EXOCRINE INTERSTITIAL INSULIN AND SOMATOSTATIN IN THE PERFUSED DOG PANCREAS

To determine whether the islet-acinar relationship is mediated microva scularly or by diffusion from islets, isolated dog pancreata were perf used anterogradely (n = 4) or retrogradely (n = 5). Interstitial fluid (ISF) was sampled utilizing a microdialysis technique. Three to five microdialysis probes were placed in the dorsal lobe of each pancreas. Insulin and somatostatin were measured in dialysate, as well as in per fusate, under both resting (5.6 mM glucose) and stimulated (12.2 mM gl ucose plus 20 mM arginine) conditions. During the stimulative period, retrograde ISF responses were markedly less than anterograde responses , whereas perfusate (intravascular) anterograde and retrograde respons es were not different; ratios of the sum of increments above basal lev els of ISF concentrations to the sum of increments of perfusate concen trations (SIGMADELTAISF/SIGMADELTAperfusate) of insulin and somatostat in during anterograde vs. retrograde perfusion were 35.1 +/- 8.8 (SE; n = 9) vs. 13.8 +/- 2.8% (n = 10) and 37.1 +/- 14.2 (n = 7) vs. 8.5 +/ - 4.2% (n = 9), respectively (both, P < 0.05). These data strongly sug gest that these islet hormones may be delivered to the exocrine inters titial space via a directed microcirculation from the islet to the aci nar tissue.