Toxicity, biodistribution and radioprotective capacity of L-homocysteine thiolactone in CNS tissues and tumors in rodents: Comparison with prior results with phosphorothioates
ORCiD
0000-0001-9010-5970
Document Type
Article
Publication Title
Radiotherapy and Oncology
ISSN
0167-8140
Volume
35
Issue
3
DOI
10.1016/0167-8140(95)01543-P
First Page
216
Last Page
226
Publication Date
6-1-1995
Abstract
l-Homocysteine thiolactone (L-HCTL) was evaluated for its potential as an intravenously-administered central nervous system (CNS) radioprotector in C3H mice and F344 rats. Toxicity assessments in the mouse yielded a LD50 of 297 mg/kg and in the rat 389 mg/kg. Biodistribution studies in tumor-bearing mice showed that brain specimens contained more label at 10 min than the tumors but less at 30 or 60 min. Brain uptake relative to the tumors, the brain/tumor ratio, ranged between 0.5 and 3.3. The cervical spinal cord of non-tumor-bearing rats was irradiated with 32 Gy 137Cs with or without prior treatment with l-HCTL following which the time to forelimb or hindlimb paralysis was measured to determine the relative protective factors (RPFs) for this radiation dose. For forelimb paralysis the RPF was 1.9 (± 1.0, SD) and for hindlimb it was 2.0 (± 1.1, SD). 36B-10 glioma cells irradiated in vitro with or without l-HCTL and assayed for colony forming capacity demonstrated a dose modifying factor (DMF) of only 1.15 (±0.16, SE). Rats bearing intracerebral 36B-10 glioma received 137Cs irradiation with or without l-HCTL after which the tumors were similarly assayed in vitro. From this the glioma DMF was 1.2 (±0.30, SE). Compared to prior results with phosphorothioates our data show that the toxicity of l-HCTL is roughly the same as WR2721, WR77913 and WR3689 and that it distributes at higher levels in the CNS after systemic administration. l-HCTL may well equal these phosphorothioates at protecting normal CNS tissue without requiring administration directly into the cerebrospinal fluid-containing spaces and it does not protect the 36B-10 glioma.
Recommended Citation
Spence, A. M.,
Rasey, J. S.,
Dwyer-Hansen, L.,
Grunbaum, Z.,
Livesey, J. C.,
Chin, L. K.,
Nelson, N. J.,
Stien, D.,
Krohn, K. A.,
&
Ali-Osman, F.
(1995).
Toxicity, biodistribution and radioprotective capacity of L-homocysteine thiolactone in CNS tissues and tumors in rodents: Comparison with prior results with phosphorothioates.
Radiotherapy and Oncology, 35(3), 216–226.
DOI: 10.1016/0167-8140(95)01543-P
https://scholarlycommons.pacific.edu/phs-facarticles/182
