Corticoid concentrations are increased in the plasma and urine of ewes with naturally occurring scrapie.

ABSTRACT

The 24-h pattern of corticoid plasma concentrations was determined in scrapie-affected ewes during the clinical phase of the disease. Twenty one ewes (8 healthy and 13 scrapie-affected ewes) were subjected to 24-h blood sampling sessions. Urine samples were simultaneously obtained during the clinical stage of the disease and in healthy ewes. The scrapie diagnosis was performed by histopathology. Plasma and urinary corticoids were assayed using HPLC methods. Mean plasma and urinary levels of corticoid (cortisol, 20beta-dihydrocortisol cortisone) of scrapie-affected ewes were greater than those observed in healthy ewes. 20Beta-dihydrocortisol appeared to be the main cortisol metabolite in ewes. The intra-individual variations of 20beta-dihydrocortisol plasma concentrations were lower than the corresponding plasma cortisol concentrations due to the dampening effect of the metabolic process on the short term variations of cortisol secretion. This dampening mechanism was amplified in urine, the urinary concentrations integrating cortisol production over the period preceding sampling. For these reasons, 20beta-dihydrocortisol could present a potential interest for a non invasive diagnostic test of transmissible spongiform encephalopathies. The pathophysiological consequences of an excessive exposure to cortisol on development of the neurogenerative process are discussed.