1-¹⁴C-ARACHIDONIC ACID INCORPORATION INTO THE LIPIDS OF RAT AORTA.EFFECT OF EXHAUSTION ON PGI2 PRODUCTION

 

PDF Download Permissions and Reprints

Prostacyclin (PGI2) production in rat aortic rings incubated in Tris-buffer decreases with time.It has been shown that this decrease is not dependent on the total arachidonate concentration in the arterial lipids, and it has been suggested that it may be due to a partial enzymatic inactivation of cyclooxygenase and / or PGI2-synthethase. However, there is a possibility that although the total l-¹⁴C-arachidonate (AA*) incorporation increases with exhaustion, this incorporation into the different lipid fractions may be different before and after the exhaustion process.In this study we evaluate this possibility by assessing the incorporation of AA* into rat aorta lipids in control samples and after 180 min exhaustion in 10mM Tris-buffer saline pH=7.4 or human plasma. In addition 6-keto-PGFl (6K) formation from endogenous AA was also evaluated in^α the above mentioned experimental conditions by RIA. The results show that this 6K production is drastically reduced by the exhaustion in Tris-buffer (91%) and to a lower extent in arteries exhausted in plasma (52%). With regard to AA* incorporation into the total lipid fractions, it was found that in control arteries 67% was incorporated in phospholipids (PL),19% in triglycerides (TG) and 4.2% in esterified cholesterol. The AA* incorporation into the different PL was: 31% in phosphatidyl-choline (PC), 28% in P-ethanolamine (PE), 25% in P-serine+P-inositol, 8% sphingomyeline and 6% lisolecitine.When the arteries are exhausted in Tris-buffer the AA* incorporation decreases in TG and increases in total PL when compared to control samples. Additionally, a very significant increase of AA* in PE and a decrease in PC were found. In plasma-exhausted sairples the AA* incorporation into the arterial lipids shows the same trend as in Tris-buffer exhausted samples, although these differences were lower in the former when compared to the control. When rat aortic rings are exhausted in Tris-buffer there is a remarkable reduction in PGI2 production and an alteration in the AA* incorporation into the arterial lipids.Plasma has a protective effect on rat aorta during the exhaustion process.