AJP - Regulatory, Integrative and Comparative Physiology, Vol 246, Issue 2 205-R210, Copyright © 1984 by American Physiological Society

ARTICLES

Prostacyclin release following endoperoxide analogue infusion in the intact dog

J. Mehta, W. W. Nichols and R. Goldman

We examined the systemic and coronary hemodynamic responses after infusion of an endoperoxide analogue U 46,619 in anesthetized dogs and related the hemodynamic effects to the release of thromboxane A2 (TXA2) and prostacyclin (PGI2). Immediately after U 46,619 infusion, increases in mean arterial and left ventricular end-diastolic pressures (LVEDP) occurred, whereas coronary and aortic blood flows were unchanged. Calculated vascular resistances in the systemic and coronary vascular beds increased significantly. At 3-5 min after infusion, mean arterial pressure and LVEDP spontaneously decreased and vascular resistances also declined, whereas coronary and aortic blood flows were unchanged. Simultaneously measured plasma TXB2 and 6-keto-PGF1 alpha (stable hydrolysis metabolites of TXA2 and PGI2, respectively) increased in the femoral and coronary arterial blood samples in conjunction with the vasoconstrictor effects. At 3-5 min, plasma 6-keto-PGF1 alpha concentrations showed a further increase, whereas TXB2 concentrations slightly decreased, suggesting release of PGI2 as a possible mechanism of vasodilation. To examine this possibility, nine dogs were treated with cyclooxygenase inhibitors (aspirin or indomethacin) and given U 46,619. In these animals neither vasoconstrictor nor vasodilator effects were observed. Plasma TXB2 and 6-keto-PGF1 alpha concentrations also did not increase after U 46,619. These data show that the vasoconstrictor and platelet aggregatory agent U 46,619 results in PGI2 release in the dog. Release of PGI2 may be a protective and autoregulatory mechanism in the canine systemic and coronary vascular beds.

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				L.-W. Fu, Z.-L. Guo, and J. C. Longhurst Undiscovered role of endogenous thromboxane A2 in activation of cardiac sympathetic afferents during ischaemia J. Physiol., July 1, 2008; 586(13): 3287 - 3300. [Abstract] [Full Text] [PDF]