Interstrain differences in angiotensin I-converting enzyme mRNA and activity levels. Comparison between stroke-prone spontaneously hypertensive rats and Wistar-Kyoto rats.

Plasma angiotensin I-converting enzyme (ACE) levels are different between t he stroke-prone spontaneously hypertensive rat (SHRSPHD) and the normotensi ve Wistar-Kyoto (WKYHD) rat. This interstrain variability in plasma ACE lev els is independent of blood pressure and is genetically linked to the ACE g ene. The present study explored the hypothesis of an interstrain variabilit y of tissue ACE activity and ACE gene expression levels. Tissue ACE levels were studied by enzymic activity measurement in the membrane fraction, and ACE mRNA levels were quantified by solution hybridization-ribonuclease prot ection assay. In lung, heart, kidney, and duodenum, membrane-bound ACE acti vity and ACE mRNA amount were significantly higher in WKYHD rats compared w ith SHRSPHD rats. No difference was observed in the testis where a specific isoform of the enzyme is produced. Our results suggest that in addition to determine differential plasma ACE levels between the WKYHD and SHRSPHD str ains, the interstrain genetic variability also determines differential ACE mRNA and membrane-bound enzyme levels in somatic tissues. This likely refle cts a difference in the ACE gene expression due to genetically determined r egulatory mechanisms operative in all somatic tissues.