title: Blood borne vasoconstrictors lowers ratio of prostaglandin I2 to other products formed form arachidonate.
abstract: The effects of a blood borne vasoconstrictor on prostaglandin synthesis by microsomal enzyme preparations from rat aorta, heart and stomach fundus were determined. The principle product formed from arachidonate by these preparations in the absence of added vasoactive factor was prostaglandin I2 (as measured by recovery of 6-keto-prostaglandin F1 alpha). Addition of vasoactive factor stimulated overall prostaglandin synthesis and also reduced the ratio of 6-keto-prostaglandin synthesis F1 alpha to other products. No correlation was found between factor induced increases in overall synthesis and changes in this ratio. However, the factor produced a ratio which was specific for each tissue. The further the initial ratio of preparation was from its tissue specific level, the greater the effect of the factor. Blood free tissues continued considerable factor activity. Hence the variations in ratios in the absence of exogenous factor could be due to the presence of endogenous factor contaminating the preparations. Indomethacin not only inhibited overall prostaglandin synthesis but also decreased the ratio of 6-keto-prostaglandin F1 alpha to other products. Both these effects of indomethacin were counteracted by addition of exogenous factor. These results provide evidence that, in addition to their effects on the cyclooxygenase reaction, the factor and indomethacin interact a the second site; one involved in the change in ratio 6-keto-prostaglandin F1 alpha to other products.
mesh_terms: D000328:Adult; D000818:Animals; D001011:Aorta / Q000378:metabolism; D001095:Arachidonic Acids / Q000378:metabolism*; D011464:Epoprostenol / Q000378:metabolism*; D005748:Gastric Fundus / Q000378:metabolism; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008861:Microsomes / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D011453:Prostaglandins / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D001095:Arachidonic Acids; D011453:Prostaglandins; D014662:Vasoconstrictor Agents; D011464:Epoprostenol; D007213:Indomethacin