Female Wistar-Kyoto and SHR/y rats have the same genotype but different patterns of expression of renin and angiotensinogen genes.

OBJECTIVES

To evaluate whether renin and angiotensinogen gene expression in females from two strains of rats that share the same autosomes and X chromosomes differs. Female SHR/y rats have the parental Wistar-Kyoto rat autosomes and X chromosomes and have no chromosomes of spontaneously hypertensive rat origin; thus they are genetically equivalent to female Wistar-Kyoto rats.

DESIGN AND METHODS

Because these genes are regulated by steroid hormones, we investigated the effects of removal of estrogen (ovariectomy) and addition of androgen (testosterone implants) on three groups of female SHR/y rats and the parental rat strain Wistar-Kyoto rat with groups of intact (control) rats, rats subjected to ovariectomy at age 3 weeks, and rats subjected to ovariectomy with a testosterone implant at age 3 weeks.

RESULTS

The combination of removing estrogen early in development and supplementing the ovariectomized females with testosterone revealed strain differences in response of blood pressure. Renin and angiotensinogen messenger RNA levels appear to be regulated coordinately within each strain, although actual levels of messenger RNA differ between the strains.

CONCLUSIONS

Similar patterns of responses of renin and angiotensinogen genes to ovariectomy and ovariectomy plus testosterone suggest that regulation of the genes is likely to be similar or coordinate. Differences in regulation of renin-angiotensin system genes between strains may result from epigenetic mechanisms such as genome imprinting of these genes or of another gene that functions as a common regulator of renin and angiotensinogen.