Analysis of action mechanism of atrial matri-uretic peptide in perfused heart and tissue-cultured myocytes -in vivo analysis using a muti emission-reflexion analyzer and NMR-

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The effect of rANP(rat atrial natriuretic peptide) on mitochondrial respiratory state in perfused rat heart.Purified mitochondria was used for the assay of oxidative phosphorylation using oxygraph. rANP at the concentration of 10ng/ml did not affect the respiratory function of heart mitochondria in vitro. Perfused rat heart with Langendorf apparatus was then used for the assay of mitochondrial respiratory function. A multi-light-emission-reflection monitoring system was used for this assay, and oxidation-reduction state of cytochromes c, al-a3, b, myoglobin was monitored through the experiment. rANP at 10ng/ml significantly prolonged the transient time from oxidative state to reduced state which was induced by ischemic condition.This indicates that rANP made heart cells more resistant to ischemic damage through the protection of mitochondrial respiratory function. Electro-microscopic study also supported these results.The effect of hANP(human atrial natriuretic peptide) on phosphorylation and intracellular concentration of calcium ion of CPAE cells derived from bovine pulmonary artery endothelium.Cultured CAPE cells were used for the phosphorylation assay under aerobic and anerobic condition using [32P orthophosphate in the culture medium. hANP at a concentration of 10ng/ml was added to the medium and the phosphorylation was analyzed and compared. hANP did not affect the phosphorylation under the aerobic condition. In contrast, hANP recovered to some extent the reduced phosphorylation which occurred under anerobic condition.The concentration of intracellular calcium ion([Ca i) was monitored by a calcium-specific fluorescent dye, Fura 2, and a calcium imaging analysis was performed. Under the anerobic condition, [Ca i raised by 30-50% as compared to that under aerobic condition. hANP(10ng/ml) reduced the incraese of [Ca i to 20-30%. hANP itself did not stimulate the increase of [Ca i.