CHARACTERIZATION OF NEW INBRED STRAINS OF DAHL-IWAI SALT-SENSITIVE AND SALT-RESISTANT RATS

Dahl-Iwai salt-sensitive (S) and salt-resistant (R) rat strains were n ewly established as inbred strains. To characterize the strains, the D ahl-Iwai S and R rats were fed low-salt (0.3% NaCl) and high-salt (8.0 % NaCl) diets from 5 weeks after birth, and systolic blood pressure an d pathologic findings were examined at intervals. The distributions of alleles at 19 biochemical and immunologic loci also were examined in the aforementioned strains, together with those for the inbred SS/Sea and SR/Sea strains, which were derived from inbred SS/Jr and SR/Jr str ains, respectively. The Dahl-Iwai S rats were hypertensive after 3 wee ks of consuming the 8.0% NaCl diet and died from 6 to 10 weeks after t he diet was initiated. Renal lesions developed after 4 weeks' consumpt ion of the high-salt diet. The Dahl-Iwai S rats were not hypertensive until at least the age of 21 weeks while they comsumed the 0.3% NaCl d iet, whereas it was reported that the SS/Jr rats became hypertensive a t about 20 weeks of age when they consumed the low-salt diet. The Dahl -Iwai R rats were normotensive whether fed the 0.3 or 8.0% NaCl diet. Hydronephrosis was not observed in the Dahl-Iwai R rats, though it dev elops in SR/Jr rats with high frequency. Different distributions were detected for kidney alkaline phosphatase-l (Ahp-l) and amylase-l (Amy- 1) alleles between the Dahl-Iwai S and SS/Sea strains, and for esteras e-14 (Es-14) and seminal vesicle protein-1 (Svp-1) alleles between the Dahl-Iwai R and SR/Sea strains. The phenotypic differences between th e substrains of inbred Dahl rats could be ascribed to different geneti c backgrounds.