Blood-Borne Vasoconstrictor Stimulates Release of [ 14 C]Arachidonate from Prelabeled Isolated Perfused Rabbit Gastrocnemius Muscle 1

Abstract

The effect of a blood-borne vasoconstrictor on vascular resistance and arachidonate release was examined using isolated, perfused rabbit gastrocnemius muscle. Replacement of blood by perfusion with Tyrode's solution caused a marked drop in vascular resistance. Addition of rabbit plasma or the plasma factor partially purified from human blood restored vascular resistance in a concentration dependent manner. The pressor effect of the plasma factor was unaffected by concentrations of phentolamine (2.5 μg.ml^-1) and sar¹-ala⁸-angiotensin II (75 μg.ml^-1) sufficient to completely block the effects of norepinephrine and angiotensin II, respectively. However, the pressor effects of the factor were inhibited by indomethacin in a concentration-dependent manner. The factor produced a concentration dependent (r = 0.95, n = 12) increase in release of [¹⁴C]arachidonate from prelabeled preparations. This release was blocked by indomethacin. These results are consistent with the hypothesis that the pressor effects of the factor result from its effects upon arachidonate metabolism.