations in vitro (modified from Kashiwaya et al., 1994). One of the instructive insights arising from these kinds of studies is the so-called [s] stability paradox remarkably stable concentrations of pathway intermediates during changes in pathway fluxes that can approach or exceed 100-fold. See text for other details.

Studies of Arrhythmogenic Effects in Isolated Heart Preparations... 

Further studies have revealed that pumiliotoxin B interacts with voltage-dependent sodium channels to elicit an increased influx of sodium ions (101,102) and, in brain and heart preparations, a stimulation of phosphoino-sitide breakdown (101,103-106). The phosphoinositide breakdown can, via inositol trisphosphate, cause release of calcium from internal storage sites. The cardiotonic activity of pumiliotoxin B and various congeners and synthetic analogs correlates well with the stimulation of phosphoinositide breakdown (104,105). A number of studies on stimulation of sodium uptake by pumiliotoxin B and inhibition by local anesthetics and other agents have appeared (106-108). The effects of pumiliotoxin B on neuromuscular preparations have been reinterpreted as due primarily to effects on sodium channels, although additional direct effects on calcium mobilization remain possible (109). It has recently been proposed that pumiliotoxin B enhances the rate of activation of sodium channels (110). One characteristic effect of pumiliotoxin B is to elicit repetitive firing in neurons, apparently because of effects on sodium channel function (109-111). 

Like LMS, SchistoFLRFamide is a potent inhibitor of visceral muscle contraction. When applied to the semi-isolated Schistocerca heart preparation, concentrations of SchistoFLRMamide between 1 nM and 0.1 nM produced an observable inhibitory effect. At 1000 nM, spontaneous heart contractions were abolished and remained so for several minutes after removal of the peptide-containing solution... 

Efforts to predict the risk of potential QT prolongation over the last decade have resulted in the number of preclinical in vitro and in vivo methodologies. In vitro methods to predict QT liabilities range from simple recombinant cellular assays to disaggregated cells, isolated tissues and perfused heart preparations." ... 

These findings are consistent with impaired fatty-acid oxidation reduced mitochondrial entry of long-chain acylcarnitine esters due to inhibition of the transport protein (carnitine palmityl transferase 1) and failure of the respiratory chain at complex II. Another previously reported abnormality of the respiratory chain in propofol-infusion syndrome is a reduction in cytochrome C oxidase activity, with reduced complex IV activity and a reduced cytochrome oxidase ratio of 0.004. Propofol can also impair the mitochondrial electron transport system in isolated heart preparations. 

Langendorff preparation An isolated heart preparation used to test drug effects on heart rate and contractile force. 

Isolated working heart preparation Perfusion of the heart ex vivo through the left atrium and ejection via the aorta resembling physiological conditions. Measurement of cardiac output. Preload and afterload can be adjusted. Other characteristics similar to Langendorff preparation. 

Stehr SN, Christ T, Rasche B et al (2007) The effects of Levosimendan on myocardial function in ropivacaine toxicity in isolated Guinea pig heart preparations. Anesth Analg 105(3) 641-647... 

Leukotrienes C4 and D4 also have very pronounced effects on the cardiovascular system. They are, for example, very effective coronary artery vasoconstrictors. A number of indirect effects have also been attributed to LTC4 and LTD4. For example, these agents effect the secretion of mucous in the respiratory tract and cause negative inotropic effects in mammalian heart preparations. Many other biological activities have been associated with the peptido-leukotrienes. 

Selaginella rupestris (L.) Spring, (aerial parts) Amentoflavone (1). Pharmaeologieal aetivity of amentoflavone on eentral nervous system, smooth museles and isolated frog heart preparations. Chakravarthy et al., 1981[412]. 

Chakravarthy, B. K. Rao, Y. V. Gambhir, S. S. Gode, K. D., Isolation of amentoflavone from Selaginella rupestris and its pharmacological activity on central nervous system, smooth muscles and isolated frog heart preparations, Planta Med, 1981, 43, 64-70. 

Contractile force is measured in an isolated arterial preparation, and heart rate is measured in an isolated heart preparation. 

In isolated rabbit heart preparations, pr-MDI and bu-MDI (3x10-5m) produced a negative inotropic action with no alteration in chronotropy (62). The negative inotropic action was sizably smaller than the increase in coronary flow produced by these agents (62). The decrease in force of contraction is beneficial for the purpose of conservation of oxygen in an ischemic heart. In-vivo studies in dogs (65) also demonstrated that the tertiary MDIs did not alter cardiac rate. 

Contractile force is measured in an Isolated. arterial preparation and heart rate Is. measured In an Isolated heart preparation. 

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