Insulin receptors in mouse brain: Reversibility of age-related impairmentsby a thymic extract

Recently, we have shown that insulin receptors (InsRs) in the brain undergo impairments with aging. Interestingly, age-related alterations of brain In sRs, are not irreparable as thymus grafts are able to recover them. With th e present study we verified the possibility that an aqueous extract from ca lf thymus (TME) can mimic the restoring action of age-related impairments i nduced by thymus graft. InsR characteristics were assayed in a group of 25 months old BALB/c-nu mice treated with TME: 2 mug/g body weight every third day, for total five subcutaneous injections. The last dose was injected th e day before animals were killed. Other two groups of young (4 months) and old (25 months) mice received saline solution with the same schedule. A two -sites model analysis of receptor data confirms the age-dependent decrease of InsR number and k(d) previously observed in the high affinity population . Furthermore, a statistically significant recovery of number impairment is shown in TME-treated animals. On the contrary, the characteristics of the low affinity receptor subset show no statistically significant differences among the three animal models studied. TME induced recovery of the age-rela ted changes found in brain InsRs, together with previously observed regulat ory action of the same thymic extract on the adrenergic system, suggest tha t thymic gland does not necessarily have to mutually interact with other co ntrolling systems for maintaining or recoving homeostasis of the complex ne uroendocrine network during development and aging.