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activation (30 min, 3.798 J/cm
2
), 16.8 % of the 1 mM ALA-treated Meth-A cells
were lysed (
P
0.05). When ALA and Oph were used jointly, specific cell lysis
increased over seven fold (P
<
0.05) compared to the ALA-treated cells.
<
19.5.3 Proto Accumulation in ALA and Oph Treated
Meth-A Solid Tumors In Vivo
Preliminary experiments on Proto accumulation in Meth-A tumors in vivo were
conducted using a range of ALA (1-10 mM) and Oph (0.75-7.5 mM) doses. In
general, the highest concentration yielded Proto accumulation levels
30 nmol/
100 mg protein whereas 1 mM ALA and 0.75 mM Oph yielded Proto levels of
1.1 nmol/100 mg. Therefore, for the next series of experiments, doses ranging from
2.5 to 10 mM ALA were used at different time points (Rebeiz et al.
1996b
).
Untreated tumors did not accumulate Proto, whereas significant amounts of
Proto accumulated after 3 and 6 h (31 and 17 nmol/100 mg protein, respectively)
were observed at the highest dosage of ALA and Oph tested. Twelve hour or more
after injection, the levels of accumulated Proto were lower, probably due to
degradation by intracellular enzymes (Mattheis and Rebeiz
1977
).
A similar pattern of decline in Proto accumulation in single-cell suspensions of a
T-cell lymphoma (MLA 144) incubated with 0.5 mM ALA and 0.38 mM Oph for
18 h was also observed. The amount of accumulated Proto fell over tenfold at
18
versus
3 h (1.7
>
2).
Because substantial Proto had accumulated 3 h after injection with ALA and
Oph, this time point was used in subsequent experiments. The next series of
experiments focused on the enhancement of ALA-induced Proto accumulation by
Oph in Meth-A solid tumors (Rebeiz et al.
1996a
) Previous studies with Oph had
shown that the optimal Oph concentration to use was about 75 % of the used ALA
concentration (Rebeiz et al.
1990
). As before, medium-treated tumors or tumors
treated with Oph alone at 1.8, 3.75, or 7.5 mM did not accumulate any Proto. Oph at
two concentrations, 7.50 and 3.75 mM, enhanced Proto accumulation in the pres-
ence of 10 (2.7-fold) and 5 (4.7-fold) mM ALA, respectively (
P
0.16
versus
19.6
9.90 nmol/100 mg protein;
n
ΒΌ
0.05). However,
at 1.8 mM, Oph did not enhance Proto accumulation when used in conjunction
with 1 mM ALA.
<
19.5.4 Effect of ALA and Oph Treatment on the Size
and Histopathology of Meth-A Solid Tumors
Having established that Meth-A tumors accumulate Proto after in vivo injection
with ALA and Oph the effects of ALA and Oph phototreatment of the tumors
were next investigated by histopathological examination of the tumor and the
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