Abstract
We have previously shown decreased Ca accumulation in crude cardiac sarcoplasmic reticulum (SR) vesicles isolated from fetal sheep. However, recent data indicate that the cardiac SR is subspecialized and that these crude preparations are quite heterogeneous. To further define developmental changes in SR Ca transport, SR vesicles from fetal and maternal sheep hearts were seperated by sucrose density gradient centrifugation into free (F) and junctional (J) fractions.
The FSR vesicles displayed a high density of Ca pumps and high Ca uptake that was insensitive to ryanodine. In contrast, although Ca uptake was decreased in JSR vesicles, uptake increased markedly in the presence of ryanodine. Gel electrophoresis showed selective enrichment of JSR vesicles with the Ca binding protein, calsequestrin. CaATPase activity and maximal Ca uptake were decreased 30-50% in fetal FSR and JSR (p<0.05). These data indicate that previously described differences in Ca transport in cardiac SR vesicles isolated from fetal and maternal sheep persist in our highly purified preparations of FSR and JSR. Further characterization of these SR subpopulations should enable us to better define developmental changes in SR function. *meanĀ±SD, n=3.
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Mahony, L., Moulton, M. SEPARATION OF CARDIAC SARCOPLASMIC RETICULUM FROM FETAL AND MATERNAL SHEEP INTO FREE AND JUNCTIONAL SUBPOPULATIONS. Pediatr Res 21 (Suppl 4), 192 (1987). https://doi.org/10.1203/00006450-198704010-00153
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DOI: https://doi.org/10.1203/00006450-198704010-00153