Time course of apoptosis in small resistance arteries of spontaneously hypertensive rats

Objective The time course of programmed cell death (apoptosis) in the vascu lature of spontaneously hypertensive rats (SHRs) is still unclear, Moreover , no data are presently available about the possible interrelationships bet ween apoptosis and vascular remodelling. The aim of this study was to inves tigate the mesenteric small resistance arteries and large arteries (aortas) of SHRs and normotensive Wistar-Kyoto (WKY) rats at different ages, before and after the development of overt hypertension. Methods Twenty-tour SHRs (4, 8 or 12 weeks old) and 24 age-matched WKY rats were included in the study. Blood pressure was measured non-invasively. Ra ts were killed by decapitation and segments of aortas and small mesenteric arteries were dissected free from the surrounding tissue. Mesenteric arteri es were mounted on a micromyograph and structural characteristics were meas ured (media thickness, media:lumen ratio, etc.). Apoptotic cells in the tun ica media of large and small vessels were then stained using modified TdT-m ediated dUTP Nick-End Labeling (TUNEL), Results At 4 weeks of age no difference in the blood pressure and percentag e of apoptosis in mesenteric arteries between SHRs and WKY rats was detecte d; however, the media:lumen ratio of mesenteric small resistance arteries w as significantly greater in SHRs. At 8 and 12 weeks of age systolic blood p ressure, media:lumen ratio and apoptosis rate in mesenteric small arteries was significantly higher in SHRs. The rate of apoptosis in the aortas was s imilar in the two strains at all three ages. Conclusions An increased prevalence of apoptosis was observed in mesenteric small arteries of 8- and 12-week-old SHRs. It is possible that apoptosis m ay exert a role in small resistance artery remodelling during the developme nt and establishment of hypertension, J Hypertens 2000, 18:885-891 (C) Lipp incott Williams & Wilkins.