Different response of ANP secretion to adrenoceptor stimulation in renal hypertensive rat atria.
Sympathetic nervous system and atrial natriuretic peptide (ANP) system play fundamental roles in the regulation of cardiovascular functions. Overactivity of sympathetic nervous system can lead into cardiovascular diseases such as heart failure and hypertension. The present study aimed to define which adrenergic receptors (ARs) affect atrial contractility and ANP release and to determine their modification in renal hypertensive rat atria. An alpha(1)-AR agonist, cirazoline increased ANP release with positive inotropism. These alpha(1)-AR agonist-mediated responses were attenuated by the alpha(1A)-AR antagonist, but not by the alpha(1B)- or alpha(1D)-AR antagonist. An alpha(2)-AR agonist, guanabenz and clonidine increased ANP release with negative inotropism and decreased cAMP level. The order of potency for the increased ANP release was cirazoline>>phenylephrine=guanabenz>>clonidine. In contrast, a beta-AR agonist, isoproterenol decreased ANP release with positive inotropism and these responses were blocked by the beta(1)-AR antagonist but not by the beta(2)-AR antagonist. The increased cAMP level by isoproterenol was suppressed by pretreatment with both beta(1)- and beta(2)-AR antagonists. In renal hypertensive rat atria, the effects of isoproterenol on atrial contractility, ANP release, and cAMP level were attenuated whereas the effect of cirazoline on ANP release was unaltered. Atrial beta(1)-AR mRNA level but not alpha(1A)-AR mRNA level was decreased in renal hypertensive rats. These findings suggest that alpha(1A)- and beta(1)-AR oppositely regulate atrial ANP release and that atrial beta(1)-AR expression/function is impaired in renal hypertensive rats.
Yuan
Kuichang
K
Department of Physiology, Medical School, Chonbuk National University, Jeonju 561-180, Republic of Korea.
Rhee
Kyoung-Suk
KS
Park
Woo Hyun
WH
Kim
Soo Wan
SW
Kim
Suhn Hee
SH
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D003000:Clonidine / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006143:Guanabenz / Q000494:pharmacology; D006325:Heart Atria / Q000187:drug effects* / Q000378:metabolism; D006977:Hypertension, Renal / Q000503:physiopathology*; D007093:Imidazoles / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D011941:Receptors, Adrenergic / Q000187:drug effects*; D013997:Time Factors
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D007093:Imidazoles; D012333:RNA, Messenger; D011941:Receptors, Adrenergic; D010656:Phenylephrine; D009320:Atrial Natriuretic Factor; D000242:Cyclic AMP; D006143:Guanabenz; D007545:Isoproterenol; D003000:Clonidine; C014282:cirazoline