Analysis of the renin gene intron A tandem repeat region of Milan and Lyon hypertensive rat strains.

The region of intron A of the rat renin gene containing a unique tandemly repeated sequence was analysed in the Milan and Lyon hypertensive rat strains and their controls, and in several Sprague-Dawley rats, using an oligonucleotide probe complementary to the tandemly repeated sequence and a renin complementary DNA probe. In the Milan rats, the size of the Bgl II DNA fragment encompassing the tandem repeat region was the same in the hypertensive (MHS) and normotensive (MNS) strains. In the Lyon model, a difference of 1.1 kilobase (equivalent to about 28 copies of the 38 basepair tandem repeat sequence) was observed in the size of the Bgl II fragment of the hypertensive (LH) and normotensive (LN) strains. However, the finding that the size of the fragment in the Lyon low-blood-pressure (LL) strain was the same as that in the LH strain rather than the LN strain suggests that the difference between the two latter strains is not by itself a major cause of the blood pressure difference between them in the intron A tandem region. An analysis of Sprague-Dawley rats, from which the Lyon strains are derived, showed that at least three different renin gene alleles, two with Bgl II fragments of the same size as those seen in the Lyon strains, are randomly segregating in this population.