Effects of Acute Neurotrophic Stress on Peripheral Metabolism of Cortisol in Conscious Male Guinea-Pigs

Abstract

Cortisol metabolism was studied in conscious adult male guinea-pigs subjected to a neurotrophic stress (immobilization and stimulation by light for 3 h). The disappearance curves of tracer quantities of [3H]cortisol were represented by a two-pool model. In stressed animals, there was marked increase in the mean plasma level of cortisol (184% of control value; P less than 0.001) and in the metabolic clearance rate (MCR; 17% of control value; 0.001 less than P less than 0.001). This rise in the MRC of plasma cortisol resulted from an increase in the mean total apparent volume of distribution (49%, P less than 0.001). The lack of significant differences in the slopes of the second exponential phase of the disappearance curves indicated that the stress did not significantly increase the half-lie of cortisol. The mean binding capacity of transcortin for cortisol (ST) was significantly higher in the animals which had been subjected to the neurotrophic stress than in the control guinea-pigs (0.02 less than P less than 0.05). However, ST values remained very low and accounted for the very high levels of free cortisol found after the stress. The results suggest that the raised concentrations of unbound cortisol found in the plasma of conscious adult male guinea-pigs in response to neurotrophic stress reflect a hypersecretion of corticosteroid.

The splanchnic removal of cortisol from plasma of anaesthetized adult guinea-pigs

“…All the values in this study must, of course, be related to a stress situation since plasma cortisol levels under anaesthesia are much higher (/)<0001) than those obtained in undisturbed conscious guinea-pigs (0-96 + 0-007 pmol/1). However, the plasma MCR of cortisol was similar to that found in stressed conscious guinea-pigs which also had similarly high cortisol levels (Manin & Delost, 1981). The percentage extraction of cortisol by the splanchnic area (13% in males, 9% in females) was comparable with that measured in normal (8%) and adrenocorticotrophin-treated men (17%) by Zipser, Speckart, Zia, Edmiston, Lau & Horton (1976), but very low compared with anaesthetized (73%) and conscious sheep (58%) (Paterson & Harrison, 1972) or anaesthetized dogs (52%) (McCormick, Herman, Lien & Egdahl, 1974).…”

“…Nevertheless, the contribution of the splanchnic area to the total catabolism of cortisol is lower than that in the anaesthetized sheep (Paterson & Harrison, 1972) or dog (60%) (McCormick et al 1974). This is odd since the binding capacity of plasma proteins for cortisol is low in the adult male guinea-pig (Manin & Delost, 1981) and higher values for splanchnic extraction might have been expected. Perhaps in our experimental conditions the splanchnic uptake of cortisol from plasma is limited by the metabolism of cortisol in the liver.…”

Enhanced corticosterone-binding capacity in plasma after stimulation of the rat adrenal cortex: the possibility of a simultaneous release of protein and corticosterone

“…This finding is in agreement with that of Manin & Delost (1981) who found that the mean binding capacity of transcortin for cortisol in guinea-pigs was signifi¬ cantly higher in animals which had been subjected to neurotrophic stress.…”

Influence of Lesions in the Limbic-Hypothalamic System on Adrenocortical Responses to Daily Repeated Exposures to Immobilization Stress in Rabbits

“…However, the adrenocorticoid levels in blood of systemic circulation were decided by the balances between the rates of adrenocorticoid formation in adrenals and the metabolic rates of adrenocorticoids in other tissues. In fact, it was reported that the metabolic rates of adrenocorticoids were altered by the immobilization stress and other stresses and by the brain lesions in various animals (Kawakami et al, 1971;Few, 1974;Mode et al, 1980;Manin and Delost, 1981;Higuchi et al, 1981). Therefore, it was suggested that the adrenocorticoid levels in blood of systemic circulation were not the accurate indicators of adrenocortical responses to stress in animals with brain lesions.…”