The contractions induced in rat and guinea-pig aortic strips by the α2-adrenoceptor selective agonists B-HT 920 and UK 14,304 are mediated by α1-adrenoceptors

Beckeringh, J. J.; Thoolen, Mjmc; Dejonge, A; Wilffert, Bob; Timmermans, P.B.M.W.M.; Vanzwieten, Pa

doi:10.1016/0014-2999(84)90394-7

Cited by 40 publications

(20 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, this is unlikely, because the Schild plot analyses clearly demonstrated the existence of only a, -adrenoceptors in the mesenteric arteries from the two strains (Table 4). Selective a2-adrenoceptor agonists in cluding clonidine have been reported to behave as partial agonists of a, -adreno ceptors in several vascular tissues (23,34,35). Also, in the present study clonidine behaved as a partial agonist of a, -adreno ceptors in the mesenteric arteries from both strains.…”

Section: Discussionsupporting

confidence: 63%

Comparison of Inhibitory Effects of Calcium Channel Blockers and That of a Calmodulin Antagonist in Strips of Mesenteric Arteries from Spontaneously Hypertensive and Normotensive Rats

Asano

Masuzawa

Kojima

et al. 1988

Japanese Journal of Pharmacology

View full text Add to dashboard Cite

Abstract-Effectsof calcium channel blockers and of calmodulin antagonist on the contractile responses to norepinephrine (NE) were compared between strips of mesenteric arteries from 6 and 14-week-old spontaneously hypertensive rats (SHR) and age-matched, normotensive Wistar-Kyoto rats (WKY). The ratio of the maximum contraction developed by NE to that by 60 mM KCI was significantly increased in strips from 14-week-old SHR. Niludipine, verapamil and diltiazem antagonized the maximum NE contraction to a greater extent in strips from 14-week old SHR than in those from the WKY. However, the antagonism by niludipine of the KCI or caffeine-induced contraction was not significantly different between the strips from 14-week-old SH R and those from WKY. In strips from 6-week-old rats, there was no difference in the antagonism by niludipine of the maximum NE con traction.On the other hand, the effect of W-7 on the maximum N E contraction was not significantly different between the strips from 14-week-old SHR and those from WKY. Schild plot analyses demonstrated that a,-adrenoceptors were the same for the strips from SHR and WKY. These results suggest that the enhanced maximum NE contraction in the mesenteric artery from 14-week-old SHR reflects the increased transmembrane influx of calcium, and the activity of calmodulin seems to be the same for the two strains.

show abstract

Section: Discussionsupporting

confidence: 63%

Comparison of Inhibitory Effects of Calcium Channel Blockers and That of a Calmodulin Antagonist in Strips of Mesenteric Arteries from Spontaneously Hypertensive and Normotensive Rats

Asano

Masuzawa

Kojima

et al. 1988

Japanese Journal of Pharmacology

View full text Add to dashboard Cite

show abstract

“…Thus, influx of extracellular Ca2+ does not appear to be required for the aXB-adrenoceptor-mediated positive inotropic effects. Similarly, OClB-adrenoceptor-mediated vasoconstriction elicited by full agonist in rat aorta (Beckeringh et al, 1984) and generation of inositol phosphates in rat hepatocytes (Wilson & Minneman, 1990) are insensitive to blockade of Ca2+ influx. In contrast, ryanodine which modulates Ca2+ release from the sarcoplasmic reticulum (Stern & Lakatta, 1992) decreased maximal inotropic effects of adrenaline without altering its potency, indicating the importance of Ca2+ release from the sarcoplasmic reticulum.…”

Section: Discussionmentioning

confidence: 99%

“…In some model systems of xIB-adrenoceptors such as rat aorta, full agonists can rely on mobilization of intracellular Ca2+ only whereas partial agonists require influx of extracellular Ca2" (Beckeringh et al, 1984); following partial inactivation of (lB-adrenoceptors by treatment with the alkylating agent, phenoxybenzamine, full agonists may also require influx of extracellular Ca2+ to elicit vasoconstriction (Ruffolo et al, 1991 (Del Balzo et al, 1990;Anyukhovsky & Rosen, 1991;Wang et al, 1991;Knowlton et al, 1993) we conclude that aXA-and xIB-adrenoceptors may be coexpressed in rat myocardium to activate distinct physiological responses.…”

Section: Discussionmentioning

confidence: 99%

Functional studies on α₁‐adrenoceptor subtypes mediating inotropic effects in rat right ventricle

Michel

Hanft

Groß

1994

British J Pharmacology

View full text Add to dashboard Cite

1 We have studied the a1-adrenoceptor subtypes mediating inotropic effects of adrenaline in rat right ventricle and the Ca2+ sources used to elicit these effects. (ZlA-Adrenoceptor-mediated contractile effects in rat vas deferens were studied for comparison in some cases. 2 Treatment with chloroethylclonidine did not affect the maximal P-adrenoceptor-mediated inotropic effects in rat right ventricle or the maximal mlA-adrenoceptor-mediated contractile effects in rat vas deferens; it did not alter the potency of isoprenaline in the ventricle and reduced the potency of the o-adrenoceptor antagonists in vas deferens only slightly. Treatment of right ventricular strips with CdCl2 markedly reduced resting tension and enhanced maximal inotropic effects of isoprenaline but did not affect its potency. In control ventricles the organic Ca2`entry blocker, nitrendipine and treatment with the inorganic Ca2+ entry blocker, CdCl2 did not reduce inotropic effects of adrenaline whereas ryanodine treatment inhibited them. In contrast, nitrendipine and CdCl2 treatment had major inhibitory effects in chloroethylclonidine-treated but lacked inhibitory effects in phenoxybenzamine-treated ventricular strips. 6 We conclude that inotropic effects of adrenaline in rat heart are mediated mainly by aBadrenoceptors via release of Ca2+ from an intracellular pool. Following inactivation of z1B-adrenoceptors by chloroethylclonidine treatment, alA-adrenoceptors can fully compensate and mediate inotropic effects by promoting influx of extracellular Ca2+ at least partly via voltage-operated channels. Therefore, we speculate that aB-adrenoceptors exert a tonic inhibitory effect on (XA-adrenoceptors.

show abstract

“…UK 14304 is both a partial agonist at xl -adrenoceptors and an agonist at x2-adrenoceptors (Cambridge, 1981;Beckeringh et al, 1984;Langer & Hicks, 1984). It behaved as a weak spasmogen when the endothelium was present, but became much more powerful when the endothelium was removed.…”

Section: Discussionmentioning

confidence: 99%

Influence of the vascular endothelium on agonist‐induced contractions and relaxations in rat aorta

Bullock

Taylor

Weston

1986

British J Pharmacology

136

View full text Add to dashboard Cite

1 The influence of the vascular endothelium on agonist-induced contractions and relaxations has been measured using intact segments of rat aorta. Contiguous rubbed segments were used as controls. 2 Angiotensin II, histamine, noradrenaline, U46619 and UK14304 contracted both rubbed and intact tissues. The threshold spasmogenic concentrations of these agonists were lower in rubbed tissues than in intact preparations. 3 The sensitivity and responsiveness of tissues to angiotensin II, histamine, noradrenaline and UK14304 were greater in rubbed than in intact tissues. 4 Acetylcholine and histamine relaxed the established spasms ofintact tissues but not those of rubbed preparations, These relaxant effects of acetylcholine were abolished by pre-incubation with haemoglobin. 5 In the presence of prazosin, noradrenaline or UK 14304 relaxed established contractions in intact tissues. These effects were antagonized by idazoxan or by pre-incubation with haemoglobin. 6 In intact preparations, idazoxan had no effect on the spasmogenic sensitivity and responsiveness to UK14304. 7 Pre-incubation with haemoglobin augmented the spasmogenic actions of noradrenaline, U46619 or UK 14304 in intact tissues, but had no effect on these responses in rubbed preparations. 8 Tissue concentrations of cyclic GMP were greater in intact than in rubbed tissues. A concentration of acetylcholine (10 tiM) evoking just maximal mechanical inhibition produced a significant increase in cyclic GMP concentration in intact preparations. However, no detectable changes in cyclic GMP concentration were produced by UK 14304 (10 !M) or by acetylcholine (30 nM), concentrations which were equi-effective in inhibiting mechanical activity. 9 In the presence of threshold spasmogenic concentrations of noradrenaline, the contractile effects of angiotensin II were augmented and became comparable to those observed in rubbed preparations. In the presence of greater concentrations of noradrenaline, angiotensin II always produced an additional contraction. 10 It is concluded that the presence of the vascular endothelium limits the spasmogenic action of a variety ofagonists. Although spasmogens like noradrenaline and UK 14304 can stimulate the release of endothelium-derived relaxing factor (EDRF) via M2-adrenoceptors, the inhibitory effects of EDRF largely result from the spontaneous release of this substance.

show abstract

The contractions induced in rat and guinea-pig aortic strips by the α2-adrenoceptor selective agonists B-HT 920 and UK 14,304 are mediated by α1-adrenoceptors

Cited by 40 publications

References 21 publications

Comparison of Inhibitory Effects of Calcium Channel Blockers and That of a Calmodulin Antagonist in Strips of Mesenteric Arteries from Spontaneously Hypertensive and Normotensive Rats

Comparison of Inhibitory Effects of Calcium Channel Blockers and That of a Calmodulin Antagonist in Strips of Mesenteric Arteries from Spontaneously Hypertensive and Normotensive Rats

Functional studies on α₁‐adrenoceptor subtypes mediating inotropic effects in rat right ventricle

Influence of the vascular endothelium on agonist‐induced contractions and relaxations in rat aorta

Contact Info

Product

Resources

About

The contractions induced in rat and guinea-pig aortic strips by the α2-adrenoceptor selective agonists B-HT 920 and UK 14,304 are mediated by α1-adrenoceptors

Cited by 40 publications

References 21 publications

Comparison of Inhibitory Effects of Calcium Channel Blockers and That of a Calmodulin Antagonist in Strips of Mesenteric Arteries from Spontaneously Hypertensive and Normotensive Rats

Comparison of Inhibitory Effects of Calcium Channel Blockers and That of a Calmodulin Antagonist in Strips of Mesenteric Arteries from Spontaneously Hypertensive and Normotensive Rats

Functional studies on α1‐adrenoceptor subtypes mediating inotropic effects in rat right ventricle

Influence of the vascular endothelium on agonist‐induced contractions and relaxations in rat aorta

Contact Info

Product

Resources

About

Functional studies on α₁‐adrenoceptor subtypes mediating inotropic effects in rat right ventricle