The heart as an endocrine gland

Area of Science:

• Cardiovascular Endocrinology
• Molecular Cardiology
• Renal Physiology

Background:

• Morphological studies revealed specific granules in mammalian atrial cardiocytes, distinct from lysosomes.
• These granules exhibited protein composition and incorporation patterns characteristic of peptide-secreting endocrine cells.
• Granule content in rat atria correlated with sodium and water balance.

Purpose of the Study:

• To investigate the endocrine function of the heart atria.
• To identify and characterize the natriuretic and diuretic factors produced by the atria.
• To elucidate the physiological roles and molecular mechanisms of atrial natriuretic factors.

Main Methods:

• Morphological analysis of atrial cardiocytes.
• Biochemical characterization of atrial granules (protein composition, isotope incorporation).
• Extraction and purification of atrial natriuretic factors.
• Gene cloning, sequencing, and chromosomal localization of the atrial natriuretic factor (ANF) gene.
• In vivo and in vitro studies on the effects of native and synthetic ANF.

Main Results:

• Atrial extracts demonstrated significant natriuretic and diuretic effects.
• The atrial natriuretic hormone (ANF) was purified, sequenced, synthesized, and its cDNA and gene cloned.
• ANF exerts wide-ranging physiological effects on the kidney, vasculature, adrenal cortex, and pituitary, potentially via guanylate cyclase stimulation.
• The human ANF gene is located on chromosome 1p36.

Conclusions:

• The atria function as a peptide-secreting endocrine gland, producing atrial natriuretic factor (ANF).
• ANF plays a critical role in regulating sodium and water balance, blood pressure, and cardiovascular function.
• Emerging evidence links ANF to physiopathological conditions like hypertension and heart failure.