CORRELATION BETWEEN PHOSPHATIDYLINOSITOL LABELING AND CONTRACTION IN RABBIT AORTA - EFFECT OF ALPHA-1 ADRENERGIC ACTIVATION

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 222  (1) , 258-261
Abstract
Activation of rabbit aortic strips with .alpha.-adrenergic agonists increased the labeling {with[32P]Pi} of phosphatidylinositol (Pi) and phosphatidic acid and contracted the vascular preparations in dose-related fashion. Epinephrine, norepinephrine and methoxamine produced maximal effects, whereas clonidine behaved as partial agonist and B-HT 933 (2-amino-6-ethyl-4,5,7,8-tetrahydro-6H-oxazolo-[5,4-d]azepine dihydrochloride) was almost without activity in the 2-experimental models used. Phenylephrine was a full agonist in producing contraction, but failed to elicit the maximal increase in Pi labeling. The EC50 [median effective concentration] values to produce contraction of aortic strips were lower for all agonists than those required to increase the incorporation of radioactive phosphate into Pi, but there was a good correlation between the two sets of data. The increased Pi labeling and contraction of aortic strips induced by epinephrine were antagonized by prazosin and yohimbine in dose-related fashion, but the first .alpha.-blocker was about 3 orders of magnitude more potent than the second in antagonizing the 2 effects. Both stimulation of Pi labeling and contraction are evidently mediated through activation of .alpha.-adrenoceptors in rabbit aorta.