Alteration of glucose metabolism in liver by acute administration of cannabis
Author: P. SANZ, C. RODR?GUEZ-VICENTE, M. REPETTO
Pages: 31 to 35
Creation Date: 1985/01/01
Instituto Nacional de Toxicolog?a, Seville, Spain
In previous research on the effects of cannabis on cellular functions the authors observed an increase in glucose metabolism in the postmitochondrial fraction of the liver of rats submitted to chronic administration of cannabis extracts. Continuing this research on rats submitted to acute cannabis intoxication a single dose of cannabis extract (600 mg/kg) in olive oil is administered to male adult rats and the animals are killed within a 36-hour period. The analyses show that energetic and detoxifying metabolism of glucose is increased, as indicated by the increase of F-1, 6-di P-aldolase and uridin-diphosphoglucose-dehydrogenase activities, which parallels the observed decrease of glycogen levels. Maximum effect appears between 8 and 16 hours after administration.
In previous research on the effects of cannabis on the cell the authors observed that the administration of the active resin to rats produced a strong impairment of hepatic glycogen, which was not related to any modification of intracellular or extra-cellular glucose  .
In recent studies designed to elucidate the possible alteration of glucose metabolism the authors have shown  that both acute and chronic administration of cannabis mobilizes the intracellular stores of glycogen in liver, thus agreeing with the results of other authors   . The maintenance of normal levels of serum and liver glucose was explained by a strong increase in both energetic and detoxicating glucose metabolism. The results of the authors' research on the evolution of these biochemical parameters in rats submitted to acute cannabis intoxication are summarized in this article. The authors have also attempted to clarify the contradictory results, such as hypoglycaemia   , hyperglycaemia  and diabetic coma  , reported by different investigations in relation to serum glucose levels in both animals and humans.
Having extracted cannabis plant material with petroleum ether (boiling point 40° - 60°C), cannabinoid content was estimated and the residue was dissolved in olive oil for administration to animals. One hundred adult male Wistar rats, weighing 150 - 200 grams, were caged in groups of three. Food and water were available ad libitum.
A single 600 mg/kg dose was injected into 58 rats subcutaneously and the animals were killed by decapitation 4, 8, 12, 16, 20, 24 and 36 hours after the administration of the drug, and blood and liver samples were taken for analysis. Samples from control groups of untreated animals (26 rats) and animals (16 rats) treated with olive oil were also analysed.
Liver samples were homogenized in 5 volumes of 0.25 sucrose-10mM hepes and post-mitochondrial fraction (pmf) was obtained after 30 minutes centrifugation at 18,000 rev/min  . Glucose was determined in serum and pmf of the liver by the glucose-oxidase method  . Glycogen was determined after alkaline digestion of liver by the anthrone reaction according to Seifter  . Fructose-l, 6-di P-aldolase was determined in liver pmf by a coupled enzymatic assay  . Uridin-diphosphoglucose-dehydrogenase (UDPG-DH) was determined in liver pmf in accordance with Gayney and Phelps  . Protein concentration was estimated by the Lowry method  .
There was no significant modification of glucose levels in either serum or liver at almost any time of the acute intoxication (see table 1), but serum glucose decreased by 40 per cent; eight hours after the administration of cannabis, from the mean value found in control animals, while liver glucose increased by 27.2 per cent four hours after the administration of cannabis and then returned to a normal level. Liver glycogen considerably decreased 4 hours after the administration of cannabis and after 20 hours it showed a slight restoration.
Table 2 shows that the enzymatic activities of F-1, 6-di P-aldolase and UDPG-DH increased. F-1, 6-di P-aldolase showed a maximum induction 12 hours after the administration of cannabis. UDPG-DH increased strongly, but the increase oscillated considerably.
The study of the evolution of different parameters and enzymatic activities related to glucose metabolism in liver after the administration of a single dose of cannabis to rats confirmed the results that the authors had previously found in chronically intoxicated rats. The first action of cannabis on the hepatic cell seemed to be the mobilization of glycogen stores. The released glucose was quickly metabolized as shown by the increase in both the energetic metabolism (F-1, 6-di P-aldolase) and the detoxicating metabolism (UDPG-DH). Thus the glucose was consumed at the same rate as it was released from glycogen, which explained why no major oscillation could be observed in serum or liver glucose levels. The alteration of those levels was only observed early in the acute intoxication; 4 hours after the administration of cannabis, glucose increased in liver, probably due to a delay in the induction process of the enzymatic systems.
Serum and liver glucose and glycogen levels in rats submitted to acute cannabis intoxication
|Group||Time a hours||mg/ml||Percentage||mg/ml||Percentage||mcg/ml||Percentage|
group of animals
aTime between cannabis administration and death of animals; mean values for six animals.
bMean values for 22 animals.
cMean values for 26 untreated animals.
dMean values for 16 animals treated with olive oil and killed 24 hours after the administration of olive oil.
F-1, 6-di P-aldolase and UDPG-DH activities in livers of rats submitted to the acute cannabis intoxication
|Group||Time a(hours)||F-1, 6-di, P-aldolase b||Percentage||UDPG-DH b||Percentage|
of animals that
aTime between cannabis administration and death of animals; mean values for six animals.
bActivities expressed as nmol. NAD/mg protein/min.
cMean values for 22 animals.
dMean values for 26 untreated animals.
eMean values for 16 animals treated with olive oil and killed 24 hours after the administration of olive oil.
Nearly eight hours after the administration of cannabis, the strong increment of glucose metabolism produced a transient hypoglycaemia, which was then quickly restored, because 12 hours after the administration of cannabis blood sugar values were normalized. This fluctuation explains the contradiction in the reported results of other authors, because the blood sugar level changes according to the intoxication time at which the experiment has been carried out. These findings are in agreement with the observation by Pasquale and others  concerning dogs subjected to a single dose of tetrahydrocannabinol.
According to F-1, 6-di P-aldolase values, the maximum effect upon the energetic metabolism of glucose took place 12 hours after the administration of cannabis and was re-established after 20 hours, whereas the detoxicating mechanism (UDPG-DH) remained higher after 24 hours, coinciding with low glycogen levels.
The foregoing findings indicate that cannabis increases the energetic requirements of the cell. It also mobilizes the enzymatic system which are necessary for its own metabolism; these actions occur at the expense of intracellular stores of glycogen. It is also recognized that an important effect of cannabis is the inhibition of the synthesis of nucleic acids and proteins  . Consequently, the enzymatic systems must be inhibited as well. The fact that with glucose metabolism just the opposite is observed suggests that this must be a specific effect. It would also confirm the opinion of Luthra and Rosenkrantz  concerning the observed decrease in macromolecules as a result of other biomolecules, besides sugars and polysaccharides, functioning as energetic substrates.
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