H. Mineo et al., EFFECTS OF C-TERMINAL FRAGMENTS OF CHOLECYSTOKININ ON PLASMA-INSULIN AND GLUCAGON CONCENTRATIONS IN SHEEP, Research in Veterinary Science, 62(2), 1997, pp. 171-174
The effects of three C-terminal fragments of cholecystokinin (CCK) (CC
K-8-sulphated form [SF], CCK-8-non-sulphated form [NSF] and CCK-4) on
insulin and glucagon secretion were examined in sheep in vivo. Each CC
K fragment was injected intravenously at a wide range of doses (1 pmol
to 3 x 10(5) pmol kg(-1)). CCK-8(SF) had the lowest threshold dose (1
0 pmol kg(-1)) and a maximal response dose of 10(3) pmol kg(-1) for in
creasing plasma insulin concentration; the respective threshold doses
of CCK-8(NSF) and CCK-4 for increasing plasma insulin were 30 and 100
times greater than that of CCK-8(SF). A maximal insulin response was n
ot obtained at the highest doses of CCK-8(NSF) or CCK-4 tested (3 x 10
(3) and 3 x 10(5) pmol kg(-1), respectively). These results indicate t
hat CCK-A type receptors rather than CCK-B receptors may be involved i
n CCK-induced insulin secretion in sheep. None of the CCK fragments af
fected plasma glucagon concentration. The lack of a glucagon response
to exogenous CCK fragments may be one of the characteristics of the en
docrine pancreatic responses of ruminant species.