Atrial-specific granule number and plasma atrial natriuretic peptide in rats: effects of beta-adrenoceptor blockade and sodium intake.
An interrelationship between atrial natriuretic peptide (ANP) and the renin-angiotensin system has been established. Both of these hormonal systems are modulated by sodium balance. The role of the beta-adrenoceptor in the regulation of release of ANP is not clear. We therefore undertook a study to examine changes in atrial-specific granule number and plasma ANP level following beta-adrenoceptor blockade in rats on low and high sodium intakes. A low-sodium diet, as compared with a high-sodium diet, elevated right and left atrial-specific granule number (right atria 54.6 +/- 8.7 vs. 42.3 +/- 5.7; left atria 47.7 +/- 7.7 vs. 30.6 +/- 3.4 granules/unit area) and plasma renin activity (28 +/- 3.7 vs. 5.4 +/- 0.8 ng AI/ml/hr). Plasma ANP levels were lower in the low-sodium animals (98 +/- 34 vs. 345 +/- 38 pg/ml). When treated with the nonspecific beta-adrenoceptor blocker propranolol, the elevated plasma renin activity and atrial-specific granule number in rats on a low sodium intake were significantly less. Neither of these parameters changed in rats on a high sodium intake. Conversely, propranolol treatment resulted in lower plasma ANP levels in rats with high sodium intake. The already-suppressed plasma ANP level in rats on a low-sodium diet was unaltered with beta-adrenoceptor blockade. The results suggest that dietary sodium intake is an important determinant of the response of atrial-specific granule number and plasma ANP levels following beta-adrenoceptor blockade with propranolol.
Penner
S B
SB
Department of Internal Medicine, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Thliveris
J A
JA
McKenzie
J K
JK
Smyth
D D
DD
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000450:Aldosterone / Q000097:blood; D000818:Animals; D016275:Atrial Function; D009320:Atrial Natriuretic Factor / Q000097:blood*; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure*; D004305:Dose-Response Relationship, Drug; D006325:Heart Atria / Q000187:drug effects / Q000648:ultrastructure*; D008297:Male; D008854:Microscopy, Electron; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System / Q000187:drug effects / Q000502:physiology; D012964:Sodium / Q000494:pharmacology; D012982:Sodium, Dietary / Q000008:administration & dosage
D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D012982:Sodium, Dietary; D000450:Aldosterone; D009320:Atrial Natriuretic Factor; D012964:Sodium; D011433:Propranolol; D012083:Renin