XIII, No. iJANUARY,
THE DIABETOGENIC HORMONE OF THE
BY DAVID SLOME.
(From the Department of Social Biology, the University of London, and the Buckston Browne Research Farm, Royal College of Surgeons of England.)
(Received June 26, 1935.)
(With Two Text-figures.)
NUMEROUS clinical observations have provided indirect evidence that the pituitary
gland exercises a significant effect on carbohydrate metabolism. Glycosuria is frequently a part of the acromegalic syndrome (Borchardt, 1908; Goetsch, Cushing and Jacobson, 1911). Houssay (1931) and Eidelsberg (1932) have emphasised that cases of acromegaly often manifest the symptoms and signs of diabetes.
The participation of the pituitary gland in the control of carbohydrate meta-bolism has been the subject of a most searching investigation by Houssay and his collaborators (Houssay and Biasotti, 1931a, b, c), who have conclusively established that the hyperglycaemia, glycosuria, acidosis and other diabetic manifestations, which follow excision of the pancreas in the toad, do not develop or develop only in a very mild degree if the animal has previously been hypophysectomised. This result was attributed to the secretion of a " diabetogenic " substance by the pituitary gland. Since it is possible in Amphibia to remove the anterior lobe of the pituitary gland alone, Houssay was able to demonstrate unequivocally that this "diabetogenic" substance is elaborated in the anterior lobe alone. Subsequent work by Houssay's school was carried out on dogs; but, as it is not possible in the dog to remove the separate morphological portions of the pituitary gland, the investigation was neces-sarily confined to indirect confirmation of the basic results obtained in amphibian experiments. Most of the experiments in this communication are based on the South African clawed toad (Xettopus laevis) and were reported at a meeting of the Society of Experimental Biology in December 1932. More recently a fresh supply of animals has made it possible to carry the enquiry to a further stage.
TECHNIQUE AND METHODS.
Hypophysectomy was carried out by the buccal route described by Hogben (1923). Using this approach, it is possible in Xenopus to remove (1) the anterior lobe, (2) the posterior lobe, and (3) the entire gland. The clear-cut effects on the chromatic function exhibited by toads after each of these provide independent con-firmation of the success of the operation. Pancreatectomy can be performed in a few minutes with the aid of an electric cautery without the loss of a drop of blood.
Blood glucose was estimated in o-i c.c. by the micro-colorimetric method described by Folin and Malmross (1929). The accuracy of the method was tested by estimating the glucose in a sample of blood and in a similar sample to which a minute known quantity of glucose was added. The added glucose was almost com-pletely recovered. For the withdrawal of blood the frog was pithed and the heart exposed by removal of the sternum and opening of the pericardium. The exterior of the heart was dried with absorbent cottonwool and the frog held in a horizontal position. The pendent heart was opened with scissors and the blood collected in a small crucible. About 0-5-1 c.c. of blood was thus obtained.
THE NORMAL BLOOD-SUGAR LEVEL.
It has now been firmly established that pigmentary effector activity in Amphibia is a delicate indicator of pituitary secretion. Xenopus laevis possesses a very striking capacity for colour change, predominantly determined by light reflected from the surface which occupies the field of vision, influenced only to a slight extent by tem-perature and ordinarily unaffected by humidity. In a white container the melanophores
are fully contracted in light and the animal is pale. In a black container they are expanded and the animal is dark. In darkness the melanophores are partially ex-panded and the animal assumes an intermediate hue. Total removal of the eyes or section of both optic nerves produces an intermediate condition of the melanophores. Complete hypophysectomy or removal of the posterior lobe alone results in loss of the normal black "background" response. The animals remain permanently an intensely pale colour. Removal of the anterior lobe, which also involves removal of the pars tuberalis, results in a permanent expansion of the melanophores, i.e. the normal response to a white " background " is lost. Colour response in Xenopus laevis and in all probability in other Amphibia is determined by two endocrine agencies. One of these (the " melanophore stimulant") is elaborated in the posterior lobe of the
N o .
1 2 3 4 5 6 7 8 9 1 0 1 1 1 2
Normal pale toads
Body weight in gm. 59 7 i 29 18 18 2 1 25 23 23 2 2 17 2 1
S e x
V i' + 3 a 3 3 3 3 6* Blood glucose mg. per 100 c.c. 22-7 2 0 9
2 r 6 27-9 21-0 27-1 28-3 27-3 3I -4 2S-3
2 0 7
Average blood sugar 25^4 ± 1 '02
Normal dark toads
N o .
! 2 Body-weight in gm. 16-0 21-5 1 2O-O 4 5 6 7 8 9 1 0 1 1 1 2 16-0 i8-5 23 23 17 2 0 16 I9-5 17 Sex 3 0 0 'i 3 3 3 0 1 0 Blood glucose mg. per 100 c.c. 26-5
2 9 8
The Diabetogenic Hormone of the Pituitary Gland 3
pituitary gland. The other endocrine agency is directly or indirectly associated with the pars anterior or pars tuberalis of the gland. In these experiments all animals from which the whole gland was removed showed characteristic pallor and all animals from which the anterior lobe (plus pars tuberalis) was removed showed maximum darkening of the skin.
The blood sugar of a series of twelve animals on a white background and of a similar series on a black background was first determined. The results are shown in Table I. A further series of blood-glucose determinations were carried out. The mean value for thirty-two normal pale toads was 25-6 mg. glucose per 100 c.c. and for twenty-one normal dark toads, 35-0 mg. glucose per 100 c.c. Thus the normal fasting level of the blood glucose of toads kept on a black background is significantly higher than that of toads on a white background.
THE EFFECT OF HYPOPHYSECTOMY ON THE BLOOD SUGAR. The blood-sugar level in twelve toads after total hypophysectomy and in a similar number after removal of the anterior lobe alone is set out in Table II. Including a further series of animals the mean value for twenty-two totally hypophysectomised toads was 23-8 mg. per 100 c.c. and for forty-one toads after removal of the anterior lobe alone 22-0 mg. per 100 c.c. These values are only slightly below those for the
N o .
1 2 3 4 6 8 <J io 11 12
S e x
Body weight in gm. 3° 3
£38 38 36 43 42 25 36 3« 33 36
Average blood glucose 22-8 ± 0 6 6
• Blood glucose mg. per 100 c.c. 26-3
2 1 7 2 0 3
2 0 6 2 1 6
27-4 2 I ' O 20-3 ±o-66
Removal of anterior lobe*
No. 1 2 3 4 S 6 7 8 9 1 0 1 1 1 2 Sex V V + <? 2 Body weight 27 27'S 35 26 28 25 4 6 26 23 25 2 0 2 0 Average blood glucose 20^5
Blood glucose mg. per
2 0 4
1 9 3
2 1 - 3 1 9 0
18-3 i8-3 24-9 ±°-55
• Seven months after operation.
Table III. Mean values of blood glucose.
Normal pale Normal dark
Total hypophysectomy Removal of anterior lobe
Number of individuals 32 21 22 41 Blood glucose mg. per 100 c.c.
2 5 6 35-0 23-8
normal pale controls. The blood sugar of well-fed hypophysectomised animals is within normal limits. If, however, the animals are fasting, a fatal hypoglycaemia rapidly develops.
EFFECT OF HYPOPHYSECTOMY ON SUGAR TOLERANCE.
Zwarenstein and Bosman (1932) have demonstrated an increased tolerance for glucose in the hypophysectomised toad. The blood sugar of a series of normal and hypophysectomised animals was determined at regular intervals after the injection into the dorsal lymph sac of 1 c.c. of a 2 per cent, aqueous solution of glucose per 30 gm. of body weight. A series of animals were used to determine each point on the curve. The results shown graphically in Fig. 1 show the manifest increased glucose tolerance of the hypophysectomised animal.
Fig. 1. Glucose tolerance curve.
EFFECTS OF PANCREATECTOMY ON THE NORMAL AND HYPOPHYSECTOMISED TOAD.
The Diabetogenic Hormone of the Pituitary Gland 5
Removal of the pancreas from toads from which only the anterior lobe (i.e. pars anterior + pars tuberalis) of the pituitary had previously been ablated is also not followed by the intense diabetes which develops after pancreatectomy. In a series of five such animals the mean blood sugar was 44-1 mg. per 100 c.c. 24 hours after pancreatectomy. The effect of pancreatectomy on the blood sugar of the hypo-physectomised and normal toad is illustrated graphically in Fig. 2.
The removal of the pituitary gland or of the anterior lobe alone therefore pre-vents or considerably modifies the development of the intense diabetes consequent upon experimental extirpation of the pancreas.
2 2 0
loo-•& 8 0 "
1 6 0
/ / a
1 i i i i i 9 12
15 18 21 24
Fig. 2. Effect of pancreatectomy.
and it accelerates the utilisation of glucose in the tissues. Furthermore it is believed to check the formation of glucose from protein sources in the liver. Pancreatectomy therefore effects a rise of blood by removing this inhibition of glucose formation from protein sources and by preventing the utilisation of glucose by the tissues.
The abnormally high blood sugar of the starved diabetic animal is derived from protein and fat sources. Animo-acids derived from endogenous protein are con-verted quantitatively to glucose. It is at this point that the diabetogenic hormone may exercise its effect. Removal of the anterior lobe of the pituitary effects a con-siderable reduction of the blood sugar of the starved diabetic toad. Thus a probable hypothesis, as postulated by Houssay, is that the hormone elaborated in the anterior lobe catalyses the formation in the liver of glucose from endogenous protein sources. If this hypothesis is correct, it seems reasonable to assume that the diabeto-genic hormone must also control the formation of glucose from exogenous protein. This aspect of the problem will be the subject of another communication.
1. The normal fasting level of the blood glucose of toads kept on a black back-ground was significantly higher than that of toads on a white backback-ground.
2. After hypophysectomy the blood sugar was within normal limits.
3. An increased tolerance for glucose was demonstrated after extirpation of the pituitary gland.
4. The diabetic manifestations which follow pancreatectomy in the normal toad did not develop or developed only to a mild degree if the toad had previously been hypophysectomised.
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