REGULATORY EFFECT OF TILE BLOOD GLUCOSE 
LEVEL ON THE SECRETION OF THE ADRENAL CORTEX* 
by 
G. L, Steeples, Jr., Gapt., li.C, and H. F. Jensen, Ph.D,, Chief Biochemist 
from 
Medical Department Field Research Laboratory 
Fort Knox, Kentucky 
1 January 1949 
under Study of Physiological Effects of Cold, Approved 
24 September, 1942, MDFRL Project Mo, 6-64-12-02-(7)* Project No, 6-64-12-02 
Sub-project MDFRL 02-(7) 
MEDEA 
1 January 1%9 
ABSTRACT 
REGULATORY EFFECT OF THE BLOOD GLUCOSE 
LEVEL ON THE SECRETION OF THE ADRENAL CORTEX 
OBJECT 
In the course of studies designed to determine the effects of 
hypothermia on the control of endocrine secretions it became necessary 
to know the effects of changes in blood glucose level on the secretory 
activity of the adrenal cortex. Alterations in the cholesterol content 
of the adrenals were used as indices of the activity of the gland. 
RESULTS AND CONCLUSIONS 
Hyperglycemia induced by oral administration of glucose produced an 
increase in the adrenal cholesterol indicating an inhibition of the adrenal 
cortex. After thirty to sixty minutes the adrenal cholesterol returned to 
normal values. 
Hypoglycemia induced by insulin injection produced a decrease in the 
adrenal cholesterol indicating a stimulation of the adrenal cortex. 
The role of the blood glucose level in the regulation of the secretion 
of insulin, on the one hand, and of epinephrine, on the other, is a possi- 
bility. 
RECOMMENDATIONS 
Similar experiments should be carried out using adrenodemedullated 
animals in order to determine whether the regulatory effect of the blood 
glucose'level is mediated through the anterior pituitary or through the 
adrenal medulla, 
Submitted by: 
G. L, Steeples, Jr., Capt., M.C, 
H. F. Jensen, Ph.D., Chief Biochemist 
Approved 
RAY GJpiffjS U U 
Director of Eesearc 
Approved^ 
FREDERICK J. KNOBLAUCH 
Lt. Col., 
Commanding REGULATORY EFFECT OF THE BLOOD GLUCOSE 
LEVEL OK THE SECRETION OF THE ADRENAL CORTEX 
I. INTRODUCTION 
Investigations in recent years have shown that the adrenal cortex 
plays an important role in maintaining the resistance of the animal 
organism to stress (l, 2). In view of this, any study assumes signifi- 
cance when it contributes to an understanding of the mechanism which 
regulates the secretion of this endocrine organ. It is now generally 
accepted that the activity of the adrenal cortex is controlled by the 
adrenocorticotrophic principle, which is secreted by the anterior pitui- 
tary.* The mechanism of the secretion of the adrenal cortex is, therefore, 
mainly associated with the factors influencing the release of the adreno- 
corticotrophic hormone by the anterior pituitary. Recently, it has been 
found that epinephrine plays an important role in the control of adrenal 
cortical activity and that this control is mediated through the anterior 
pituitary by bringing about a release of the adrenocorticotrophic hormone 
(1, 2). The manner by which epinephrine produces this effect is not known. 
Since epinephrine and the blood sugar level are so closely inter- 
related, experiments have been performed to determine whether the blood 
sugar level per se would influence the activity of the adrenal cortex. 
Alterations in the cholesterol content of the adrenals have been used as 
measures of elaboration of cortical hormones by the adrenal cortex. The 
changes in the cholesterol content of the adrenals observed on induced 
hyperglycemia or hypoglycemia are presented. 
II. EXPERIMENTAL 
A. Lethods and Procedures 
White adult male rats of the V/istar and Sprague-Dawley strains 
weighing between 225 to 2B0 grams were used. The animals were starved 
overnight but allowed water. 
1. Oral Administration of Glucose: The rats were intubated with 
a catheter and 2 ml. of a 50 per cent glucose solution were introduced by 
means of a hypodermic syringe into the experimental and 2 ml. of distilled 
water into the control animals. After certain time intervals, the animals 
were killed by the guillotine method. The adrenal glands were immediately 
dissected, weighed and analyzed for cholesterol according to the method of 
Schoenheimer and Sperry (4). The total cholesterol was determined in each 
case and the amount of cholesterol is reported as mgra. per 100 ngm. of 
fresh wet adrenal tissue. Blood sugar determinations were carried out 
* Deane, Shaw and Greep (3), have presented evidence that at least in the 
rat, the secretion of the electrolyte-regulating hormones of the adrenal 
gland is not under the control of the anterior pituitary. according to the procedure of Somogyi (5)» 
It was found that handling and intubation of the animals led to a 
variable "alarm" reaction, as indicated by a decrease in adrenal chicles- 
terol. For this reason, it was essential to accustom the animals to 
the experimental conditions before use. This was done by passing a fine 
rubber catheter into the stomach twice daily for about eight days. Only 
healthy, growing rats are suitable for studies of adrenal cholesterol 
changes inasmuch as inanition or infection markedly influences the 
adrenal cholesterol levels. The animals were kept as much as possible 
in a constant temperature environment. 
2. Administration of Insulin: The experimental animals were 
injected subcutaneously with 0,5 I.U. of insulin while the control ani- 
mals were injected subcutaneously with 0.25 ml. of saline solution. The 
adrenal cholesterol and blood sugar levels were determined ninety minutes 
after administration. 
III. RESULTS AND DISCUSSION 
Table 1 illustrates the mean cholesterol changes in the adrenals 
as well as the mean blood sugar changes determined simultaneously in rats 
after oral administration of 2 ml, of a 50 per cent glucose solution in 
water. Oral administration of glucose produced a distinct increase in 
the adrenal cholesterol and an elevation of the blood sugar level half an 
hour after administration. Between thirty to sixty minutes, there was a 
sharp decline in the adrenal cholesterol content to normal levels. The 
increase in the adrenal cholesterol level, observed at thirty minutes, was 
significant inasmuch as the lowest values for cholesterol found at that 
time were definitely greater than the highest values obtained in the con- 
trol animals. 
Elmadjian, Freeman and Pincus (6) found that oral administration of 
glucose (l ml. of a 50 per cent solution) to rats produced a lymphocytopenia 
within one to two hours aftesr administration. We also observed a decrease 
in lymphocytes after oral glucose administration at a time at which the 
cholesterol levels of the adrenals were normal. The fall in lymphocytes 
is supposed to indicate a stimulation of the adrenal cortex and would seem 
to contradict the finding of an increase in adrenal cholesterol level. 
However, this may be explained by observing that the apparent inhibition 
of the adrenal cortex was of short duration and that a drop to normal in 
the adrenal cholesterol occurred within thirty to sixty minutes after 
glucose administration. The cholesterol content was normal after one hour, 
indicating an actual outpouring of adrenocortical hormones, thus account- 
ing for the observed lymphocytopenia. Dohan and Lukens (?5 reported that 
intraperitoneal injection of glucose into rats produced a decrease in the 
ascorbic acid content of the adrenals, determined thirty-five to sixty 
minutes after glucose administration. Abelin (£) observed that, seven to 
eight hours after oral glucose administration (l gram per 100 grams of 
body weight) to rats, a reduction of about twenty-five per cent in the 
adrenal cholesterol occurred. In repeating Abelin1s experiments, similar 
results were obtained. TABLE 1 
Mean Changes in the Cholesterol Content of the Adrenals and in the 
Blood Sugar Levels in Normal Flats After Glucose Administration. 
Number 
of 
Animals 
Type of 
Experi- 
ment 
Time of 
Sacrifice 
After 
Injection 
(minutes) 
Weight 
of Fresh 
Adrenal 
Glands 
(mgra.) 
Cholesterol Blood Sugar 
Content per Level at 
100 mgm. of Termination 
Fresh Adrenal (mgm. %) 
Tissue 
(mgm.) 
18 
Controls 
(2 ml. H20) 
■*«- 
35 
3.44 4 0.10 
72 
12 
Glucose* 
30 
34 
4.91 f 0.16 
81 
12 
Glucose 
60 
36 
3.30 4 0.13 
99 
12 
Glucose 
120 
36 
3.83 4 0.11 
90 
7 
Glucose 
240 
34 
3.57 4 0.09 
— 
8 
Glucose 
300 
36 
3.21 4 0.11 
70 
4 
Glucose 
360 
34 
3.70 i 0.07 
* 2 ml. of 
through 
’ 50 per cent 
a catheter. 
solution introduced by 
a hypodermic syringe 
** The animals were sacrificed at 
the same time 
intervals as 
the 
glucose injected rats 
intervals• 
i. The results are averages for all 
time 
Since hyperglycemia led to an increase of the adrenal cholesterol 
content, investigation was directed toward the determination whether hypo- 
glycemia would effect a lowering of the adrenal cholesterol. In order to 
ascertain the effects of hypoglycemia, rats were injected subcutaneously 
with 0.5 I.U. of insulin per animal. 
Since the subcutaneous injection per se resulted in some adrenal 
stimulation, the values obtained with insulin injections should be compared 
with those obtained in the control animals which were injected subcutaneously 
with 0.25 ml. of saline solution. As can be seen from Table 2, the choles- 
terol values of the saline injected controls were lower than those of animals 
receiving no treatment. This finding indicates again the importance in any 
study of adrenal functional activity of the employment of control animals 
which have received handling and treatment similar to the experimental 
animals. TABLE 2 
Mean Changes in the Cholesterol Content of the Adrenals and 
in Blood Sugar Levels in Normal Eats After Injection of Insulin. 
Number 
of 
Animals 
Type of 
Experi- 
ment 
Time of 
Sacrifice 
After 
Injection 
(minutes) 
Weight 
of Fresh 
Adrenal 
Glands 
(mgm.) 
Cholesterol 
Content per 
100 mgm, of 
Fresh Adrenal 
Tissue 
(mgm.) 
Blood Sugar 
Level at 
Terrains tion 
(mgm. %) 
5 
Control 
Uninjected 
90 
35 
2.82 4 0.03 
72 
a 
Control 
0.25 ml, 90 
Normal saline 
32 
2.61 4 0.16 
66 
la - 
Insulin 
(0.5 I.u.) 
90 
32 
2.04 4 0.11 
20 
As can be seen from Table 2, insulin induced hypoglycemia effected 
a stimulation of the adrenal cortex as indicated by the lowered adrenal 
cholesterol level. This finding is in agreement with that of Qershberg 
and Long (9) who observed a fall in the adrenal ascorbic acid and with 
that of Vogt (10) who found a depletion in the adrenal lipids of rats 
following insulin injection. 
The findings reported here support the assumption that hyperglycemia 
leads to a diminished release of epinephrine by the adrenal medulla with 
a correspendingly lessened stimulation of the anterior pituitary, which 
then causes an inhibitory effect on the adrenal cortex as indicated by an 
increase in the cholesterol content. In hypoglycemia, the reverse takes 
place, 
It appears that the blood sugar level regulates the secretion of 
insulin (hyperglycemia, stimulation; hypoglycemia, inhibition) on the 
one hand and the secretion of epinephrine (hyperglycemia, :- inhibition; 
hypoglycemia, stimulation) on the other. Epinephrine, in turn, regulates 
the level of functional activity of the adrenal cortex; this effect is 
mediated through the anterior pituitary. It appears that epinephrine not 
only influences the secretion of the adrenocorticotrophia principle, but 
also the elaboration of the thyrotrophic hormone. The investigations of 
Rawson and his associates (ll), and of Soffer et al. (12), indicate that 
epinephrine affects the rate of hormone output of the thyroid; this in- 
fluence also being mediated through the anterior pituitary. It is well 
recognized that the physiological functions of insuli# are in general antag- 
onistic to those elicited by the hormones of the adrenal cortex and thyroid. Whether or not the regulatory effect of the blood glucose level on 
the secretion of the adrenal cotex and of the thyroid is directly 
mediated through the anterior pituitary or indirectly through the adrenal 
medulla is not as yet established. Experiments similar to those reported 
here, carried out in adrenodemedullated animals, might give an answer to 
that question. 
IV. CONCLUSIONS 
Hyperglycemia induced by oral administration of glucose in rats 
caused an elevation of the adrenal cholesterol level indicating an inhi- 
bition of the adrenal cortex. 
Hypoglycemia induced by insulin injection in rats produced a decrease 
of the adrenal cholesterol level indicating a stimulation of the adrenal 
cortex. 
The role of the blood glucose level in the regulation of the secre- 
tion of insulin, on the one hand, and of epinephrine, on the other, is 
a possibility. 
V. PECO* 1P3«D.\TIQMS 
It is recctfomended that similar experiments be carried out in adreno- 
demedullated animals in order to determine whether the regulatory effect 
of blood glucose is mediated through the anterior pituitar:/ or through the 
adrenal medulla. 
VI. BIBLIOGRAPHY 
1, Long, C. N, K, The conditions associated with the secretion of 
the adrenal cortex, F©deration Proc. 6: 461, 1947- 
2. Sayers, G. and R. A. Sayers. The pituitary-adrenal system, in 
Recent Progress in Hormone Research. Mew York, Academic Press, 
Inc. 2: 81, 1948. 
3. Deane, H, V/,, J. H. Shaw and R. 0. Creep. The effect of altered 
sodium or potassium intake on the width and cytochemistry of 
the zona glomerulosa of the rat*s adrenal cortex. Endocrinology, 
43: 133, 1948, 
4. Schoenheimer, R. and W, Sperry, A micromethod for the determina- 
tion of free and combined cholesterol, J. Biol. Chem. 106: 745, 
1934. 
5. Somogyi, H. Determination of blood sugar. J, Biol. Chem. 106: 69, 
1945. 
6. Elmadjian, F., H, Freeman and. G. Pincus. The adrenal cortex and 
the lymphocytopenia due to glucose administration. Endocrinology 
39: 293, 1946. 7. Dohan, F. D, and F. D, V7* Lukens. Experimental diabetes pro- 
duced by the administration of glucose. Endocrinology 42: 244, 
1948. 
8. Abelin, I. Zur Frage der Beteiligung der Nebenniere am Zucker- 
stoffwechsel. Helvet. physiol, pharm. acta. 3: 71, 1945* 
9. Gershberg, and C. N. H. Long. The activation of the adrenal 
by insulin hypoglycemia. J. Clin. Endocrinol. 8: 587> 1948. 
10, Vogt, M, Cortical lipids of the normal and denervated supra- 
.renal gland under conditions of stress. J. Physiol. 106: 394, 
1947. 
11. Rawson, R, Personal communication. 
12. Coffer, L, J,, M, Voltera, J, L. Gabrilove, A. Pollack and 
M. Jacobs. Effect of iodine and adrenalin on thyrotropin in 
Grave’s disease and in normal and thyroideeternized dogs. 
Proc. Soc. Sxper. Biol. & Ued. 64: 446, 1947.