AKIRA MIZUNO†, TAKASHI MURAKAMI†, SHIZUKA OTANI,
MASAMICHI KUWAJIMA, AND KENJI SHIMA
Department of Laboratory Medicine, School of Medicine, the University of Tokushima, Tokushima
770-8503, Japan
ABSTRACT
The effects of leptin on the secretion of insulin and glucagon were
examined. In an experiment involving insulin response to an iv glu-
cose load in vagotomized rats, the plasma concentrations of insulin
were significantly lower in the leptin (20 nmol/kg BW)-treated group
than in a control group. However, in intact rats and rats that had
undergone both vagotomy and chemical sympathectomy, this sup-
pressive effect of leptin on insulin secretion was not detected. In an
experiment involving a hypoglycemia-induced glucagon secretion test
in intact rats, an iv injection of leptin (20 nmol/kg BW) augmented the
plasma glucagon response to hypoglycemia. In the case of sympa-
thectomized rats, however, this stimulative effect of leptin on gluca-
gon secretion was not detected. In an experiment with perfused rat
pancreas, the addition of leptin (20 nM) to the perfusate slightly
suppressed insulin secretion, but had no effect on basal or glucopenia-
induced glucagon secretion. In intact rats infused with leptin (0.31
