Potentiation of purinergic transmission by angiotensin in prostatic rat vas deferens.
1. Angiotensin II (AII) elicited only a minute, if any, direct contractile response in smooth muscle cells of prostatic rat vas deferens, but it potentiated contractile responses to field stimulation. 2. Angiotensin-potentiated contractile response to field stimulation was concentration-dependent, and the order of potency was AII > AIII approximately AI. The EC50 of AII was 8.11 +/- 2.79 nM. 3. AII did not modify the contractile response of exogenous noradrenaline (NA) on non-stimulated prostatic vas deferens. Furthermore, the concentration-response curve for AII-potentiated contractile responses to field stimulation in reserpine-treated rats did not significantly differ from the control group. 4. Desensitization of purinoceptors with 30 microM alpha, beta-methylene-ATP almost completely abolished the potentiation of the contractile response to field stimulation by AII. 5. The response to AII in the prostatic rat vas deferens was blocked by the AT1 selective antagonist losartan, but not by the AT2 selective antagonist CGP 42112. Losartan acted as a competitive antagonist with a pA2 value of 8.75. 6. In conclusion, AII potentiated purinergic transmission in the prostatic rat vas deferens via the AT1 receptor.
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Department of Biochemistry, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong.
Wan
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Cheung
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WT
D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology; D000803:Angiotensin I / Q000037:antagonists & inhibitors; D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D001713:Biphenyl Compounds / Q000494:pharmacology; D004558:Electric Stimulation; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D019808:Losartan; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D009842:Oligopeptides / Q000494:pharmacology; D011467:Prostate / Q000502:physiology*; D011480:Protease Inhibitors / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000187:drug effects*; D012110:Reserpine / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects*; D013777:Tetrazoles / Q000494:pharmacology; D014649:Vas Deferens / Q000294:innervation* / Q000502:physiology
D018759:Adrenergic Uptake Inhibitors; D001713:Biphenyl Compounds; D007093:Imidazoles; D009842:Oligopeptides; D011480:Protease Inhibitors; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D013777:Tetrazoles; D000804:Angiotensin II; C060894:CGP 42112A; D012110:Reserpine; D000803:Angiotensin I; D019808:Losartan; D009638:Norepinephrine