Male-female differences in the impact of beta-adrenoceptor stimulation on resistance to experimental metastasis: Exploring the effects of age and gonadal hormone involvement

We studied the development of sexual dimorphism in resistance to NK-sensitive experimental metastasis under baseline conditions and following adrenoceptor stimulation. With increasing age, baseline resistance to MADB 106 lung tumor retention (LTR) increased in both sexes, but also the susceptibility to the tumor-enhancing effects of a beta-adrenergic agonist, metaproterenol. Beginning at 13 weeks, males exhibited a 2- to 3-fold greater increase in LTR than females following adrenoceptor stimulation. This adult dimorphism was robust to ovariectomy, and questionably related to androgens. The findings are consistent with reduced female responsiveness to sympathetic activation, and substantiate the importance of including both sexes when studying neuroimmunomodulation. (C) 2007 Elsevier B.V. All rights reserved.