Adrenoceptor coupling mechanisms which regulate salivary secretion during aging.

In parotid slices and membranes from Wistar rats 2, 12 and 24 months old, changes are noted in adrenoceptor-stimulated K+ fluxes, formation of [3H]inositol phosphates ([3H]IPs), cAMP production, and membrane environment. Norepinephrine-stimulated K+ efflux and formation of [3H]IPs in the slices proceed through an alpha 1-adrenergic mechanism and are reduced 20% and 40% during aging, respectively. In beta-adrenoceptor stimulation with isoproterenol, no age changes were observed in K+ influx and cAMP production. The cholesterol content in membranes was reduced with age; concomitantly, the membrane viscosity decreased with age. These results indicate that the alterations in the membrane environment may provide age-dependent modulation of alpha 1-adrenoceptor coupling mechanisms and their functions.