Regional histomorphometry and distribution of Androgen receptor in the common carotid arteries among Kenyans
Background: The carotid intimomedial thickness is a predictor of atherosclerosis in other vascular beds and is useful in cardiovascular risk stratification. Atherosclerosis is reported to be worse in males and seems to increase with age. There have been reports that androgens are protective while other reports suggest they are bane. Expression distribution of androgen receptors in the carotid intimomedial thickness may help explain the role of androgens in development and progression of atherosclerosis. The relationship between the androgen receptors and the carotid intimomedial thickness is unknown. Hypothesis: There are segmental, age and gender differences in the carotid intimomedial thickness which are influenced by presence of androgen receptors. Objectives: To describe the distribution of androgen receptors in the common carotid artery intima and media and relate them with the carotid intimomedial thickness among Kenyans. Study design: Descriptive crossectional study Setting: Department of Human Anatomy, University of Nairobi. Materials and Methods: Materials for this study were obtained from twelve (6 males and 6 females) common carotid arteries during autopsy within 48 hours of demise at the Chiromo funeral parlour. Three millimetre samples from the proximal, middle and distal thirds of artery segments were collected. They were fixed in 10% formaldehyde solution immediately and routinely processed for light microscopy. Another set of slides were stained using antiandrogen receptor monoclonal antibody (AR 318). All prostate samples used as positive controls were immunopositive for androgen receptors. The total cell count and the number of stained cells for each designated vessel zone were assessed in the three sections in four visual fields per section at 400 x magnification using a Zeissﾮ photomicroscope. The carotid intimomedial thickness was measured. The presence and distribution of androgen receptors were observed and described. The intimomedial thickness was measured using the Scion Image Multiscanﾮ software. The data collected was analysed using SPSSﾮ version IS for Windowsﾮ for means and variances. Results: The mean age of the cases was 2Sﾱ19yrs. Mean carotid intimomedial thickness was O.S6ﾱO.22 mm (Male: 0.97ﾱ0.22; Females 0.77ﾱ0.06), p=0.05. Mean proximal, middle and distal intimomedial thickness were 0.S6+0.26 mm, 0.S4+0.2Smm and 0.90+0.35mm respectively. Carotid intimomedial thickness increased with age; 0.5ﾱO.l6mm, 0.S7ﾱ0.24mm and 1.21ﾱ0.36 mm for the age groups 0-20yrs, 21-40yrs and 41-60yrs respectively (p=0.035). Androgen receptors were not detected in the 12 samples tested. Conclusions: The common carotid artery is an elastic artery with a well-developed tunica intima and does not display androgen receptors. Carotid intimomedial thickness increases distally, with age and is higher in males. The carotid intimomedial thickness is not influenced by the presence of androgen receptors.