Hormonspiegel im Plasma und Enzymaktivitäten im Fettgewebe von Piétrain- und Edelschweinen1

Comparative determination of beta-adrenergic receptors in muscle, heart and backfat of Piétrain and Large White pigs

The number of beta-adrenergic receptors which influence the effectiveness of catecholamines was determined by 3H-dihydro-alprenolol in muscle, heart and fat tissue of stress-susceptible pigs (Pietrains) and non-susceptible pigs (Large Whites). In all investigated tissues proportionately 0·31 to 0·38 more receptors were found in the Pietrains than in the Large Whites, the differences being significant (P < 0·05). That the higher numbers of beta-adrenergic receptors in Pietrain pigs may be involved in accelerated muscle glycogenolysis (poor meat quality) and increased lipolysis (low carcass fat) in these animals and in other breds showing poor meat quality and low carcass fat is discussed.

Hypothalamo-pituitary-adrenocortical axis in stress-susceptible and stress-resistant pigs: endocrine responses to corticotrophin-releasing factor and vasopressin*

Swiss Landrace pigs selected into genetically well-characterized low and high tissue fat lines (f and F respectively) react differently to exogenous and endogenous stressors. Response of the hypothalamo-pituitary-adrenocortical (HPA) axis to i.v. administered ovine corticotrophin-releasing factor (oCRF) and lysine vasopressin (LVP) in young females, intact and pretreated with dexamethasone or metyrapone, leads to the conclusion that different stress susceptibility of the two lines correlates with the sensitivity of pituitary corticotrophs to oCRF stimulation. Total amount of ACTH released after stimulation with submaximal oCRF doses was roughly equal in both lines, and cortisol level is even lower in the f-line, most likely due to the considerably enhanced metabolic clearance rate of cortisol (lower half-life of plasma cortisol compared with F-line). LVP-stimulated ACTH release is comparable with that of oCRF is stronger in the f-line. Combined effect of oCRF and LVP is rather additive than synergistic but the half-life ratio cortisol/ACTH after this stimulation is about four times higher than for stimulation by LVP and oCRF separately. In cases of externally stimulated HPA axis, cortisol plasma concentration tightly cross-correlates with that of ACTH.