| Abstract: | The rate of arachidonic acid metabolism by prostaglandin (PG) endoperoxide synthetase by the rabbit renal cortex (approximately 200 pmol/mg of protein/min) is very slow compared to medulla (approximately 2000 pmol/mg/min). However, by using PGH2 as a substrate and limiting reaction times, we were able to directly measure the endoperoxide-dependent PGE2 isomerase and found that both the cortex and medulla possess high levels of this activity (approximately pmol/mg/min). The PG endoperoxide E2 isomerase is dependent on reduced glutathione, but not cysteine, and is inactivated by p-hydroxymercuribenzoate or boiling. Thus, the renal medulla appears to exhibit an efficient coupling of cyclooxygenase and PG endoperoxide E2 isomerase, whereas the cortex has a vast excess of endoperoxide-dependent enzyme. |
