Diet restriction retards the age-related loss of beta-adrenergic receptors and adenylate cyclase activity in rat lung.

In the rat, dietary restriction prolongs life span and retards a variety of physiological processes that change with age. Beta-adrenergic responsiveness declines with age. We assessed beta-adrenergic receptor density and adenylate cyclase activity in lungs of 6-, 18-, 24-, and 27-month-old rats fed ad libitum or restricted to 60% of the ad libitum food after 6 weeks of age. Beta-adrenergic receptor density declined in the ad libitum group (M +/- SE, 417 +/- 30, 349 +/- 23, 297 +/- 19, 260 +/- 30 fmol/mg protein, p less than .01). In the diet-restricted group, beta-adrenergic receptor density declined between 6 and 18 months (493 +/- 35, 370 +/- 28, p less than .05) but remained unchanged from 18 to 27 months (370 +/- 28, 333 +/- 19, 360 +/- 16). Isoproterenol-stimulated adenylate cyclase activity declined with age in the ad libitum group (53.4 +/- 7.5, 46.8 +/- 8.8, 38 +/- 3.9, 27.8 +/- 3.3 p mol cAMP/mg protein, p less than .05) but not in diet-restricted group (45.1 +/- 8.9, 44 +/- 7.9, 41.8 +/- 2.4, 47.3 +/- 5.1). Changes in forskolin-stimulated adenylate cyclase activity with age were not affected by diet restriction. These data suggest that diet restriction retards some of the age-related changes in the beta-adrenergic pathway.