AGE-RELATED-CHANGES IN RENAL CYTOCHROME-P-450 ARACHIDONIC-ACID METABOLISM IN SPONTANEOUSLY HYPERTENSIVE RATS

We recently demonstrated that renal synthesis of cytochrome P-450-dependent arachidonic acid (AA) metabolites is increased in spontaneously hypertensive rats (SHR) during the rapid elevation of blood pressure. In this study, the chemical identity of these metabolites is described, and the structural analysis together with differential susceptibility to antibodies suggested that they are derived from at least two different cytochrome P-450 isozymes: 1) the epoxygenase that metabolizes AA mainly to 11,12-epoxyeicosatrienoic acid (EET), which is further hydrolyzed to 11,12-dihydroxyeicosatrienoic acid (DHT) and 2) omega/omega-1 hydroxylase(s) that generate the 20-hydroxyeicosatetraenoic acid (HETE) and 19-HETE, respectively. Their production and release from the isolated kidney was activated by arginine vasopressin and inhibited by cytochrome P-450 enzyme inhibitors. The formation of these metabolites in SHR or WKY cortical microsomes was age dependent. The production rates of EET, DHT, and 19-HETE increased from fetal to 9 wk of age by 3-, 6- and 4-fold, respectively, whereas that of 20-HETE increased by 27-fold. The omega/omega-1 hydroxylase activities were significantly higher in SHR, whereas epoxygenase activity (sum of EET and DHT production) demonstrated no differences between the two strains at any age group tested, although the amount of EET vs. DHT in a given age was significantly different. Since these metabolites have a wide and contrasting spectrum of biological and renal effects (vasodilation and vasoconstriction, inhibition and stimulation of Na+-K+-ATPase), their relative production rates at a given age may influence not only renal hemodynamics and salt and water balance but also pro- and antihypertensive mechanisms in SHR.