DELAYED RECOVERY OF LYMPHOCYTE BETA-ADRENOCEPTORS IN THYROIDECTOMIZED AGING PATIENTS

We previously found that the beta-adrenoceptor (beta AR) density of lymphocytes from thyroidectomized adult women shows a significant decrease early after surgery, followed by a slower recovery kinetics. In the present article, we posed the question whether the kinetics of lymphocyte beta ARs from thyroidectomized patients could be dependent upon the age of the donors. Thus, postsurgical decrease and the following recovery of beta AR density were studied in thyroidectomized female patients of different ages, along with the time course of triiodothyronine (T-3) and thyroxine (T-4) levels. The kinetics were analyzed using a mathematical model fitting experimental data. Results show that parallel statistically significant falls in beta AR density and T-3 levels are present in every age group tested from 1 to 3 days following surgical intervention. No statistically significant changes have been observed in T-4 levels. The recovery of beta AR density shows progressively slower kinetics with increasing patient age. In particular, a parameter estimating the time required to regain 50% of the fall in beta AR density increases exponentially with advancing age. T-3 levels show a recovery trend quite similar to that of beta AR density, but the kinetics is slower and does not present any statistically significant age-related changes. The kinetics of T-4 levels are completely different, showing a continuous slowly decreasing trend. Thus, the beta AR fall can be accounted for only by a decrease in T-3 levels. On the contrary, the comparison of T-3 and beta AR kinetics suggests that receptor recovery is also mediated by other regulatory factors. T-4 levels do not appear to have any direct role in both fall and recovery of beta ARs.