Abstract
The CYP4A enzymes catalyze the formation of 20-hydroxyeicosatetraenoic acid (20-HETE), which has potent effects on the renal vasculature and tubular ion transport. Based on an increased 20-HETE formation in renal microsomes from spontaneously hypertensive rats, it has been proposed that increased expression of the CYP4A genes is an early event in the development of hypertension in these animals. To test this hypothesis, we developed RNase protection assays for specific detection of the individual CYP4A genes in the kidneys of spontaneously hypertensive and Wistar-Kyoto rats. Distinct age-dependent patterns of expression were observed for the individual CYP4A genes, with only CYP4A3 mRNA measurable in the kidneys of 1-week-old rats. CYP4A1 and CYP4A8 mRNA were detectable by 3 weeks of age and CYP4A2 mRNA at 5 weeks of age. The expression of CYP4A1 and CYP4A3 varied 4-5-fold throughout development and was highest between 3 and 5 weeks of age, declining steadily thereafter to 20% of their maximal level by 9 weeks of age. CYP4A2 mRNA levels increased steadily between 5 and 9 weeks of age, whereas CYP4A8 mRNA levels were relatively constant throughout development. The CYP4A3 mRNA level was significantly increased 1. 6-2-fold in the cortex and outer medulla of 1-4-week-old spontaneously hypertensive rat kidneys relative to the corresponding level in the Wistar-Kyoto. A similar 1.4-1.7-fold increase in CYP4A8 mRNA was also found in 3- and 4-week-old spontaneously hypertensive kidneys. Accompanying the increased expression of CYP4A3 and CYP4A8 mRNA in the prehypertensive rats were corresponding changes in functional CYP4A measured as either arachidonic acid or lauric acid omega-hydroxylase activity (1.4-2.0-fold increases) and CYP4A protein levels. After 4 weeks of age, the level of CYP4A mRNA, enzyme activity, and protein were similar in the kidneys of Wistar-Kyoto and spontaneously hypertensive rats. The findings suggest that the expression of CYP4A3 and CYP4A8 may be critical to the early changes in eicosanoid formation and renal function in the young spontaneously hypertensive rat.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.