INOSITOL PHOSPHATES AND INTRACELLULAR CALCIUM AFTER BRADYKININ STIMULATION IN FIBROBLASTS FROM YOUNG, NORMAL AGED AND ALZHEIMER DONORS

Several studies suggest that alterations in the receptor-mediated phosphoinositide cascade and cytosolic free calcium concentration ([Ca2+]i) are involved in the pathophysiology of aging and Alzheimer's disease. Therefore, the phosphoinositide cascade and [Ca2+]i were determined under resting conditions and after stimulation with bradykinn (100 nM) in cultured human skin fibroblasts from young (21 +/- 3 years), normal aged (59 +/- 6 years) and Alzheimer subjects (58 +/- 6 years). The inositol polyphosphates (IP3, IP2 and IP) were monitored after prelabeling the cells with [H-3]inositol in serum free medium. [Ca2+]i was determined with the fluorescent probe, fura-2AM, under exactly analogous conditions. The bradykinin-induced formation of IP3 and IP2 increased significantly in fibroblasts from normal aged and Alzheimer donors compared to young subjects, but did not differ from each other. Bradykinin-induced IP3 formation was 63-117% above the young group at time points between 10-60 s in normal aged or Alzheimer donors. Bradykinin-induced IP2 formation was 49-59% above the young group at time points between 10-60 s in normal aged or Alzheimer subjects. Neither the basal [Ca2+]i, nor the bradykinin-stimulated [Ca2+]i, differed among fibroblasts from young, normal aged and Alzheimer donors. The precise molecular basis and pathophysiological significance of the enhanced bradykinin-induced phosphoinositide cascade in fibroblasts from aged donors remains to be determined.