Inhibition of Ang II and renal sympathetic nerve influence dopamine‐and isoprenaline‐induced renal haemodynamic changes in normal Wistar–Kyoto and spontaneously hypertensive rats

Abstract

1. This study was undertaken to elucidate the effects of inhibiting the renin-angiotensin system (RAS) with losartan, and acute unilateral renal denervation on renal haemodynamic responses to intrarenal administration of vasoconstrictor doses of dopamine and vasodilator doses of isoprenaline in Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). 2. Acute unilateral renal denervation of the left kidney in rats was confirmed by a drop in the renal vasoconstrictor response to renal nerve stimulation (P < 0.05) along with diuresis and natriuresis. Rats were pretreated with losartan for 7 days and thereafter animals fasted overnight were anaesthetized (sodium pentobarbitone, 60 mg/kg i.p.) and acute renal haemodynamic responses studied. 3. Dose-response curves were constructed for dopamine and isoprenaline that induced falls or increases in renal blood flow, respectively. It was observed that renal vascular responses were greater in the denervated as compared with rats with intact renal nerves (all P < 0.05). Dopamine-induced renal vasoconstrictor responses were markedly lower in losartan-treated denervated WKY and SHR compared with their untreated counterparts (all P < 0.05). It was also observed that in losartan-treated and denervated WKY rats the vasodilatory responses to isoprenaline were markedly lower compared with untreated rats (all P < 0.05). However, in SHR, under the same conditions, there was no difference in the renal response to isoprenaline whether or not rats were treated with losartan (P > 0.05). 4. The data obtained showed that the renal vasoconstrictor effect of dopamine depends on intact renal nerves and RAS in WKY and SHR. Isoprenaline responses were likewise sensitive to renal denervation and RAS inhibition in WKY rats but not SHRs. Our observations reveal a possible relationship between renal AT(1) receptors and alpha(1)-adrenoceptors in WKY and SHR. There is also evidence to suggest an interaction between renal beta-adrenoceptors and AT(1) receptors in WKY rats.

Influence of sympathetic and AT1‐receptor blockade on angiotensin II and adrenergic agonist‐induced renal vasoconstrictions in spontaneously hypertensive rats

“…The effectiveness of the surgical procedure used in acute unilateral denervation was evaluated by the electrical stimulation of the renal nerves before and after denervation. Prior to surgery, electrical stimulation of the renal nerves caused a large fall in RBF, this was abolished following section of the nerves (Abdulla et al . 2008a,b).…”

“…Finally, 10% phenol in absolute alcohol was used in coating the remaining covering tissues (Rademacher et al. 1986, Abdulla et al . 2008a,b).…”

Dopamine and Renal Function and Blood Pressure Regulation

“…D 4 R, located on the postjunctional site of guinea pig vas deferens, enhances contractile responses to agonists without affecting muscle tone (416). D 2 -like receptor agonists may also constrict renal vessels in volume-loaded rats (305) that is dependent on intact renal nerves and the renin angiotensin system (1). …”

Vascular Reactivity ConcerningOrthosiphon stamineusBenth-Mediated Antihypertensive in Aortic Rings of Spontaneously Hypertensive Rats

“…PE has predominantly α 1 -postjunctional receptors in rat's aorta [14]. Since PE is a selective α 1 -adrenergic receptor agonist and losartan is AT 1 receptor blocker, there is possible relationship between AT 1 and α 1 receptors [15]. In addition, crosstalk between AT 1 and α 1 receptors in the smooth muscle of rabbit aorta is endothelium dependent [16].…”