Cardiac hormones: morphology and biochemistry.

Area of Science:

• Cardiovascular Endocrinology
• Cell Biology
• Molecular Endocrinology

Background:

• The heart possesses specialized endocrine cells within the atrial appendage.
• These myoendocrine cells are crucial for synthesizing and secreting cardiac hormones.

Purpose of the Study:

• To elucidate the synthesis and secretion pathway of cardiac hormones in myoendocrine cells.
• To detail the processing of preprohormone to active circulating forms.

Main Methods:

• Ultrastructural analysis of myoendocrine cells.
• Immunocytochemical analysis to identify cellular components and hormone precursors.

Main Results:

• Myoendocrine cells exhibit a specialized secretory apparatus.
• Cardiac hormones are synthesized as preprohormone in the endoplasmic reticulum, processed to prohormone (cardiodilatin/gamma-atrial natriuretic polypeptide - CDD/ANP) in the Golgi, and stored in secretory granules.
• The active circulating form, cardiodilatin 99-126/alpha-ANP, is released into the bloodstream.

Conclusions:

• Myoendocrine cells are key players in cardiac endocrine function.
• The study details the molecular processing of CDD/ANP from synthesis to secretion.
• This pathway highlights the heart's role in producing circulating natriuretic peptides.