Isolated Rat Papillary Muscles Research Articles

Effect of Angiographic Contrast Agents on the Mechanical Performance of the Isolated Rat Papillary Muscle Preparations

The effects of the radiographic contrast agents Renografin, Isopaque, and Hypaque on the mechanical performance of isometrically contracting rat papillary muscle was compared to a new contrast agent, Amipaque. It was found that exposure to Amipaque resulted in significantly less depression of contractile activity than any of the other agents. Changes in mechanical performance associated with exposure to Renografin, Isopaque, or Hypaque could not be attributed to either hypocalcemia or hypoxia. The decrease in developed tension and increase in resting tension was similar to that produced by Krebs-Henseleit containing hypertonic (1420 mmol) glucose or sucrose. Thus, the data support the concept that hyperosmolarity of the radiographic contrast agents may be primarily responsible for the adverse effects on mechanical performance of the myocardium associated with angiography.

Myocardial stiffness during hypoxic and reoxygenation contracture.

Isolated rat papillary muscle preparations were used to study hypoxic contracture, and cat papillary muscle preparations with ouabain to study reoxygenation contracture. Electronic analysis of the response to rapid small sinusoidal perturbations gave a continuous measurement of the elastic and viscous components of total stiffness. Increased resting force during hypoxic contracture was characterised by an increase in resting elastic and viscous stiffness relative to the control stiffness-active force relationships. During reoxygenation contracture the stiffness-force relationships followed those of active force development. The linear active force-elastic stiffness relationship (dt/dl=kT+c) was also reversibly altered during hypoxic contracture, predominantly by an increase in intercept c. These data imply that hypoxic contracture unlike reoxygenation contracture is not due solely to a rise in intracellular calcium, but is associated with a component of stiffness not participating an active force development, for example rigor.

The postnatal development of adrenoceptor responses in isolated papillary muscles from rat

The postnatal development of positive inotropic responses in ventricular tissue was investigated using isolated rat papillary muscles. Responses to exogenous noradrenaline or isoprenaline were already fully developed in preparations from newborn rats. These newborn preparations were also supersensitive to noradrenaline. Responses to field stimulation of intramural nerves or to tyramine were very low in preparations from animals of up to two weeks in age, but had increased to near adult values by 3 weeks of age. This increase in responsiveness was correlated with a progressive increase in sympathetic innervation revealed by fluorescence histochemistry. It is concluded that beta-receptors are present on the ventricular myocardium at birth in the rat, but that positive inotropic responses to sympathetic nerve stimulation do not develop until between 2 and 3 weeks of age.

Mechanical and structural correlates of contracture induced by metabolic blockade in cardiac muscle from the rat.

We performed morphological studies of myocardial contracture to define its nature and relationship to mechanical changes occurring during metabolic blockade. Isolated rat papillary and trabecular muscles were stretched to the apices of their length-tension curves and stimulated to contract isometrically 12 times a minute at a temperature of 28 degrees C. Incomplete and total metabolic blockade were induced by 1 hour of hypoxia (95% N2, 5% CO2) or by hypoxia plus glycolytic blockade with iodoacetic acid, 10-4M, respectively. In oxygenated control preparations, mechanical performance was stable for the 60-minute experimental period. In preparations exposed to hypoxia, developed tension fell to 7 +/- 2% of prehypoxia values at 60 minutes. Contracture tension increased progressively to 2.5 +/- 0.4 g/mm2. With total metabolic blockade, developed tension declined to zero by 10 minutes, contracture tension rose to an average peak value of 5.3 +/- 0.4 g/mm2 by 15 minutes, and subsequently slowly declined. All preparations were fixed at Lmax in the muscle bath. Light and electron microscopic studies revealed focal irregularities of A, I, and Z bands with sarcomere malalignment, hypercontraction, and fiber disruption, which increased in severity with increasing metabolic blockade. Linear densities appeared in mitochondria following total metabolic blockade, but mitochondria appeared normal otherwise. Thus, myocardial contracture after metabolic blockade is a focal process beginning within the sarcomere; morphological alterations in the contractile apparatus correlate with mechanical changes and are more severe than those in the mitochondria.

Myocardial relaxation. I. Effect of nitroprusside on the tension prolongation phenomenon.

The effects of nitroprusside and cyanide on myocardial relaxation were studied during hypoxia and reoxygenation of isolated rat papillary muscle, and during segmental ischemia and reperfusion in the intact dog heart. Nitroprusside did not affect isolated muscle performance before or during hypoxia. During reoxygenation of hypoxic muscles, the tension prolongation phenomenon (which characterizes abnormal or prolonged relaxation) was only slightly attenuated by the addition of nitroprusside to the muscle bath; in contrast, cyanide (at concentrations that did not prevent the return of tension) abolished tension prolongation during reoxygenation. During reperfusion of ischemic segments in intact hearts, the prolongation of segment tension was not affected by systemic administration of nitroprusside, but was abolished by intracoronary cyanide. Attenuation of the tension prolongation phenomenon by nitroprusside in the isolated muscle may be due to the liberation of cyanide. Inasmuch as nitroprusside did not affect the tension prolongation phenomenon in the intact heart, it is unlikely that the influence of this drug on left ventricular diastolic compliance is mediated through an alteration in the tension prolongation phenomenon.

Effects of acetaldehyde upon mechanical properties of isolated rat papillary muscle: T. Sakurai, W.H. Abelmann, Beth Israel Hospital and Harvard Medical School, Boston, MA., U.S.A.

Effects of acetaldehyde upon mechanical properties of isolated rat papillary muscle: T. Sakurai, W.H. Abelmann, Beth Israel Hospital and Harvard Medical School, Boston, MA., U.S.A.

摘出並びに生体臓器のCyclic Nucleotides測定のためのMicrowave照射装置;ラット摘出乳頭筋およびマウス脳内のCyclic AMPとCyclic GMP量

A microwave apparatus applied for radiation on the animal tissue in vitro as well as in vivo was designed and produced by us in cooperation with NEC Co. The temperature of Locke's solution in an organ bath of 5 ml and that of the mouse brain set in the microwave apparatus increased linearily with increasing the microwave intensity and irradiation time. When the Locke's solution and the mouse brain was irradiated by the microwave having an intensity of 2.0 kw for 2.0 sec, their temperatures increased up to about 90°C.Levels of cyclic AMP and cyclic GMP in the isolated rat papillary muscle, kept in Locke's solution and irradiated by the microwave (2.0kw) for 2.0 sec, were 4.075 and 2.098 pmol/mgprotein, respectively. When the papillary muscle was treated with aceton dry ice instead of the microwave radiation, those levels were 5.870 and 1.382pmol/mgprotein, respectively. Between the levels of cyclic AMP or cyclic GMP in the papillary muscles treated with microwave irradiation and those treated with aceton dry ice, there was no significant difference. When the rat papillary muscle driven by electrical stimulation in a frequency of 2 Hz for 30 min and irradiated by microwave (2.0kw) for 2.0 sec, levels of cyclic AMP and cyclic GMP in the muscle were 4.178and 0.310 pmol/mg-protein, respectivley.Levels of cyclic AMP and cyclic GMP in the brain of mouse irradiatedby microwave (2.0kw) for 2.0 sec were 6.494 and 0.772 pmol/mg. protein, respectively.

Strength-interval curves of isolated rat papillary muscle during hypoxia and reoxygenation: Effect of lidocaine

Strength-interval curves (SIC) were evaluated using computerized techniques each minute during five minutes of hypoxia and ten minutes of reoxygenation in ten isolated muscle preparations paced at 50 beats/minute. The falling limb of the SIC was measured at six 15 msec intervals during repolarization. At five minutes of hypoxia, the SIC was shifted to the left, indicating marked shortening of refractoriness (p<0.001). Following one minute of reoxygenation, the SIC approached control values; at 2–3 minutes of reoxygenation, the SIC reversed its movement from the one observed at one minute of reoxygenation and moved sharply to the left with refractoriness significantly shorter than five minutes of hypoxia (p<0.001). Recovery occurred at 6–10 minutes of reoxygenation. Eight muscles were exposed to 1, 5, 10, and 20 μg/ml of lidocaine. The control SIC at each concentration of lidocaine was shifted upward and to the right, indicting prolonged refractoriness and increasing diastolic threshold. During hypoxia, 1 μg/ml had little affect on the SIC. Five μg/ml reduced the SIC shift to the left while 10–20 μg/ml reversed the SIC shift from leftward to rightward, thus increasing refractoriness and diastolic threshold of the hypoxic muscle. Lidocaine only modified the reoxygenation phase without abolishing the supernormal refractory period phase. It is concluded that: 1) shifts in the SIC of isolated heart muscle during hypoxia and reoxygenation are similar to those previously reported in the intact dog heart; 2) in concentrations of 5 μg/ml or greater, lidocaine displaces the SIC during hypoxia upward and to the right; and 3) electrical instability during reoxygenation is characterized by oscillatory shifts in the SIC which are not abolished by lidocaine.

131) - Negative inotropic effect of noradrenaline on isolated rat papillary muscle and change in cyclic nucleotide levels

131) - Negative inotropic effect of noradrenaline on isolated rat papillary muscle and change in cyclic nucleotide levels

Myocardial sarcomere dynamics during isometric contraction.

1. Sarcomere lengths were measured during rest and throughout the time course of isometric contractions in thin, isolated rat papillary muscles using light diffraction techniques. 2. Shortening of the sarcomere length occurred upon contraction at all muscle lengths, averaging 7% at optimal length and more at shorter lengths. Relative to the narrow range of sarcomere lengths spanning the length--tension curve, this degree of shortening was considerable. 3. Local changes of sarcomere length were quantitatively paralleled by local changes of tissue segment length, the latter demarcated by microspheres lodged within the muscle tissue. At all but the shortest muscle lengths, sarcomere shortening was fully accounted for by equivalent lengthening of the non-striated regions near the clamped ends of the preparation. 4. It seems likely that these regions near the clamped ends of the preparation. 4. It seems constitute the source of the large series elasticity characteristic of isolated papillary muscle preparations such as this.

Interval dependent inotropic effects in the rat myocardium and the effect of calcium.

Peak isometric tension was measured in isolated rat papillary muscles at different external calcium levels. Rested state contraction (RSC) tension follows a sigmoid curve when plotted against external calcium concentration [Ca]0. Half maximum tension is given at [Ca]0=0.4 mM. Tension declines with increasing stimulation frequency at [Ca]0=2.5 mM. As [Ca]0 is lowered a positive inotropic response to increasing frequency develops over the range of 20–100/min. Similarly post stimulus potentiation can only be elicited at low [Ca]0 levels. The interactions of [Ca]0 and the inotropic effects of stimulation suggest the presence of a pool of releasable Ca, which can be filled passively at high external calcium levels. When [Ca]0 is lower than about 1.5 mM filling becomes stimulus dependent. The identity of phase-plane plots of contraction cycles following potentiation at low [Ca]0 with those of RSC contractions at higher [Ca]0 levels supports the idea that potentiation at low calcium levels operates by the same mechanism as increasing [Ca]0. The rat myocardium has similar properties to that of other species with respect to inotropic effects of stimulation only when the external calcium is reduced to low levels (0.2–0.4 mM).

Influence of corticosteroids on mechanical performance of isolated rat papillary muscles.

ARTICLESInfluence of corticosteroids on mechanical performance of isolated rat papillary musclesAM LeferAM LeferPublished Online:01 Mar 1968https://doi.org/10.1152/ajplegacy.1968.214.3.518MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByCardiac Hypertrophy and Related Dysfunctions in Cushing Syndrome Patients—Literature Review28 November 2022 | Journal of Clinical Medicine, Vol. 11, No. 23New insights into the roles of glucocorticoid signaling dysregulation in pathological cardiac hypertrophy28 August 2021 | Heart Failure Reviews, Vol. 27, No. 4Ventricular systolic dysfunction in dogs diagnosed with hypoadrenocorticismJournal of Veterinary Cardiology, Vol. 41NADPH oxidases and HIF1 promote cardiac dysfunction and pulmonary hypertension in response to glucocorticoid excessRedox Biology, Vol. 34Reversible Biventricular Heart Failure Due to Primary Adrenal InsufficiencyJACC: Case Reports, Vol. 2, No. 3Electrocardiogram Changes in Addison Disease: Potential Clinical Marker for Adrenal CrisisAACE Clinical Case Reports, Vol. 5, No. 5Hypothalamic-Pituitary-Adrenal Axis Modulation of Glucocorticoids in the Cardiovascular System16 October 2017 | International Journal of Molecular Sciences, Vol. 18, No. 10Getting to the heart of intracellular glucocorticoid regeneration: 11β-HSD1 in the myocardiumJournal of Molecular Endocrinology, Vol. 58, No. 1Corticosteroids Are Essential for Maintaining Cardiovascular Function in Male Mice24 May 2016 | Endocrinology, Vol. 157, No. 7Glucocorticoid signaling in the heart: A cardiomyocyte perspectiveThe Journal of Steroid Biochemistry and Molecular Biology, Vol. 153Impact of vitamin D3 on cardiovascular responses to glucocorticoid excess19 September 2012 | Journal of Physiology and Biochemistry, Vol. 69, No. 2Cardiac Function in Congenital Adrenal Hyperplasia: A Pattern of Reversible CardiomyopathyThe Journal of Pediatrics, Vol. 162, No. 6Non-genomic effect of glucocorticoids on cardiovascular system23 September 2012 | Pflügers Archiv - European Journal of Physiology, Vol. 464, No. 6Glucocorticoid signaling in cardiac diseaseHormone Molecular Biology and Clinical Investigation, Vol. 4, No. 2Ligand-based gene expression profiling reveals novel roles of glucocorticoid receptor in cardiac metabolismNoritada Yoshikawa*, Masao Nagasaki*, Motoaki Sano, Satori Tokudome, Kazuko Ueno, Noriaki Shimizu, Seiya Imoto, Satoru Miyano, Makoto Suematsu, Keiichi Fukuda, Chikao Morimoto, and Hirotoshi Tanaka1 June 2009 | American Journal of Physiology-Endocrinology and Metabolism, Vol. 296, No. 6Therapeutic manipulation of glucocorticoid metabolism in cardiovascular disease26 March 2009 | British Journal of Pharmacology, Vol. 156, No. 5Conditional glucocorticoid receptor expression in the heart induces atrio‐ventricular block21 May 2007 | The FASEB Journal, Vol. 21, No. 12Molecular Mechanisms of Impaired Urinary Concentrating Ability in Glucocorticoid-Deficient Rats17 August 2005 | Journal of the American Society of Nephrology, Vol. 16, No. 10Reversible Cardiomyopathy Caused by an Uncommon Form of Congenital Adrenal Hyperplasia12 May 2004 | Pediatric Cardiology, Vol. 25, No. 6Glucocorticoid modulation of protein phosphorylation and sarcoplasmic reticulum function in rat myocardiumM. 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Mechanical activity of rat papillary muscle

Isometric contractions of isolated rat papillary muscles driven at a constant rate have been recorded from paired muscles from hearts of rats 2–6 months of age. At 37°C and a rate of 30/min. tension reaches maximum in 30–60 minutes and then declines slowly during the succeeding 4–12 hours. The maximum tension and the rate of decline with time are related to the diameter of the muscle; however, it has not been possible to demonstrate a definite limit to diameter below which the contraction of the muscle is independent of variations in size. Most factors which increase the force of contraction do not prevent the slow decrease in tension with time. Two exceptions are low temperature (27°C) and high rate (180/min.); under either of these conditions a steady level of tension is maintained for several hours or more. The response of the isolated rat papillary muscle to various physiological alterations is consistent and reproducible if variations in size are considered.

Effects of rate and rhythm on contraction of rat papillary muscle.

The unusual relationship between frequency of contraction and tension developed by the isolated rat papillary muscle has been studied in detail. The progressive decrease in tension with increasing rate is unrelated to the size or weight of the muscle and is not changed by alterations in the ionic composition of the perfusion medium. The force-frequency relationship is also unchanged by addition of plasma, epinephrine or digitalis to the perfusion medium. Rat papillary muscle is similar to other preparations of cardiac muscle with respect to recovery of contractility and the development of rest contractions and postextrasystolic potentiation.

�ber die �nderung der Kontraktionsamplitude des elektrisch gereizten Rattenpapillarmuskels nach einer Reizpause oder einer Periode hochfrequenter Reizung

Isolated rat papillary muscles were stimulated electrically in a 50 ml. Tyrode bath at 37°C. Potentiation of contractile force following a period of rest and post-stimulation potentiation were studied.