To determine whether decreased perfusion pressure affects the abundance and distribution of renin and its mRNA and the expression of the angiotensin II type 1 (AT1) receptor gene within the kidney, adult male Sprague-Dawley rats were subjected to aortic coarctation proximal to the renal arteries (Coarc, n = 8) and compared with sham-operated rats (Sham, n = 6). Renal renin distribution was determined by immunocytochemistry using a specific polyclonal antibody against rat renin. Renin mRNA was assessed by in situ hybridization to a 35S-labeled oligonucleotide complementary to rat renin mRNA. Kidney AT1 mRNA levels were determined by Northern analysis using a 1,133-base pair rat AT1 cDNA. Femoral arterial blood pressure, measured 24 h after surgery, was lower in Coarc than in Sham rats (75 +/- 5.4 vs. 122 +/- 2.3 mmHg, P < 0.05). Aortic coarctation increased the percent of juxtaglomerular apparatuses (%JGA) containing renin and its mRNA (85 +/- 2.5 and 66 +/- 2.8 vs. 49 +/- 5.3 and 36 +/- 1.7%, Coarc vs. Sham, P < 0.05) and the intensity of hybridization signals (497 +/- 89 vs. 71 +/- 12 grains/JGA, Coarc vs. Sham, P < 0.05). In addition, recruitment of renin gene expressing cells was observed along afferent arterioles in Coarc rats, whereas renin and its mRNA were limited to the JGAs in Sham rats. Renal AT1 receptor gene expression was threefold lower in Coarc than in Sham rats. We conclude that reduction of perfusion pressure after abdominal aortic coarctation acutely enhances renin gene expression and downregulates AT1 receptor gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)