Telemetric blood pressure monitoring in benign 2-kidney, 1-clip renovascular hypertension: effect of chronic caffeine ingestion.
In the present study we used radiotelemetry technology to investigate: 1) the time course for development of hypertension in 2-kidney, 1-clip (2K1C) rats and 2) the effect of chronic caffeine consumption on blood pressure in 2K1C rats. Rats received water or caffeine (0.1%) in drinking water and were instrumented with radiotelemetry devices to permit continuous monitoring of blood pressure. A clip was placed on the left renal artery of rats in both the water (WATER/CLIP) and caffeine (CAFFEINE/CLIP) groups. The clip was applied briefly to, then removed from, the renal artery of caffeine- and water-treated rats randomized to the sham-operated (SHAM) group. Mean arterial blood pressure (MABP) increased by approximately 35 mm Hg within 2 hr of clipping. MABP in the WATER/CLIP and CAFFEINE/CLIP groups differed significantly from the SHAM group, but not from each other, for the first 10 days after clipping. Thereafter, MABP was greater in the CAFFEINE/CLIP rats as compared to WATER/CLIP rats. At 4.5 weeks after clipping, MABP values differed significantly in the CAFFEINE/CLIP, WATER/CLIP and SHAM rats (140 +/- 4, 122 +/- 4 and 103 +/- 2 mm Hg, respectively). Involvement of the renin-angiotensin system was assessed by treatment with the AT1 receptor antagonist, losartan, and the converting enzyme inhibitor, captopril. Results from this study indicate: 1) hypertension develops rapidly after clipping in rats monitored with telemetry; 2) the renin-angiotensin system is involved in maintaining hypertension in 2K1C rats even beyond 4 weeks after clipping; and 3) caffeine augments the increase of blood pressure in 2K1C rats, apparently through the involvement of the renin-angiotensin system.
Kost
C K
CK
Center for Clinical Pharmacology, University of Pittsburgh Medical Center, Pennsylvania.
Li
P
P
Pfeifer
C A
CA
Jackson
E K
EK
D000804:Angiotensin II / Q000037:antagonists & inhibitors; D000818:Animals; D001713:Biphenyl Compounds / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D002216:Captopril / Q000494:pharmacology; D003250:Constriction; D006339:Heart Rate / Q000187:drug effects; D006978:Hypertension, Renovascular / Q000139:chemically induced / Q000503:physiopathology*; D007093:Imidazoles / Q000494:pharmacology; D007668:Kidney / Q000502:physiology; D019808:Losartan; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012084:Renin-Angiotensin System / Q000187:drug effects / Q000502:physiology; D013686:Telemetry; D013777:Tetrazoles / Q000494:pharmacology
D001713:Biphenyl Compounds; D007093:Imidazoles; D013777:Tetrazoles; D000804:Angiotensin II; D002110:Caffeine; D002216:Captopril; D019808:Losartan