Abstract
The ability of atria, removed from Sprague-Dawley rats at ages 1–21 days, to take up and store catecholamines was studied to correlate this activity with the previously observed physiologic immaturity of the cardiac sympathetic nervous system in the neonate. The cardiac tissue was incubated in Krebs-Henseleit bicarbonate buffer containing 10−5 M iproniazid and 10−7 M H3-nor-epinephrine (H3NE). Total uptake and subcellular distribution at 1, 4, 7, 14, and 21 days were determined at various time intervals between 5 and 30 minutes. Uptakes at O°C. served as controls.
Uptake rates were expressed on a per gram wet weight basis. There was a small amount of uptake observed during the first post-natal day (0.515 nanagrams/minute) which increased only slightly by 4 days of age (0.683 ng/min). The most significant change occurred between 4 and 7 days (115%). Uptakes at 7, 14, and 21 days were similar to adult values. Since reserpine effectively blocks uptake of catecholamines into the storage granulee, 10−5 M reserpine was added to the incubation media to determine the role of the granule in the previously observed uptake. Reserpine inhibited the 30 minute uptake 57% during the first day of life increasing to 70% inhibition by 7 days of age. The utake observed in the microsomal (granular) fraction showed similar suggest a marked inability of the newborn rat heart to take up and store norepinephrine due to either decreased number of storage vesicles or an immature uptake mechanism in the granule.
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Atwood, G., Kirshner, N. & Spach, M. Catecholamine uptake and storage of the newborn rat heart during post-natal development. Pediatr Res 5, 425 (1971). https://doi.org/10.1203/00006450-197108000-00226
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DOI: https://doi.org/10.1203/00006450-197108000-00226