Optical and NMR Spectroscopy in the Study of Secretion

Abstract

The sequence of events in stimulus-secretion coupling in pancreatic acinar cell can be divided into three main steps; activation of receptors by proper stimuli, conduction of excitation, and extrusion of secretory substances. These three main steps occur in acinar cells in three functionally different cellular structures: The receptive portion is basiolateral membrane, and the output portion is the apical membrane. Following eceptor activation, intrtacellular processes, including an increase in cytosolic Ca²⁺, [Ca²⁺]_c,mediate exocytosis and Cl⁻ efflux at the apical membrane. Every step in stimulus-secretion coupling may utilize energy, the immediate source of which is ATP. There is evidence that mitochondria supply more than 90% of the energy needed by the pancreas (Bauduin et al., 1969). The dynamic change in the production and utilization of energy in the exocrine pancreas can be monitored noninvasively with the aid of optical and NMR spectroscopy in the isolated perfused pancreas, which maintains the polarity during every step of stimulus¡ªsecretion coupling. The steps that can be minitored by optical and NMR spectroscopy are shown schematically in Fig. 1.