LOSARTAN REDUCES VASORELAXANT EFFECT OF ATRIAL NATRIURETIC PEPTIDE IN AORTA BASAL TONE

ROMANO, LILIANA; COVIELLO, ALFREDO; MARIA DE LOS ANGELES PERAL

CLINICAL AND EXPERIMENTAL HYPERTENSION

Editorial Marcel Dekker Inc

Lugar: Nueva York , USA; Año: 1999 vol. 21 p. 1257 - 1271

1064-1963

LOSARTAN REDUCES  VASORELAXANT EFFECT OF ATRIAL NATRIURETIC PEPTIDE IN AORTA  BASAL TONE  ASBTRACT     Atrial natriuretic peptide (ANP) has a vasorelaxant effect on  non-contracted rings of  rabbit  aorta previously sensitized with angiotensin II (Ang II). We investigated whether this  Ang II-sensitization induces a calcium-dependent basal tone in non-contracted smooth muscle and the  rol in this response of antagonists of Ang II type 1 (AT1)  and Ang II type (AT2 ) receptors. Calcium-free Krebs, significantly  lowered  basal tone  in   thoracic rabbit aorta after complete recovery from a previous challenge with Ang II;  this change was partially  reversed by reexposure to calcium-containing media. The reduction in basal tone elicited by calcium-free Krebs was similar to that previously obtained with ANP and  lower to that obtained by treatment  with calcium-free Krebs+ EGTA+sodium nitroprusside (SNP).  No one of these treatments had effect on basal tension in rings from rabbit aorta unpreviously exposed to Ang II. The vasorelaxant effect of ANP or  calcium-free Krebs + EGTA + SNP on basal tone of rabbit aorta could not be obtained when the calcium was previously removed. The AT1  receptor antagonist (losartan) did not alter isometric tension in either basal or  sensitized Ang II aorta, however it reduced the Ang II-contractile response. On the other hand, the reduction in basal tone elicited by  ANP was significantly atenuated when the rings were pretreated with losartan. This inhibition could not be obtained with the AT2 receptor antagonist PD 123319. The effect of ANP is due to  Ang II contribution to the development of an increased calcium-dependent basal tone  in aortic rings through the stimulation of AT1 receptors.