Impact of cortisol on α-actin content in vascular smooth muscle cells of fetal sheep

Abstract

1. The effects of gestation on α-actin levels in vascular smooth muscle aortae were studied in 31 fetal sheep, aged 66-144 days (term = 150 days). Aortae were collected post-mortem. 2. Aortae, carotid and femoral arteries from two groups of chronically catheterized fetal sheep (110-114 days) were also examined. One group was infused with cortisol (n = 6; hydrocortisone sodium succinate, total dose 16.8 mg in 48 h) and the control group received saline (0.15 mol/L, 0.33 mL/h, n = 7). 3. Vascular homogenate protein was separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and western transfer. α-Actin was identified using a monoclonal mouse anti-α actin antibody and standardized against tissue protein and DNA content. 4. Between 60 and 144 days gestation, there was an exponential increase in the α-actin content of vascular smooth muscle cells from fetal sheep aorta (P < 0.0001). α-Actin concentration (densitometry units (U) relative to DNA 260 nm absorbance (Abs)) was significantly (P < 0.05) higher in the aortae of cortisol-infused (12 601 ± 2499 U/Abs) fetal sheep compared with those that were saline-infused (4514 ± 670 U/Abs). α-Actin (relative to DNA absorbance) of carotid and femoral vessels in cortisol-infused animals (20 659 ± 4812 U/Abs) compared with those that were saline-infused (14 461 ± 2645 U/Abs) was increased, but the difference was not significant. 5. Therefore, the α-actin concentration of the vascular smooth muscle of the aorta increases throughout gestation. Cortisol treatment is associated with further increases in α-actin concentration in the fetal aorta, indicating that the development of large conduit vessels can be altered by this glucocorticoid. © 2006 Blackwell Publishing Asia Pty Ltd.