| Abstract: | In an attempt to further investigate circadian changes in kidney function, the planar surface area (PSA) (µm 2) of renal isolated glomeruli from normal rats was monitored using a computerized image analyzer method. Eight male Sprague-Dawley (SPRD) rats, aged 12û14 weeks, were entrained to a 12-h light/12-h dark cycle in controlled environmental conditions of temperature (22±2°C) two weeks before the experiments started. Isolated glomerular preparations were obtained, using a mechanical sieving technique, at four different circadian times: 07:00, 13:00, 19:00 and 01:00. It was the finding of the present study that the PSA of the glomeruli varied significantly over the 24-h period, but showed a weak amplitude. The size of the glomeruli reached the highest values at night (21358.59±456.72 µm 2 at 21:17) with an acrophase at 21:39, as do all the other renal parameters, but also blood pressure and many vasoactive compounds involved in the regulation of the mesangial cell physiology, contractile element of the glomerulus. Such chronobiological data not only provided a clear example of complementarity between in vivo and ex vivo experiments, but evidenced that temporal changes do exist in kidney structure and could be correlated with rhythms in renal physiology. |
