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Corticotropin-releasing factor (CRF) was bioassayed and arginine vasopressin (AVP) radioimmunoassayed from punched-out hypothalamic nuclei. The highest concentration of CRF was found in the median eminence (ME), followed by the paraventricular nucleus (PVN), supraoptic nucleus (SON), suprachiasmatic nucleus (SCN), arcuate nucleus (ARC), dorsomedial nucleus (DMN) and ventromedial nucleus (VMN). The AVP concentration was in the order of ME, SON, PVN, SCN, ARC, VMN and DMN. Sephadex G-25 gel filtration of the ME extracts showed one peak for AVP and two peaks for CRF. One CRF peak appeared on the void volume (big CRF) and the other (small CRF) was coeluted with AVP. Gel filtration of the PVN and SON extracts showed one peak for AVP but three or four peaks for CRF. The addition of anti-AVP serum (AVP-AS) to pituitary cell cultures reduced the CRF activities of AVP and ME extracts by approximately 80 and 40%, respectively. When the small CRF fraction of ME extracts was treated with AVP-AS on affinity chromatography, the unbound fraction (AVP-free) still showed significant CRF activity. Re-examination of CRF concentration using AVP-AS showed that it was still highest in ME, but was significantly higher in PVN than in SON, SCN and ARC. These results suggest that the PVN is an important nucleus for producing corticotropin-releasing hormone.

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We examined the effects of angiotensin–converting enzyme inhibitor (ACEI) and angiotensin II type 1 receptor antagonist (AT1a) on the action of protooncogene c–fos in salt–sensitive hypertensive rats. Seven–week old Dahl salt–sensitive rats fed a high (8%)–salt diet were treated with ACEI, cilazapril (10 mg/kg) or AT1a, TCV–116 (1mg/ kg) every day for 6 weeks. The control animals were fed a low (0.3%)–salt diet. Systolic blood pressure gradually increased in high–salt–loaded rats and was higher than low–salt–treated rats throughout the study. However, both medications had no significant antihypertensive effect. After 6 weeks of therapy, glomerular mRNA and nuclear protein were extracted from the resected kidneys. Competitive reverse transcription–polymerase chain reaction showed a high level of glomerular c–fos mRNA in high–salt–loaded rats and that ACEI or AT1a treatment did not significantly change its level. Electrophoretic mobility shift assay demonstrated that treatment with AT1a significantly decreased the activator protein–1 (AP–1) binding activity in the glomerular nuclear extract compared to ACEI. Our findings suggest that, compared with ACEI treatment, long–term treatment with AT1a may contribute to attenuation of the glomerular injury in salt–sensitive hypertension by inhibiting AP–1 transcription activity independent of its antihypertensive effect.