Comprehensive formal models for pancreatic calcium secretion. With reference to "exchange-diffusion," "two-component," and "unicellular" models of electrolyte secretion.

This is a theoretical paper in which comprehensive formal models are developed for all possible modes of entry of calcium into pancreatic juice. The 15 models include entry via: (1) the chloride-rich secretion, (2) the bicarbonate-rich secretion, (3) protein-bound calcium, and (4) interstitial fluid (ISF), plus the various possible combinations of these. Equations are presented for both calcium-volume and calcium-bicarbonate relationships. Each equation is modified as necessary to conform to the three current models for sodium, chloride, and bicarbonate secretion: (1) "exchange-diffusion," (2) "two-component," and (3) "unicellular" models. We believe the models provide a sound theoretical framework on which to build an understanding of pancreatic calcium secretion. Subsequent papers will be concerned with the physicochemical state of calcium in the juice, the relative contribution of ISF, and the development of an overall model for pancreatic calcium secretion. The long-term objective is to provide a rational approach for the understanding of pancreatic calcification and stone formation.