alexa Disparate effects of calcium antagonists on renal microcirculation.
Surgery

Surgery

Medical & Surgical Urology

Author(s): Hayashi K, Nagahama T, Oka K, Epstein M, Saruta T

Abstract Share this page

Abstract Although calcium antagonists reduce systemic blood pressure, the effects of calcium antagonists on renal preglomerular and postglomerular microcirculation have been suggested to differ. In the present study we examined the vasodilator action of dihydropyridine-type calcium antagonists, including nifedipine, nicardipine, amlodipine, and efonidipine, on afferent and efferent arterioles during angiotensin II (A-II)- and norepinephrine (NE)-induced renal vasoconstriction. Isolated perfused hydronephrotic kidneys were used to directly visualize renal microcirculatory response to calcium antagonists. Both A-II and NE caused marked vasoconstriction of afferent (A-II, 27 +/- 2\% decrement; NE, 28 +/- 2\% decrement) and efferent arterioles (A-II, 25 +/- 4\% decrement; NE, 22 +/- 2\% decrement). The subsequent addition of nifedipine, nicardipine, and amlodipine reversed the afferent arteriolar vasoconstriction in a dose-dependent manner, and elicited complete vasodilation at 10(-6) M. In contrast, efferent arteriolar vasoconstriction was relatively refractory to the dilator action of these calcium antagonists; maximal dilation observed at 10(-6) M was 21 +/- 1\% (A-II) and 22 +/- 3\% (NE) for nifedipine, 25 +/- 3\% (A-II) and 20 +/- 6\% (NE) for nicardipine, and 39 +/- 6\% (A-II) and 37 +/- 3\% (NE) for amlodipine. In striking contrast, efonidipine dilated not only afferent arterioles, but also efferent arterioles in a dose-dependent manner. At 10(-6) M, efonidipine completely inhibited the afferent (A-II, 89 +/- 7\% reversal; NE, 99 +/- 8\% reversal) and efferent arteriolar vasoconstriction (A-II, 93 +/- 4\% reversal; NE, 87 +/- 9\% reversal). These findings clearly demonstrate that calcium antagonists dilate the afferent arteriole. Unlike the effects on the afferent arteriole, efferent arteriolar responsiveness to calcium antagonists differ, depending on the type of calcium antagonist. The efonidipine-induced efferent arteriolar vasodilation is probably not related to voltageoperated calcium channels, and may act, in concert with blood pressure lowering effect, to ameliorate glomerular capillary hypertension.
This article was published in Hypertens Res and referenced in Medical & Surgical Urology

Relevant Expert PPTs

Recommended Conferences

Relevant Topics

Peer Reviewed Journals
 
Make the best use of Scientific Research and information from our 700 + peer reviewed, Open Access Journals
International Conferences 2017-18
 
Meet Inspiring Speakers and Experts at our 3000+ Global Annual Meetings

Contact Us

 
© 2008-2017 OMICS International - Open Access Publisher. Best viewed in Mozilla Firefox | Google Chrome | Above IE 7.0 version
adwords