Material and methods
Results
Conclusions
Summary
Author: A. DE PASQUALE, G. COSTA, A. TROVATO
Pages: 33 to 41
Creation Date: 1978/01/01
Cannabis resin, the effects of which on the activity of the central nervous system are well known, also influences the metabolism of glucides.
Carbonaro and Imbesi (1) report that liquid cannabis extract, administered intravenously to rabbits in doses of between 0.1 and 0.6 g/kg leads to an increase in the degree of glycaemia. El-Sourogy et al. (2) have observed a decrease in hepatic glycogen and an increase in haematic glucose after intramuscular administration of cannabinol in rabbits. Sprague et al. (3) also noted a decrease in hepatic glycogen after the administration, continued for 28 consecutive days, of r 9-THC, in different doses and by different means in the case of monkeys, rabbits and rats. Hughes et al. (4) further report that, in man, cannabis taken orally caused an increase in haematic glucose. Hollister and Reaven (5) observed a decrease in glucose tolerance after the intravenous administration of 6 mg of r 9-THC in man. Mahfouz et al. (6) report that in rats exposed to hashish smoke, the haematic glucose level rose by 24 per cent and the lactic-acid dehydrogenase and glutamic-oxalacetic-transaminasic activities increased significantly. Finally, Papadakis et al. (7) noticed a significant reduction in haematic lactic acid in hashish smokers.
In the research reported upon here, in addition to the effects of cannabis resin administered in different doses, on haematic glucide levels, studies have also been made of the plasmic immunoreactive insulin (IRI) levels and variations in the plasmic ammonia concentration. Experiments were performed on dogs either having had no food or having been fed glucose intravenously.
The cannabis resin used and analysed by gas chromatography (Lerner (8); Fetterman et al. (9)) contained 6.3 per cent of r 9-tetrahydrocannabinol (r 9-THC), 3.2 per cent of cannabidiol and 1.9 per cent of cannabinol. It was given to animals by intramuscular injections after having been dissolved in propylenic glycol, in doses corresponding to a content of r9-THC of 2.5,5 and 10 mg/kg of body weight respectively.
* Some of the research results given here were the subject of communications to the Joint Meeting of German and Italian Pharmacologists, Venice, 4-6 October 1977.
The resin was administered in the morning to animals which had been given no food since the previous day, but had been able to absorb some water. Blood samples were taken to supply the required information immediately before the resin was administered and successively after 30, 60, 90, 120, 180 and 240 minutes.
In the case of animals given a glucose feed, this was administered intravenously in a 33 per cent solution in doses of 0.33 g/kg, 90 minutes after the administration of the above-mentioned doses of resin and blood was taken for the doses 95, 105, 120, 150, 180 and 240 minutes after the administration of the resin.
The amount of haematic glucose was determined by the glucose-oxidase micromethod (Trinder (10)). Determination of immunoreactive insulin (IRI) was carried out by the radioimmunological method of Keane et al. (11), while the plasmic ammonia was ascertained by the enzyme method of Da Fonseca-Woll-heim (12).
In compiling statistics from the data, the arithmetic mean and the relative standard error were calculated for each time of observation. The significance of the difference in relation to the base values was estimated on the basis of "t" (or Student) distribution for associated data. In the experiments in which animals were given intravenous feeds of glucose, the results were related to control animals, which had been given only a glucose feed and, consequently, the significance was estimated by means of the "t" (or Student) distribution for unconnected data.
With the doses used, cannabis resin led to a progressive increase in haematic glucose (fig. I), which reached maximum values 90 minutes after administration; after 180 minutes the levels returned to normal, except in cases where very large doses of the medicament had been administered, i.e. 10 mg/kg of r 9-THC, when the values remained at a level well above the normal 240 minutes after administration.
With the increase in haematic glucose there was a corresponding reduction in plasmic IRI (fig. II). For the two strongest doses the decrease was significant already within 30 minutes of the administration. After 90 minutes the lowest levels of plasmic IRI concentration were reached; subsequently these values showed a more or less rapid recovery towards normal levels.
After the administration of the resin, the plasmic ammonia levels also showed progressive increases reaching the highest values after 90 minutes and then decreasing gradually down to the normal value.
In the experiments in which animals were first given an intravenous feed of glucose (fig. IV), it was found that, after the administration of cannabis, the glycaemia values remained at the highest levels for a longer period than in the control animals. It was for that reason that the return to normal took place more slowly and no change was detectable after 240 minutes even with the heaviest dose.
In these animals the insulin response was the same: plasma IRI levels, after the administration of resin, remained consistently lower than those of animals which had only been given a glucose feed (fig. V) and the fall in values was much greater with the highest resin doses.
Even the plasmic ammonia levels gave higher values than those in animals which had received only a glucose feed, and already returned to normal 180 minutes after the administration of resin, except in the case of the highest dose (fig. VI).
Dose A = dose corresponding to 2.5 mg/kg of r 9-THC.
Dose B = dose corresponding to 5.0 mg/kg of r 9-THC.
Dose C = dose corresponding to 10.0 mg/kg of r 9 9-THC.
Each point represents the Mean ± Standard Error of 6 experiments.
* P 0.05 in relation to the base value.
Dose A = dose corresponding to 2.5 mg/kg of r 9-THC.
Dose B = dose corresponding to 5.0 mg/kg of r 9-THC.
Dose C = dose corresponding to 10.0 mg/kg of r9-THC.
Each point represents the Mean ± Standard Error of 6 experiments.
*P 0.05 in relation to the base value.
Dose A = dose corresponding to 2.5 mg/kg of r 9-THC.
Dose B = dose corresponding to 5.0 mg/kg of r 9-THC.
Dose C = dose corresponding to 10.0 mg/kg of r 9-THC.
Each point represents the Mean ± Standard Error of 6 experiments.
*P 0.05 in relation to the base value.
Dose A = dose corresponding to 2.5 mg/kg of r 9-THC.
Dose B = dose corresponding to 5.0 mg/kg of r 9-THC.
Dose C = dose corresponding to 10.0 mg/kg of r 9-THC.
Each point represents the Mean ± Standard Error of 6 experiments.
* P 0.05 in relation to the base value.
Dose A = dose corresponding to 2.5 mg/kg of r 9-THC.
Dose B = dose corresponding to 5.0 mg/kg of r 9-THC.
Dose C = dose corresponding to 10.0 mg/kg of r 9-THC.
Each point represents the Mean ± Standard Error of 6 experiments.
* P 0.05 in relation to the base value.
Dose A = dose corresponding to 2.5 mg/kg of r 9-THC.
Dose B = dose corresponding to 5.0 mg/kg of r 9-THC.
Dose C = dose corresponding to 10.0 mg/kg of r 9-THC.
Each point represents the Mean ± Standard Error of 6 experiments.
* P 0.05 in relation to the base value.
The results obtained show that cannabis resin leads in dogs to a significant increase in haematic glucose, accompanied by a reduction in plasmic IRI and an increase in the amount of ammonia in the blood. Cannabis also leads to a fall in the tolerance of glucose administered intravenously: Hollister et al. (5) have observed similar phenomena in man after the administration of r 9-THC.
Prior and Visek (13) report that the increase in haematic ammonia levels was accompanied by an increase in glycaemia. Feldman and Lebovitz (14) have, on the other hand, observed that in the isolated and perfused pancreas of a hamster, ammonia leads to an inhibition of the secretion of insulin produced by glucose. Hales et al. (15) note that the increase in ammonia levels corresponded to an inhibition in the release of insulin by the pancreatic beta-cell because ammonia obstructed the entry of Ca+ + to its interior, thus preventing the activation of the retractile system of the micro-tubes and micro-filaments, and consequently the release of hormone.
It therefore appears possible that the variations in the haematic glucose and IRI levels observed after the administration of cannabis resin may be correlated with variations in ammonia which were verified in the same manner.
Lastly, as was observed in the case of experimental intoxication with ammonia in rats, there was an increase in glutamine in the brain and in fluids (16), an increase in the cerebral levels of gamma-amino-butylic acid (GABA) (17) and an inhibition of acetylcholine synthesis (18); it cannot therefore be excluded that the increase in the ammonia level may in part be correlated with some of the effects of cannabis on the central nervous system.
The effects of the administration of cannabis resin in different doses on haematic glucose levels, on plasmic IRI and on the amount of ammonia in the blood have been studied in dogs which had not been fed or had been fed intravenously with glucose.
The results show that such resin leads to an increase in haematic glucose, accompanied by a reduction in plasmic IRI and an increase in ammonia levels. In addition, a decrease is observed in the tolerance of glucose administered intravenously.
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