Strain differences in urinary hydroxycorticosteroids in guinea pigs

Abstract

Because of previously noted variations in the urinary excretion of corticosteroids when guinea pigs of different genetic background were utilized in various experimentally induced pathological conditions, a study of the daily excretion of three unconjugated, polar corticosteroids (6ß hydroxycortisol, 2α hydroxycortisol and cortisol) was undertaken over a 24-day period in noninbred (Hartley albino) as well as inbred (strain 2 and strain 13) guinea pigs, prior to and immediately following the administration of 10 u of ACTH using established methods. Prior to ACTH treatment the summed daily excretion of these three free corticosteroids was 40γ, 63γ and 48γ, while following ACTH the excretion was 285γ, 238γ and 166γ for Hartley, strain 2 and strain 13 animals, respectively. Prior to ACTH treatment the major corticosteroid excreted by all three animal groups (10 to a group) was 2α hydroxycortisol. Following ACTH the major polar corticosteroid excreted by noninbred Hartley animals was cortisol while the major polar corticosteroid excreted by the inbred Strains was 2α hydroxycortisol. Although the excretion of 2α hydroxycortisol as the major free normal polar corticosteroid was unanticipated, the high production of cortisol in this species is well known and has been offered as partial explanation for successful hetero and homoiotransplantation in this species.