Inhibition of Secretory Activity of Atrial Myocytes in Hypertensive Rats after Losartan Treatment

Abstract

Male ISIAH rats with inherited stress-induced arterial hypertension (BP 174.0 ± 1.3 mm Hg) received antagonist of angiotensin II receptors losartan in a dose of 10 mg/kg/day for 16 days. Ultrastructural study of the right atrium showed signs of dramatic and pronounced inhibition of synthesis of the natriuretic peptides (changes in the composition of secretory granules and decrease in their population density and size) the atrial myocytes against the background of persistent BP decrease in hypertensive rats to 142.0 ± 4.2 mm Hg. We concluded that myoendocrine cells in rats with stable hypertension retain ability to respond adequately to distention of the atria with blood.

Morphology of Right Atrium Myocytes

“…By contrast, there was no correlation between the total content of granules and the area occupied by mitochondria or myofibrils. An enhanced endocrine activity of the secretory cardiomyocytes was observed against the background rise of arterial pressure by 23% [23], which in the view of some researches upregulates not only secretion but also the synthesis of ANP [15,21].…”

“…The role of ANP in the pathogenesis of cardiovascular diseases is ambiguous [8].The contradictory data of the study could partially be associated with the use of different methods for the determination of ANP. The few research works of atrial cardiac myocytes are devoted to their morphology only [15] or to the quantitative assessment of the hormone content without analyzing the ultrastructure of cells [16].…”