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A radioligand binding technique was used to study beta-adrenergic binding sites on rodent Leydig cells. Beta-Adrenergic binding sites were found on Leydig cells in both the rat and mouse. Binding of [3H]CGP-12177 [4-(3-t-butylamino-2-hydroxypropoxy)-[5,7-3H]benzimidazole-2-one] to purified rat Leydig cells was found to be saturable, temperature and time dependent, stereospecific, and readily reversible by the beta-adrenergic antagonist propranolol. Scatchard analysis revealed the presence of high-affinity sites with an apparent dissociation constant (Kd) of 0.79 +/- 0.22 nM and maximal binding capacity (Bmax) of 1716 +/- 245 sites per rat Leydig cell. Competition of various beta-adrenergic agonists and antagonists with [3H]CGP indicates an order of potency of L-isoproterenol greater than epinephrine = salbutamol greater than norepinephrine greater than D-isoproterenol and dl-propranolol = ICI 118,551 much greater than atenolol, respectively. These observations suggest that the binding sites are predominantly of the beta 2-receptor subtype. Incubation of freshly isolated rat Leydig cells with luteinizing hormone (100 ng/ml) caused consistent stimulation of androgen production, but only occasional stimulation by the beta-agonist isoproterenol (10 microM) was observed. However, these cells consistently responded to the beta-agonist after 3 h in primary cultures. These findings indicate that rodent Leydig cells possess beta-adrenergic binding sites and point out a possible dissociation between receptor recognition and physiologic response.

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The relation between involvement in aggressive interactions and a physiological index of stress was examined in a captive timber wolf pack (Canis lupus). Urine samples from known individuals were collected from snow throughout the mating season and analyzed for levels of the stress responsive hormone cortisol. When expressed relative to creatinine concentrations in the sample (thereby correcting for differences in urine concentration and dilution in snow), individual differences in urinary cortisol levels were found. These differences were consistent with behavioural data on aggression collected during the same period. Although males engaged in intrasexual aggression more frequently, female aggression was more serious in that females were more likely to be the targets of group chases and attacks. The dominant and only breeding female also aggressed against the two highest ranking males during courtship and mating contexts. The lowest ranking female had a significantly higher cortiso1:creatinine (C:C) ratio than all other females, and the second-ranking (beta) and most aggressive male, whose social position was unstable, had significantly higher C:C ratios than most other males. The data also suggest that urinary C:C ratios increase during the mating season for at least some individuals and vary in response to acute social stressors. The C:C ratios presented are similar to those reported from the urine of domestic dogs and a small sample of wild wolves, suggesting that these data from captive animals are not unusual. Comparisons with literature on primates and potential applications of these techniques are briefly discussed.RCsumC : Nous avons examine la relation entre les interactions agressives et un indice physiologique du stress au sein d'une meute de Loups gris (Canis lupus) en captivitC. Des Cchantillons d'urine d'individus connus ont Ct C recueillis dans la neige pendant toute la saison des accouplements et le cortisol, l'hormone de reaction au stress, y a Ct C dosC. ExprimCes par rapport aux concentrations de crCatinine dans 1'Cchantillon (compensant ainsi les diffirences de concentration de l'urine et sa dilution dans la neige), les concentrations de cortisol dans l'urine se sont avCrCes variables d'un individu a l'autre. Ces differences corresponsaient aux donnCes sur l'agressivitk recueillies au cours de la meme pCriode. Les miles s'attaquaient souvent a d'autres miles, mais, chez les femelles, les agressions Ctaient plus dangereuses puisque les femelles risquaient plus d'etre poursuivies et attaqukes par des groupes d'individus. La femelle dominante, la seule femelle a se reproduire, s'est attaquCe aux deux miles les plus dominants durant la pCriode de cours et durant la phase des accouplements. Chez la femelle la plus basse dans 1'Cchelle de dominance, le rapport cortisol : crCatinine (C : C) Ctait plus ClevC que chez toutes les autres femelles; chez le second mile parmi les plus dominants et les plus agressifs (beta), mile dont la position sociale Ctait instable, le rapport C : C Ctait Cgalement plus...