Effect of pre-treatment of alpha-ketoglutarate on cyanide-induced toxicity and alterations in various physiological variables in rodents.
OBJECTIVE
To investigate the effects of pre-treatment of alpha-ketoglutarate (alpha-KG) on cyanide-induced lethality and changes in various physiological parameters in rodents.


METHODS
The LD50 of potassium cyanide (KCN) given orally (po), intraperitoneally (ip), subcutaneously (sc) or intravenously (iv) was determined in male mice, in the presence or absence alpha-KG given po, ip or iv. alpha-KG was administered 10, 20 or 40 min prior to KCN at 0.50, 1.0 or 2.0 g/kg by po or ip route, and at 0.10, 0.20 or 0.40 g/kg by iv route. Protection index (PI) was calculated as the ratio of LD50 of KCN in the presence of alpha-KG (protected animals) and LD50 of KCN in the absence of alpha-KG (unprotected animals). In a separate experiment, several physiological variables viz. mean arterial pressure (MAP), heart rate (HR), respiratory rate (RR), neuromuscular transmission (NMT) and rectal temperature (RT) were measured in anesthetized female rats pre-treated (-10 min) with po (2.0 g/kg) or iv (0.125 g/kg) alpha-KG and then administered sub-lethal (0.75 LD50) or lethal (2.0, 4.0 or 8.0 LD50) doses of KCN (po).


RESULTS
PI of 4.52, 6.40 and 7.60 at -10 min, 3.20, 5.40 and 6.40 at -20 min, and 1.40, 3.20 and 5.40 at -40 min of po administration with a-KG was observed for 0.50, 1.0 and 2.0 g/kg doses, respectively, against KCN given by po route. When KCN was given ip, a PI of 3.38, 4.79 and 5.70 was observed for 0.50, 1.0 and 2.0 g/kg alpha-KG given ip (-10 min), respectively. A lower PI of 3.37, 2.83 and 2.38 was observed when KCN given sc was challenged by 2.0 g/kg alpha-KG given ip at -10, -20 or -40 min, respectively. Similarly, a PI of 3.37, 2.83 and 2.0 was noted when KCN given sc was antagonized by 2.0 g/kg alpha-KG given po at -10, -20 or -40 min, respectively. No appreciable protection was observed when lower doses of alpha-KG (ip or po) challenged KCN given by sc route. Pre-treatment of iv or po administration of alpha-KG did not afford any protection against KCN given po or iv route. Oral treatment of 0.75 LD50 KCN caused significant decrease in MAP and HR after 15 min, RR after 30 min and NMT after 60 min. There was no effect on RT. No reduction in MAP, HR, RR and RT was observed when rats received 2.0 or 4.0 LD50 KCN after pre-treatment of alpha-KG (po; 2.0 g/kg). However, no protection was observed on NMT. Protective efficacy of alpha-KG was not observed on MAP, HR, RR, and NMT decreased by 8.0 LD50 KCN. Decrease in MAP and NMT caused by 2.0 LD50 KCN (po) was resolved by iv administration of alpha-KG.


CONCLUSIONS
Cyanide antagonism by alpha-KG is best exhibited when both alpha-KG and KCN are given by po route. The protective effect of a-KG on cyanide-induced changes in several physiological parameters also indicates a promising role of alpha-KG as an alternative cyanide antidote.
Tulsawani
Rajkumar
R
Division of Pharmacology and Toxicology, Defence Research and Development Establishment Jhansi Road, Gwalior, M. P., India.
Kumar
Deo
D
Bhattacharya
R
R
D000284:Administration, Oral; D000818:Animals; D000931:Antidotes / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D005260:Female; D007274:Injections, Intraperitoneal; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D007656:Ketoglutaric Acids / Q000008:administration & dosage*; D007928:Lethal Dose 50; D008297:Male; D051379:Mice; D011190:Potassium Cyanide / Q000506:poisoning*; D051381:Rats; D017208:Rats, Wistar
D000931:Antidotes; D007656:Ketoglutaric Acids; D011190:Potassium Cyanide