Studies on carbohydrate metabolism in rat kidney slices. III. Effect of adrenalectomy and hypophysectomy on glucose uptake and glucose formation

Studies on Carbohydrate Metabolism in Rat Kidney Slices.’ III. Effect of Adrenalectomy and Hypophysectomy on Glucose Uptake and Glucose Formation

62

CHING TSENG TENG

eight rats were used. Five more experiments on glucose formation from pyruvate by normal kidney slices have also been performed in addition to the three reported in a previous paper (1). In a previous study (1) it was found that kidney slices from alloxan-diabetic rats put out considerable amounts of glucose during slicing as well as during incubationin the absence of an added substrate. This was designated as glucose output. It was shown that after a 15-min. preliminary incubation, this glucose output was effectively removed as a source of error in the subsequent measurement of the disappearance of added glucose (glucose uptake) or the appearance of new glucose from added pyruvate (glucose formation) when the slices were flirther incubated for 1 hr. in fresh medium containing the desired substrate. This procedure has been followed in the present investigation. The results from the present and the previous experiments are therefore comparable. All animals had access to food and water up to the time of sacrifice. All incubations were carried out at 38°C. under an atmosphere of 95% OZ-5%CO2 . Other experimental details and methods of analysis have been described previously (1). RESULTS

Glucose Output and Glycogenolysis When properly fed, both the adrenalectomized and hypophysectomized rats maintained normal blood glucose levels ranging from 95 to 125 mg. %. They also showed normal leve,ls of kidney glycogen content, ranging from 2 to 5 pmoles/g. wet kidney. Glycogenolysis during the 15-min. preliminary incubation was negligible. Total glucose output during slicing and preliminary incubation was slightly below the normal average. These results are shown in Table I. Glucose Uptalce and Glucose Formation from Pyruvate (Table II) As compared with normal kidney slices, those from adrenalectomiaed rats showed essentially normal glucose uptake, but significantly decreased glucose formation. On the other hand, kidney slices from hypophysectomized rats showed considerably increased glucose uptake, but essentially normal glucose production. These changes in glucose metabolism in kidney slices due to deficiencies of the hormones of the adrenal cortex and the anterior pituitary are also in contrast with the changes due to alloxan-diabetes (which are manifested by both decreased uptake and increased formation of glucose to an extent apparently related to the severity of the diabetes), and with the changes following insulin treatment (which reduces glucose production and enhances glucose utilization). These observations have been reported previously (1). The comparisons are illustrated in Fig. 1.

CARBOHYDRATE

METABOLISM.

TABLE Glucose Output

III

63

I

and Glycogenolysis

by Kidney

Slices

Result,s on total glucose output during slicing and preliminary incubation :~nti those on glycogenolysis during preliminary incubation are expressed in micromoles of glucose/g. of wet kidney. Results on blood sugar arc expressed in mg.s,. GKxlIl Rats Blood sugar Glucose output Cl~C~gC~Ol~SiS Normal -0.2 5.1 90 ; -- 0 2 Adrenalectomized 112 :1,4 Hypophysectomized 3.0 -0.3 108 Y TABLE Glucose Uptake

II

and Glucose Formation

from Pyruvaie

by

Slice .v

Kidnq

Incubntion in all experiments preceded by a 15.min. 1)relimin:ary incubat,ioli Glucose concentration in incubation medium: 20 mmolcs,‘l.; pgruvate concentr:lt,ion: 40 mmoles/l. Each experimental vessel contained 0.2-0.5 g. of kidney slices in 2-3 ml. of medium containing either glucose or pyruvate as substrate. Results csprcssed in micromoles of glucose/g. wet kidney/hr.

Group I

Rats .-...-___

a I Sormal* Adrenalectomized j 9 Hypophysectomized

No. of observ.

Glucose formation

Glucose uptake Mean

S.E.

/

pu

JIem

S.E.

P”

~

8 -11.9 8 -11.5 8 1 -16.7

Zt 0.34 f 1.51 / >0.05 f 1.00 :
5.6 f 0.67 1 3.4 f 0.06 1 0.05

a Probability that the difference from group a is due to chance. * See Table V in a previous paper (1).

There is an abundance of clinical evidence that the hormones of the anterior pit,uitary and the adrenal cortex are diabet,ogenic when they are in excess. In addition, when they are deficient, hypoglycemia is likely to ensue and the patient is hypersensitive to insulin. It is generally agreed thatj the act’ions of these hormones on carbohydrate metabolism are antagonistic to that of insulin. It has become increasingly clear l,hat the action of insulin is twofold: the promohion of glucose utilization and th(l inhibit8ion of gluconeogenesis. This dual action of insulin has been demonstrat,ed in diabetic liver slices (2, 3), in intact diabetic animals (,a, 3), and in diabetic kidney slices (1). The data presented in this paper would appear to suggest that the adrenal cortex hormones are anti-insulin primarily wihh respect to glucose production, and have no significant

64

CHING

TSENG

TENG

g -10 5 -8 z -6----

t

18

FIG. 1. Bars above zero line represent mean values of glucose formation from pyruvate and those below line represent mean values of glucose uptake by kidney slices from various groups of rats reported in this and the preceding paper (1).

effect on glucose utilization. These findings are in agreement with the observations of other workers (6-9). With hypophysectomized rats, our results indicate that the anterior pituitary is diabetogenic mainly because of its action on glucose utilization. This is consistent with the observations of many workers on surviving rat diaphragm muscle (10-13). Our data also appear to suggest that the anterior pituitary has no significant influence upon gluconeogenesis. This is in keeping with the observations of Young (14), and with the current view of the action of the pituitary growth hormone (15). It is well known that following hypophysectomy the adrenal cortex will in time become atrophic. The present data appear to indicate that in hypophysectomized rats sufficient cortical function remains and a normal level of gluconeogenesis is maintained. The present data are at variance with the observations on rat liver slices by Renold and co-workers (3). They found that with liver slices from fed adrenalectomized and fed hypophysectomized rats neither glucose uptake nor glucose formation was abnormal. It should be noted

CARBOHYDRATE

METABOLISM.

III

ct;,

t.hnt t)he liver slice is a more complex system than the kidney slice. Fat example, the livers used by Renold and co-workers had relatively high glycogen corrtents and exhibited an active glycogen metabolism, whereas t.hc kidneys used in the present experiments had very low plgcogor Contents, and glycogenolysis, negigible as it was, was allowed to oc~~u~ cwnpletel; before l-he metabolic observations were made. These diffrrenws may acwunt~ for t,he differences in results wit#h liver nncl kidne!~ slices from ndrenalectomized and hypophysectomized rats. SUMMARY

‘l’ho upt~itke and format,ion of glucose by kidney slices from adrer ialwt omized and hypophysectomized rat,s have brtw studied. It. \V:IS I’c~utrd that thy effect of adrenalectomy was a sjgrriticant, reduction CI~ glucos~t format ion wit,hout changes in glucose uptake, and the cffec,t 01 lrypophysectomy was a marked increase of gh~conc uptake without signilicanl, c*hanges in glucose produ&on. These results have been cornpared with t’hose obtained with normal and dinbet ic ml s with ant1 wit-hout, prior insitlin treatment. REFERENCES