Mechanism of action of angiotensin II in human isolated subcutaneous resistance arteries.
1. Human isolated subcutaneous arteries were mounted in a myograph and isometric tension measured. In some experiments, intracellular calcium [Ca(2+)]i was also measured using fura-2. 2. Angiotensin II (100 pM - 1 microM) increased [Ca(2+)]i and tone in a concentration-dependent manner. The effects of angiotensin II (100 nM) were inhibited by an AT1-receptor antagonist, candesartan (100 pM). 3. Ryanodine (10 microM), had no effect on angiotensin II-induced responses, but removal of extracellular Ca(2+) abolished angiotensin II-induced rise in [Ca(2+)]i and tone. Inhibition of Ca(2+) entry by Ni(2+) (2 mM), also inhibited angiotensin II responses. The dihydropyridine, L-type calcium channel antagonist, amlodipine (10 microM), only partially attenuated angiotensin II responses. 4. Inhibition of protein kinase C (PKC) by chelerythrine (1 microM), or by overnight exposure to a phorbol ester (PDBu; 500 nM) had no effect on angiotensin II-induced contraction. 5. Genistein (10 microM), a tyrosine kinase inhibitor, inhibited angiotensin II-induced contraction, but did not inhibit the rise in [Ca(2+)]i, suggesting that at this concentration it affected the calcium sensitivity of the contractile apparatus. Genistein did not affect responses to norepinephrine (NE) or high potassium (KPSS). 6. A selective MEK inhibitor, PD98059 (30 microM), inhibited both the angiotensin II-induced contraction and rise in [Ca(2+)]i, but had no effect on responses to NE or KPSS. 7. AT1 activation causes Ca(2+) influx via L-type calcium channels and a dihydropyridine-insensitive route, but does not release Ca(2+) from intracellular sites. Activation of tyrosine kinase(s) and the ERK 1/2 pathway, but not classical or novel PKC, also play a role in angiotensin II-induced contraction in human subcutaneous resistance arteries.
Garcha
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RS
Department of Clinical Pharmacology, National Heart & Lung Institute, Imperial College of Science, Technology & Medicine, St Mary's Hospital, South Wharf Road, London W2 1NY, UK. r.garcha@ic.ac.uk
Sever
P S
PS
Hughes
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AD
D017311:Amlodipine / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D001158:Arteries / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D001562:Benzimidazoles / Q000494:pharmacology; D001713:Biphenyl Compounds; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004095:Dihydropyridines / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D009532:Nickel / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D012867:Skin / Q000098:blood supply; D013777:Tetrazoles / Q000494:pharmacology; D014655:Vascular Resistance; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D001562:Benzimidazoles; D001713:Biphenyl Compounds; D002121:Calcium Channel Blockers; D004095:Dihydropyridines; D005419:Flavonoids; D013777:Tetrazoles; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D012433:Ryanodine; D017311:Amlodipine; C038806:1,4-dihydropyridine; D009532:Nickel; D019833:Genistein; D011188:Potassium; C081643:candesartan; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D002118:Calcium; D009638:Norepinephrine