EFFECTS OF AGE AND FOOD RESTRICTION ON CALCIUM SIGNALING IN PAROTID ACINAR-CELLS OF FISCHER-344 RATS

In this study, we characterized alpha-adrenergic (alpha AR) and muscar inic induced [Ca2+]i changes in individual parotid acinar cells from m ale Fischer 344 rats (6-24 month-old) fed ad libitum (AL) or 60% ad li bitum intake (FR). Cells were prepared by collagenase/hyaluronidase di gestion. [Ca2+]i teas measured by video image, fluorescent microscopy in single acinar cells loaded with FURA2. Neither age nor food restric tion altered the peak [Ca2+]i achieved in response to carbachol (100 m u M). Similar results were obtained for epinephrine (Epi=100 mu M) sti mulation in 6- and le-month-old animals. However, the peak [Ca2+]i res ponse to Epi declined between 12 and 18 months in both dietary groups (e.g., AL: 12 months=387+/-21 nM, 18 months=253+/-10 nM FR: 12 months= 430+/-22 nM, 18 months=325+/-14 nM). The decline in response to Epi se en with age was less in FR than in AL animals at 18 months, but not at 24 months. In addition, db cAMP reduced the carbachol-stimulated [Ca2 +]i response to levels comparable to those observed with epinephrine. The results support the view that calcium mobilization in parotid acin ar cells from male Fischer 344 rats in response to alpha AR, but not t o muscarinic, stimulation is impaired with age. Food restriction may s low down, but does not prevent, the functional decline. Furthermore, c AMP appears to modulate the muscarinic response. (C) 1997, Editrice Ku rtis.