It is known that inbred Dahl salt-sensitive (S) rats carry a different renin allele than inbred Dahl salt-resistant (R) rats. The levels of, and responses of, renal renin and renal renin mRNA to sodium deficient diet and to sodium deficient diet plus Captopril treatment were compared in S and R rats. S rats had lower renal renin and lower renal renin mRNA than R rats on control (1% NaCl) diet. Sodium deficient diet caused a modest increase, and sodium deficient diet plus Captopril caused a very large increase in both renal renin and renal renin mRNA in both strains. In general, both S and R strains appeared to regulate renin similarly in response to provocative stimuli.