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  • 1
    Electronic Resource
    Electronic Resource
    Ontogenetic differences in cardiac sensitivity to verapamil in rats (1986)
    Springer
    Pediatric cardiology 7 (1986), S. 25-29 
    Details
    ISSN: 1432-1971
    Keywords: Verapamil ; Rat heart ; Ontogenetic development ; Age effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The degree of a negative inotropic response of the isolated right ventricle to verapamil as well as the mortality rate were studied in rats during their postnatal development. Male Wistar rats aged 3, 15, 30, and 90 days were used. The isolated right ventricle was incubated in a glucose-free solution with a mixture of 95% O2 and 5% CO2 and electrically stimulated. The amplitude of isotonic contractions (AIC) was registered. In 90-day-old rats, AIC was 74.1±6.2% of initial amplitude 45 min after administration of verapamil; in 30-day-old, 41.1±6.4%; in 15-day-old, 38.2±4.1%; and in 3-day-old rats, only 2.6±1.5. The difference between the 3-day-old rats and all older groups was statistically highly significant. The mortality rate of verapamil-treated rats increased with decreasing age of animals. It is concluded that the sensitivity of the rat myocardium to verapamil is age dependent: the negative inotropic effect of this drug increases with decreasing age of the animal. This indicates a possible risk in the therapeutic use of verapamil when given to newborns and infants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315478
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Thyroid control of contractile function and calcium handling in neonatal rat heart (1992)
    Springer
    Pflügers Archiv 421 (1992), S. 26-31 
    Details
    ISSN: 1432-2013
    Keywords: Heart function ; Postnatal development ; Thyroid hormones ; Sarcolemma ; Sarcoplasmic reticulum ; Ca2+ transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Newborn rats were rendered hyperthyroid (daily subcutaneous injections of L-triiodothyronine, 10 μg 100 g−1 body weight) or hypothyroid (0.05% 6-n-propyl-2-thiouracil in drinking water to nursing mothers) during the first 3 weeks of postnatal life. Compared with the euthyroid group, hyperthyroidism resulted in: (1) cardiac enlargement with right ventricular preponderance, (2) increased cardiac contractile function, (3) increased Ca2+ uptake by the sarcoplasmic reticulum (SR), (4) decreased sensitivity to the negative inotropic effect of verapamil and (5) greater inhibition of contractile function by ryanodine. Hypothyroidism generally resulted in opposite changes. The data suggest that the development of the heart and its contractile function during early postnatal life depends on the plasma level of thyroid hormones. In particular, the relative contribution of the SR and sarcolemmal Ca2+ transport to the control of cardiac contractility seems to be markedly affected by altered thyroid states. The postnatal maturation of the SR function is accelerated in hyperthyroidism but retarded in hypothyroidism. Consequently, hyperthyroid hearts appear to be less dependent and hypothyroid ones more dependent on trans-sarcolemmal Ca2+ fluxes when compared with age-matched euthyroid animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374729
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    Paper (German National Licenses)
    Fulltext
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