Objective: Octreotide, a somatostatin analogue, has
been shown to prevent angiogenesis in diverse in
vitro models. We evaluated its effect on retinal neovascularization
in vivo, using a neonatal rat retinopathy
model.Methods: We used, on alternating days, hypoxia
(10% O2) and hyperoxia (50% O2) during the first 14
days of neonatal rats, to induce retinal neovascularization.
Half of the rats were injected subcutaneously
with octreotide 0.7 μg/g BW twice daily. At
day 18 the eyes were evaluated for the presence of
epiretinal and vitreal hemorrhage, neovascularization
and epiretinal proliferation. Octreotide pharmacokinetics
and its effect on serum growth hormone
(GH) and insulin-like growth factor I (IGF-I) were
examined in 28 rats.Results: Serum octreotide levels were 667 μg/1 two
hours after injection, 26.4 μg/1 after nine hours and
3.2 μg/1 after 14 hours. GH levels were decreased
by 40% (p = 0.002) two hours after injection but
thereafter returned to baseline. IGF-I levels were unchanged
two hours after injection and were elevated
by 26% 14 hours after injection (p = 0.02). Epiretinal
membranes were highly associated with epiretinal
hemorrhages (p < 0.001), while retinal neovascularization
was notably associated with vitreal hemorrhages (p < 0.001).Conclusions: Twice-daily injections of octreotide
failed to produce sustained decrease in serum GH,
but produced rebound elevation of serum IGF-I.
Accordingly, no statistically significant effect of injections
on retinal pathology was noted. This finding,
however, does not contradict our assumption
that GH suppression may decrease the severity of
retinopathy.
