Functional differences between rat islets of ventral and dorsal pancreatic origin.

Abstract

A B S T R A C T Do functional linkages between islet endocrine cells exist? The effect of differences in frequency and distribution of islet endocrine cells on B cell function was examined in islets from the ventral (ventral islets) and dorsal (dorsal islets) areas of the rat pancreas.Dorsal islets contained 10 times as much glucagon as ventral islets, whereas insulin and total protein contents were similar. Basal rates of insulin secretion and proinsulin biosynthesis were similar in the two types of islet, but, under conditions of glucose stimulation, both insulin secretion and proinsulin biosynthesis were significantly greater in the glucagon-rich dorsal islets. Similarly, glucose utilization rates and ATP levels were greater in dorsal islets. In contrast, the rates of processing of newly synthesized proinsulin were similar in ventral and dorsal islets. That the islet glucagon content may have affected B cell function is inferred from two independent findings. Firstly, basal and glucose-stimulated cyclic AMP contents of glucagon-rich dorsal islets were greater than those of ventral islets. Secondly, in the presence of excess exogenous glucagon (1 ug/ml), the differences in glucose-induced insulin secretion and proinsulin biosynthesis rates between the two types of islets were eliminated.These results strongly suggest that changes in the relative proportions of the different islet endocrine cells exert marked effects on islet function. In particular, a greater A cell and glucagon content is associated with higher rates of glucose-induced insulin secretion and biosynthesis.

Role of islet structure and cellular interactions in the control of insulin secretion

“…1 These findings illustrate that interactions of islet cells and changes in their relative proportions have marked effects on insulin release.…”

An Investigation of the Relationship between Duct System and A Cell-Rich and PP Cell-Rich Pancreatic Islets in the Canine Pancreas.

“…These two types of pancreatic islets do not, however, exist randomly but are separate and exist in small areas. At present, the established theory is that the A cell-rich area derives from the dorsal pancreas and the PP cell-rich area derives from the ventral pancreas, since these is a embryological correspondence between each area and the region of the pancreas from which it is derived [1,17,18].…”

Contents and secretion of glucagon and insulin in rat pancreatic islets from the viewpoint of their localization in pancreas.

“…In the present experiment the size of pancreatic islets did not differ between the dorsal lobe and the ventral lobe, and the IRG content in the islets was significantly high in the former. Trimble et al (1982) mentioned that dorsal lobe islets contain more IRG than do ventral lobe islets, and IRI secretion and proinsulin biosynthesis were greater in the dorsal lobe islets under the condition of glucose stimulation.…”

“…The contents of insulin and glucagon in the pancreas have been reported to be rich in the dorsal lobe compared with those in the ventral lobe (Wrenshall et al 1952: Orci andPerrelet 1981;Trimble et al 1982;Tasaka et al 1984). On the contrary, pancreatic polypeptide is abundant in the ventral lobe of the pancreas (Gingerich et al 1978;Gersell et al 1979;Orci and Perrelet 1981;Tasaka et al 1984).…”