Effects of age and food restriction on calcium signaling in parotid acinar cells of Fischer 344 rats.

Abstract

In this study, we characterized alpha-adrenergic (alpha AR) and muscarinic induced [Ca2+]i changes in individual parotid acinar cells from male Fischer 344 rats (6-24 month-old) fed ad libitum (AL) or 60% ad libitum intake (FR). Cells were prepared by collagenase/hyaluronidase digestion. [Ca2+]i was measured by video image, fluorescent microscopy in single acinar cells loaded with FURA2. Neither age nor food restriction altered the peak [Ca2+]i achieved in response to carbachol (100 microM). Similar results were obtained for epinephrine (Epi = 100 microM) stimulation in 6- and 12-month-old animals. However, the peak [Ca2+]i response 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 seen 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 acinar cells from male Fischer 344 rats in response to alpha AR, but not to muscarinic, stimulation is impaired with age. Food restriction may slow down, but does not prevent, the functional decline. Furthermore, cAMP appears to modulate the muscarinic response.