Diurnal variation in adrenal gland freshweight due to vascular damming: a possible role in corticosterone storage.
Previous in vitro studies have disclosed the existence of a diurnal variation in adrenal gland freshweight in the minimally stressed rat (inactive phase freshweight > active phase freshweight). In the present study this active/inactive phase difference in adrenal weight was examined using light microscopy, transmission electron microscopy (TEM) and backscattered scanning electron microscopy (BSEM). Morphological and stereological examination of the resultant micrographs has shown a significant increase in gland cross-sectional width in the active phase, localised to the zona fasciculata/reticularis region of the cortex. However, TEM examination of cells from this region, comparing volume and surface densities from active and inactive phase glands, has not provided evidence of a diurnal variation in cell size. Analysis of the BSEM investigation of vascular, cellular and interstitial compartments of the glands confirmed the absence of variation in the cellular compartment but showed a diurnal variation in the vascular compartment of the zona fasciculata/reticularis. The circadian related changes in vascular volume density begin at the cortico-medullary border where greatest difference is observed between the active and inactive phases. This difference continues throughout the zona fasciculata/reticularis decreasing in size as it approaches the zona glomerulosa region. These findings are explained in terms of the existence of a cortico-medullary vascular dam that is a possible contributor to the rapid steroidogenic response seen on initial stimulation of the gland by adrenocorticotrophic hormone (ACTH).
West
S H
SH
School of Biological Sciences, Macquarie University, NSW, Australia.
Bassett
J R
JR
D000311:Adrenal Glands / Q000033:anatomy & histology* / Q000098:blood supply / Q000378:metabolism; D000818:Animals; D002452:Cell Count; D002940:Circadian Rhythm / Q000502:physiology*; D003345:Corticosterone / Q000378:metabolism*; D008297:Male; D009929:Organ Size / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
D003345:Corticosterone