Prevalence and Turnover of Peptidylglycineα-amidating Monooxygenase mRNA in Atrial Cardiomyocytes

Peptidylglycineα-amidating monooxygenase (PAM), the enzyme responsible for theα-amidation of neuroendocrine peptides, is more prevalent in the atrium of the heart than in pituitary or brain. RNase protection assays indicate that PAM transcripts account for approximately 0.5 % of the mRNA in the neonatal atrium and 0.06 % of the mRNA in the neonatal ventricle. In primary atrial cardiomyocyte cultures PAM mRNA turns over slowly, with a half-life of approximately 20 h. Levels of PAM mRNA in primary atrial cardiomyocytes are increased to 165 % of control upon treatment with dexamethasone and decreased to 63 % of control upon treatment with thyroid hormone.