Le. Flores et al., MODULATORY EFFECT OF HORMONES ON INSULIN-SECRETION IN-VITRO IN THE TOAD, Comparative biochemistry and physiology. C. Comparative pharmacologyand toxicology, 120(1), 1998, pp. 77-81
The aim of this work was to demonstrate the possible direct effect of
several hormones upon glucose-induced insulin secretion in amphibians.
Hence, pancreas pieces of Bufo arenarum were incubated for 60 min at
25 degrees with 2 and 8 mM glucose plus the addition of hormones known
to affect insulin secretion in mammals, measuring the release of insu
lin by radioimmunoassay. Glucagon (1 mu M), ACTH (2.5 mu M), human and
bovine growth hormone (4.6 and 2.1 mu M), prolactin (0.27 mu M), cort
icosterone (0.4 mu M), androstanolone (10(-2) mu M), estradiol and est
rone (10 mu M), triiodothyronine and thyroxine (1 mu M) enhanced signi
ficantly the glucose-induced insulin secretion. Androstanolone, human
and bovine growth hormone, triiodothyronine and thyroxine only exerted
such effect in the presence of 8 mM glucose. Conversely, somatostatin
(1 mu M), adrenalin (1 mu M), clonidine (2 mu M), dexamethasone (0.4
mu M), and 2-hydroxyestradiol (5 mu M) decreased significantly the glu
cose-induced insulin release. However, the effect of somatostatin was
only apparent in the presence of high glucose. The direct effect of al
l these hormones-tested for the first time in the amphibian pancreas-w
as similar to that described in the mammalian pancreas, thus suggestin
g that such hormones might participate, at least in vitro, in the fine
-tuning of insulin secretion in amphibians. (C) 1998 Elsevier Science
Inc. All rights reserved.