Cardiac natriuretic peptides and development of hereditary hypertension in rats.

Ultrastructure of the right atrial cardiomyocytes of suckling ISIAH rats was studied to clarify the role of cardiac natriuretic peptides in hypertension development during the period when blood pressure is not yet elevated. Cardiomyocytes diameter was significantly greater, Golgi complex was more developed, and granules in the sarcoplasm were more abundant in ISIAH rats as soon as on postnatal day 12 in comparison with age-matched normotensive animals. The smaller diameter of granules and their qualitative composition (ratio of forming, mature, and dissolving forms) attest to active synthesis and release of secretory product. In 21-day-old ISIAH rats, granule size and qualitative composition reflected increased accumulation of hormones in the cells. Thus, morphological features of increased production of natriuretic peptides in the right atrial myocytes were revealed in rats during the first postnatal month before manifestation of hereditary hypertension.