L. Rosenberg et al., PARACRINE AUTOCRINE REGULATION OF PANCREATIC LET CELL-PROLIFERATION AND DIFFERENTIATION IN THE HAMSTER - STUDIES USING PARABIOSIS/, Clinical and investigative medicine, 19(1), 1996, pp. 3-12
Partial obstruction of the pancreatic duct in hamsters leads to new is
let formation and reversal of streptozotocin diabetes. The purpose of
this study was to delineate the mechanism by which endocrine cell prol
iferation and differentiation is mediated in this model. Six pairs of
parabiotic hamsters were established and partial duct obstruction was
inducted in 1 parabiont from each pair. At 6 weeks, the pancreatic wei
ght (mg/100g bw); DNA (mu g/100g bw) and protein content (mg/100g bw)
showed 28% (167 +/- 21 vs. 130 +/- 17), 32% (1,052 +/- 206 vs. 795 +/-
159), and 20% (25.4 +/- 6.6 vs. 21.2 +/- 1.9) increases (p < 0.05), r
espectively, over the non-wrapped parabionts. Morphometric analysis de
monstrated the presence of new islets in the wrapped pancreata with a
100% increase in the number of islets/mm(2) compared with non-wrapped
controls (0.90 +/- 0.5 vs. 1.8 +/- 0.7, p < 0.01). A cytosol extract w
as prepared from duct-obstructed pancreases, and 4 mu l/g bw injected
i.p. twice daily for 2 d produced significant increases in pancreatic
weight and DNA content of 12% and 40%, respectively. Cytosol extract f
rom non-wrapped pancreata had no effects compared with saline. When wr
apped cytosol extract was injected for 21 d, the labeling index of duc
tular and islet cells (% cell nuclei labeled with H-3-TdR) was increas
ed 10- and 6-fold respectively over controls (2.42 +/- 0.28 vs. 0.23 /- 0.01 and 1.17 +/- 0.01 vs. 0.25 +/- 0.04, respectively, p < 0.01).
The trophic effects observed in this model of islet cell proliferation
and differentiation did not appear to be mediated by a humoral mechan
ism because the changes induced by partial obstruction were not observ
ed in the non-operated parabiont. Control of pancreatic endocrine cell
growth in this model appears to involve paracrine and/or autocrine re
gulatory mechanisms.