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PubMed · 6232858

Developmental changes in myocardial mechanical function and subcellular organelles.

T Nakanishi·J M Jarmakani
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Abstract

This study investigates the developmental changes in myocardial mechanical function and the function of subcellular organelles. Mechanical function was determined at various Ca2+ concentrations ( [Ca2+]0) in the isolated, arterially perfused heart of the fetus (28th day of gestation), newborn (3-5 day old), and adult rabbit. Maximal force of contraction in the fetus (observed at 7.5 mM [Ca2+]0) was significantly less than that in the newborn (observed at 30 mM ( [Ca2+]0), and both the fetus and newborn values were significantly less than that in the adult (observed at 15 mM [Ca2+]0). The myofibrillar content in the fetus and ATPase activity in the fetus and newborn were significantly less than in the adult at pCa 4 and 5 where this enzyme was maximally activated. Both the amount of sarcoplasmic reticulum (SR) and SR Ca2+ uptake per gram of muscle increased with age. Mitochondrial Ca2+ uptake was not observed at pCa more than 6 (physiological range) in all age groups. At pCa less than 6, mitochondrial Ca2+ uptake (per g muscle) in the newborn was significantly greater than in the fetus and adult. Ca2+ uptake by crude homogenate in the newborn was also greater than in the fetus and adult. These data suggest that the age-related change in myocardial contractility is due to the differences in intracellular Ca2+ concentration and myofibrillar content as well as ATPase activity. Intracellular Ca2+ concentration may vary with development depending on the relative capability of Ca2+-releasing system and Ca2+-sequestering system.

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Adenosine TriphosphatasesAnimalsCalciumFemaleHeartLanthanumMyocardiumPregnancyRabbitsSarcoplasmic ReticulumSubcellular FractionsTemperatureJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.

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T Nakanishi, J M Jarmakani. 1984. Developmental changes in myocardial mechanical function and subcellular organelles.. https://doi.org/10.1152/ajpheart.1984.246.4.h615

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