July 1963 Ind. Journal Med. Res. 51. 4, pp.716-724

by S. S Gupta
In previous communications, Gupta et al. (1962) reported on the inhibitory effect of daily administration of a few Ayurdevic anti-diabetic…

Effects of Indigenous Anti-Diabetic Drugs Against the Acute Hyperglycemic Response of Anterior Pituitary Extract in Glucose Fed Albino Rats

Author: S. S Gupta

Type of Publication: Pre-Clinical

Date of Publication: July 1963

Publication: Ind. Journal Med. Res. 51. 4, pp.716-724, July 1963

Organization: Department of Pharmacology, Gandhi Medical College, Bhopal

In previous communications, Gupta et al. (1962) reported on the inhibitory effect of daily administration of a few Ayurdevic anti-diabetic remedies- Gymnema sylvestre and Tribang shila against the hyperglycemic response of anterior pituitary extract, while Gupta and Seth (1962) demonstrate their ameliorating effect in idio-hypophyseal diabetic condition in rats. Since the diabetogenic effect of anterior pituitary extract is effected through inhibition of glucose utilization by the tissues (Young, 1951), it would be of interest to investigate the effect of some commonly used indigenous anti-diabetic drugs against the acute hyperglycemic response of the anterior pituitary extract in fasting animals fed with glucose through stomach tube.

MATERIALS AND METHODS

The present investigations were conducted on adult male albino rats of Nowegian strain weighing between 175 g. and 200 g. The animals were kept in separate cages and fed ad libidum on stock diet as reported previously (Gupta et al., loc. cit.). Their fasting blood sugar determined every 5^th day for a control period of 15 days, was found to vary within the fiducial limits of 4.43 mg. per cent only.

After collecting the fasting blood, all animals were injected subcutaneously 100 mg./kg. dose of the anterior pituitary extract. The animals were then divided into five groups of six rats each. One hur the injection, half the animals in each of the groups I to V-insulin, were given respectively, the alcoholic extract of Gymnema sylvestre and Coccinia indica 9100 mg./kg. each), aqueous infusion of Pterocarpus marsupium (20 ml./kg.), extract of Momordica charantia Linn. (5 ml./kg.) and tolbutamide (50 mg../kg.) orally through a stomach tube. The remaining half of the animals in each goup were administered equivalent amount of the solvent distilled water to serve as controls. All the animals, irrespective of the groups were fed 50 per cent glucose (2 ml./100 g.) through tube after half an hour of administering drugs. The administration of drugs and glucose was given repeated after collecting 6^th hour blood samples. The blood sugar was then determined in the individual rats at 3^rd, 6^th, 12^th, and 24^th hours of the anterior pituitary injections. Cross over test was performed after a week when the blood sugar had returned to normal. Blood sugar was estimated as per Folin’s modification of Hagedorn Jenson’s method.

Drugs used were as follows: Alcoholic extracts of Gymnema sylvestre and Coccinia indica were prepared by extracting the dried leaves and roots, respectively, in ethanol for 5 hours in a Soxhlet apparatus. The dried residue was then re-dissolved in 1 part of alcohol, 2 parts of Twen 80 and 2 parts of water to prepare 200 mg./kg. solutions for oral administration.

Aqueous infusion of Pterocarpus marsupium was prepared by soaking 100 g. saw dust of the wood of P. marsupium in 200 ml. of water for 18 hours. The supernatant fluid was decanted off and volume adjusted so that 2 ml. of infusion represented 1 g. of the crude wood.

Aqueous extract of Momordica charantia Linn, was prepared by expressing out the juice from 100 g. of fresh fruits in an extractor. The juice was then diluted with distilled water to make 100 ml. of the extract.

Tolbutamide was given after powdering the tablet and then suspending in gum acacia for oral administration. The drug preparations were stored in sealed containers in refrigerator at 4⁰ C. for a week for the cross over tests.

Anterior pituitary extract use in the present investigation was prepared by M/s Bengal Immunity Co., Calcutta, from 1 g. of fresh pituitary gland (ox) homogenized with glycerine 1 ml., parachlorometacresol 0.05 g. and distilled water sufficient quantity to make 10 mg./ml. extract for subcutaneous injections.

RESULTS

Effect of the indigenous anti-diabetic drugs- Gymnema sylvestre and Coccinia indica on the hyperglycaemic response of the anterior pituitary extract in glucose fed rats is summarized in Table I. Rise in blood sugar level at 3,6,12, and 24 hours after administering the anterior pituitary extracts in control and treated rats is compared in Graph 1.

In apreliminary experiment, in which only anterior pituitary extract was given to the fasting animals, the blood sugar level was found to be lowered (though not significanty P>0.05) in a few rats by 3^rd hour but it gradually increased by 6^th hour and remained appreciably high by 12^th hour. The increase in blood sugar was more marked in rats fed glucose solution twice during the day and the hyperglycaemic was observed to persist by 24 hours. The average percentage increase in blood sugar in the drug treated groups of rats was found to be lowe as compared to that controls as shown in Table II and Graph 2.

DISCUSSION

In the present investigations, inhibitory effect of the common indigenous oral anti-diabetic drugs-Gymnema sylvestre, Coccinia indica, Pterocarpus marsupium Momordica charantia Linn. have been observed against the acute hyperglycaemic response of anterior pituitary extract and compared with that of tolbutamide. The blood sugar level in each of the control sets, increased gradually after the 3^rd hour and reached maximum only after 12 hours of the administration of the anterior pituitary extract. The rise in blood sugar level during 3^rd hour of administation of anterior pituitary extract seems to be due to the direct effect of glucose absorbed from the gastro-intestinal tract, in view of the fact that within this period, anterior pituitary extract per se did not cause any significant change in the blood sugar level of fasting animals in our preliminary experiments. Therefore, the 3^rd hour blood sugar values (one and half hour after glucose administration) seem to be indicative of the glucose tolerance in the treated and untreated groups. Analysis of the data presented in the Table I would show that the indigenous anti-diabetic drugs, under study, have a favourable influence on glucose tolerance in view of the fact that the blood sugar level did not rise much in treated animals as compared to the controls (Graph I). This inhibitory effect was more marked in animals treated with the alcoholic extract of G. sylvestre, aqueous infusion of P. marsupium and M. cahrantia extract. This is in conformity with previous observations on the glucose tolerance after these drugs in normal fasting animals, as reported elsewhere (Gupta, 1963; Gupta and Seth, 1962a). On the other hand, insignificant or doubtful lowering of fasting blood sugar has been reported after some of these drugs (Chopra et al., 1928; Gupta and Seth, 1962). It is therefore, likely that the drugs might sentisize the pancreatic islets tissue for the secretion of insulin occurring in response to glucose hyperglyceamic (Best and taylor, 1955) or to the increased peripheral demand for insulin induced by the anterior pituitary hormones (Mirsky et al., 1959) which have been reported to cause initial hypoglycaemia in hypophy-sectomised rats (park et al., 1952). The inhibitory effect of Pterocarpus marsupium, however, amy also be related to the retardation of glucose absorption from the gastrointestinal tract by the drug as reported by Joglekar et al., (1959). The blood sugar level in tolbutamide –treated animals, on the other hand, was found to be higher than the controls. This decreased tolerance after the drugs seems to be in conformity with that reported by others (Holt and Holt, 1956; Leaderer and De Myer, 1957; Mohnike, 1957; Mukherjee et al., 1958).

The blood sugar level was observed to be significant (37.5 mg. per cent at P>0.05) raised in control animals by the sixth hour of the administration of the anterior pituitary extract. This hyperglycaemia seems to be related to the increased gluconeogenesis (Houssay, 1936; Long, 1973) as well as to the inhibition of the peripheral utilization of glucose effected by the anterior pituitary hormones (Young, lic. cit.) An appreciable inhibition of the hyperglycaemic response of the anterior pituitary extract was observed in animals treated with the oral anti-diabetic drugs under investigations, as would be apparent on comparing blood suagr levels of control and treated animals in Graphs 1 and 2. This inhibitory effect was most marked and significant (P<0.001) in animals of Group I, treated with the alcoholic extract of G. sylvestre which has also observed to inhibit epinephrine hyperglycaemia (Gupta, 1961) known to be mediated through gluconeogenesis (Vogt, 1944). Reduction in the blood sugar level in animals treated with the aqueous extract of M. charantia was also quite significant (P<0.05). The inhibition of the hyperglyceamic response was however, not found to be significant (P>0.05) after other drugs. The delayed reduction in the blood sugar of these anterior pituitary treated hyperglycaemic animals after tolbutamide was similar to that observed in diabetic patients (Krantz and Carr, 1961).

The hyperglycaemic effect of the anterior pituitary extract was well marked by the 12^th hour and seems to be related to the inhibition of the oxidation of the 2^nd dose of glucoseadministered after sixth hour. Increase in the blood sugar level was, however, less marked in drug treated animals as compared to their counterpart controls. Marked percentage inhibition of the hyperglyceamic response of the anterior pituitary extracts occurred after both tolbutamide and G. sylvestre (Table II), though the inhibitory effect of the latter only was found to be very highly significant (P=0.001). Reduction in blood sugar after other drugs under study, was also quite appreciable but their inhibitory effect was not found to be significant (P>0.05).

The blood sugar level was found to be elevated even after 24 hour, though appreciably levels were observed drug treated animals as compared to the controls. Inhibitory effect of tolbutamide and G. sylvestre was again found to be maximum and highly significant (P=0.01 and 0.001, respectively). Reduction in blood sugar level, next in order was found to be in the animals treated with M.charantia Linn (groupIV), P. marsupium (group III) and Coccinia indica (group II). The difference in the blood sugar of treated rats as compared to their counterpart controls in these groups was, however, significant (P<0.02) only in animals given the aqueous infusion of P. marsupium.

Thus, the marked and highly significant inhibitory effects of gymnema sylvestre and Tolbutamide against the hyperglycaemic response of the anterior pituitary extract observed after 24 hours, seem to substantiate the previous reports on these drugs (Gupta et al., loc. cit.; Mirsky et al., loc. cit.). Though this persistent hyperglycaemic response of the anterior pituitary has been demonstrated to be due to the inhibition of the glucose uptake by the tissues (park, 1952; Krahl, 1956(, but in absence of any positive evidence it would be difficult to postulate a direct influence of these drugs on glucose utilization in the hexokinase reaction, which is known to be inhibited by the anterior pituitary hormones (Price et al., 1946). An indirect effect of the drugs, through stimulation of the pancreatic insulin secretion, therefore, seems to be responsible for this inhibition, as has also been suggested by others (Mhaskar and Caius, 1930; Loubatieries, 1957). The persistent effect of G. sylvestre can, however, be related to the inhibition of the adrenocortico activity (Gupta and variyar, 1961) which is known to potentiate the inhibition of the hexokinase reaction caused by the anterior pituitary extract, while that of the tolbutamide to the inhibition of the insulinase activity as postulated by Mirsky et al.(1957).

The inhibitory effect of M. charantia though not found to be significant after 12 and 24 hours, in the present investigations has, however, been reported to potentiate and prolong the tolbutamide action on blood sugar in rabbits (kulkarni and gaitonde, 1962). This may be indicative of the potentiation of insulin secretion by the extract of M. charantia similar to that effected by tolbutamide. The anti-diabetic effect of P. marsupium and C. indica which also caused appreciable inhibition of the hyperglycaemic response of the anterior pituitary extract and have been reported to cause hypoglycaemia fasting animals (Ojha et al., 1949; De and Mukerjee, 1953) is also likely to be due to some indirect stimulation of pancreatic insulin secretion or to retardation of glucose absorption, in view of the fact that the hyperglycaemic effect of the anterior pituitary hormones is inhibited in fasted, insulin treated animals (Best et al., 1942; Luken et al., 1943).

The inhibition of the hyperglycaemic response of the anterior pituitary extract by some of these drugs, is likely to prevent the vicious cycle of hyperglycaemia responsible for the deterioration of the pancreatic lesion in diabetic (lukens, cited by Mukherjee et al., 1958). Thus, the beneficial effects of these indigenous drugs in some cases of milder diabetic states may be related to the inhibition of the noxicious influence of anterior pituitary hormones.

SUMMARY

1. Effect of oral administration of some of the indigenous oral anti-diabetic drugs- Gymnema sylvestre, Coccinia indica, Pterocarpus marsupium. Momordica charantia Linn. and tolbutamide has been investigated at 3,6,12 and 24 hours against the oral hyperglycaemic response of anterior pituitary extract injected subcutaneously in albino rats.

2. The alcoholic extract of G. sylvestre, aqueous infusion of P. marsupium and the aqueous extract of M. charantia Linn. inhibited the hyperglycaemia of the 3^rd hour (one and half hour after glucose administration) probably by influencing the glucose tolerance inthese animals.

3. Inhibition of the hyperglycaemic response of the anterior pituitary extract at 6,12 and 24 hours was most marked after both tolbutamide and G. sylvestre. Inhibitory effects of G. sylvestre were highly significant (P<0.001) at 6,12 and 24 hours, while that of tolbutamide at 24 hours. Aqueous extract of M.charantia and infusion of P. marsupium also produced significant inhibition of pituitary extract induced hypeglycaemia at 6^th and 24 hours, respectively.

4. Possible mechanism involved in the inhibition of the anterior pituitary hormone induced hyperglycaemia after the drugs has been discussed.

The author is thankful to the Dean, Gandhi Medical College, Bhopal, for providing facilities for this work and to Mr. M. C. variyar, for the statistical analysis of the data presented in the paper. He also wishes to thank M/s Bengal Immunity Co., Calcutta, for preparing anterior pituitary extract and to M/s Hoechst Pharmaceuticals Ltd., Bombay, for supplying Rastinon (tolbutamide) for the present investigations.

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