Blood pressure reducing effects of Phalaris canariensis in normotensive and spontaneously hypertensive rats.
The birdseed Phalaris canariensis (Pc) is popularly used as an antihypertensive agent. The aqueous extract of Pc (AEPc) was administered in adult normotensive Wistar rats and spontaneously hypertensive rats (SHR) and in prehypertensive young SHR (SHR(Y), 3 weeks old). Animals received AEPc (400 mg·kg(-1)·day(-1), by gavage) for 30 days, then groups were divided into 2 subgroups: one was treated for another 30 days and the other received water instead of AEPc for 30 days. AEPc reduced systolic blood pressure (SBP) in both adult groups; however, treatment interruption was followed by a gradual return of the SBP to baseline levels. SHR(Y) became hypertensive 30 days after weaning. AEPc minimized the increase in SBP in SHR(Y), but blood pressure rose to levels similar to those in the untreated group with treatment interruption. There were no changes in renal function, diuresis, or Na(+) excretion. Pc is rich in tryptophan, and the inhibition of the metabolism of tryptophan to kynurenine, a potential vasodilator factor, prevented the blood pressure reducing effect of AEPc. Moreover, AEPc significantly reduced sympathoexcitation. Data indicate that the metabolic derivative of tryptophan, kynurenine, may be a mediator of the volume-independent antihypertensive effect of Pc, which was at least in part mediated by suppression of the sympathetic tonus.
Renal Division, Federal University of São Paulo (UNIFESP), Rua Botucatu, 740, 04023-900, São Paulo, Brazil.
Clévia Santos
CS
Passos
Lucimeire Nova
LN
Carvalho
Roberto Braz
RB
Pontes
Ruy Ribeiro
RR
Campos
Olinda
O
Ikuta
Mirian Aparecida
MA
Boim
D000818:Animals; D000959:Antihypertensive Agents / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006973:Hypertension / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D007737:Kynurenine / Q000378:metabolism; D008297:Male; D031783:Phalaris / Q000737:chemistry; D010936:Plant Extracts / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D058246:Prehypertension / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D051381:Rats; D011918:Rats, Inbred SHR; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology; D013997:Time Factors; D014364:Tryptophan / Q000378:metabolism
D000959:Antihypertensive Agents; D010936:Plant Extracts; D007737:Kynurenine; D014364:Tryptophan