Summary
In ducks, the infusion of somatostatin (at a rate of 800 or 200 ng/kg/min for 30 min)
elicited a prompt (within 5 min) fall in the plasma free fatty acids (FFA) levels.
This effect is not mediated via modifications of pancreatic functions or growth hormone
secretion as it occurs in pancreatectomized and hypophysectomized ducks infused with
somatostatin, suggesting that it has a direct antilipolytic effect on adipose tissue.
In intact ducks the infusion of somatostatin increased the level of plasma glucagon-like-immunoreactivity
(GLI). As this effect was not observed in pancreatectomized birds glucagon solely
of pancreatic origin is involved in the response to somatostatin.
To determine if somatostatin affected pancreatic A cells via lipid metabolism, ducks
were infused with a mixture of somatostatin and oleic acid (in order to avoid the
drop in plasma FFA levels induced by somatostatin). In controls, infused with oleic
acid alone (at a rate of 12 mg/kg/min) plasma FFA levels rose and plateaued at the
end of the infusion period. The levels of plasma immunoreactive glucagon (IRG) were
reduced in control ducks during oleic acid infusion. When somatostatin (200 ng/kg/min)
and oleic acid (12 mg/kg/min) were infused together the rise in FFA was similar during
the first 20 min but by 30 min the levels had been reduced to the pretreatment concentration.
In those birds IRG secretion was not reduced as in the controls and following infusion
a rebound increase in IRG occurred. The infusions of oleic acid (6 mg/kg/min) with
somatostatin (200 ng/kg/min) induced no change in FFA levels but blunted the IRG stimulation
observed in birds infused with somatostatin alone.
These findings suggest that somatostatin is a potent antilipolytic hormone in ducks
and that the stimulatory effect of somatostatin on glucagon secretion may be secondary
to the inhibition of FFA release.
Key-Words:
Ducks
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Glucagon Like Immunoreactivity
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Immunoreactive Glucagon
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Somatostatin
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Free Fatty Acids
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Hypophysectomy
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Pancreatectomy
