SALT AND WATER DISTRIBUTION IN HEREDITARY AND IN INDUCED HYBQTHA%EA%&~IC DIABETES INSIPIDUS

IN THE RAT

SYDNEY hl. FRIIXIMAN AND CCPNST,IN('E L. FKIEDMAN Department of Anatomy, U.~tizler.sity of British Colzkmbiu, l[/izncoua~er, British Columbia

Received February 24, 1'36.7

Abstract Salt and. water ~netabolisiaa and the distrihutioii of N a , K, and water in

gaatrucaiernlus and in aorta were measured in spont;ineous hereditary hypo- thalamic and i11 s~lrgirally induced diabetes illsipidus in the rat. The degree of *everit11 in the two types of the disease was estimated in ternas of salt aiid water handling. IVater turnover in 24 lno~irs was about equal to body weight in the hereditary clisease and about 6096 of body weight in the induced disease. Skefetal imuscle N a inc.re;xsed inore than 20:4 in the fanmilial disease, and the gain involved both cells and environ~nent. There was 110 correspondilrg loss of K. Similar cbhariges of lesser degree were nc~ted i11 the induced disease. 'The degree of Ka accumulatior~ appears to be partially dependent on the duration of the disease.

Introduction k'altin and Schroetier have recently bred a strain of rats (Krattleboro)

\\.it11 hereditary hypothalamic diat~etes insipidus (1). The disease arose as an apparently spontaneous inutatiori in a. strain of Long-Evans hooded rats being bred for purposes unreliltcd to the diabetes. Beccause our stu<Iies of the integrated role of the n e u r o h ~ ~ ~ > o ~ ~ l ~ ~ - s i s and adrenal cortex in the control of salt and water balance depend on the exainlination of conditions in deficiency states, we asked for a small supply of these animals and this request was generously met.

I'reviously it- has only been possihlc to study diabetes insipidus in anim:ile surgically deprived of neurohypophyseal function by stalk sectlola or bly lesions in the hypothalanlus (2, 3, 4). The present report is concerr~ed with a coin- parison of salt and water rnetat)olism and distribution in the spontaneous hereditary- diabetes ineipidus of the Brattleboro strain and in the induced diabetes insipidus prodrnced by a single stereotaxic lesion placed in the nledian enainence to interrupt the s~ipraoptico-h ypophlrseal tract.

Methods Twelve female rats with hereditary diabetes insipidus and an equal nunaber

of their Long-Evans controls were provided by Dr. Valtin. The diseased ani~nals and seven controls were 10 months of age and five controIs were 7 months old a t the time we received them. Pitressiia tannate in oil (1 unit) nTas administered subcutaneously to the polydipsic rats prior to air shipment; \vitIl this treatment all animals arrived in good shape. T~nmediately ~iptsn receipt, the r-1nimals were placed in individual cages, and except during- the met:abolism tests to be described, remained there without being disturbed until terrninatioi-a of the experiments 22 days later.

Canadian Journal of Physiology a11d Pharnracology. Volume 43 (1965)

699

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700 CANADIAN JOURNAL OF I'HYSIOLOGY A S D PHARMACOLOGY. VOI,. 43, 196.5

Stereotaxic lesions as previously described (2) were placed it1 the nlediall eminence in thirty 4-month-old female rats of an inbred Wistar strain, of specific pathogen-free derivation, on the day of receipt of the test animals. At the end of 2 weelcs, the 12 rats with the highest water intake were selected from this pool. 'Together with 12 controls matched for weight, these animals served as the experimental groups for the comparisons t o follow. As before, all ailiillals were individually housed. During the third week, all four groups, the tm-0 with either spontaneous or induced diabetes and the two matching control groups, were placed in individual metabolislrrl cages. Water intake and output and the urinary co~lcentrations of sodium and potassium were measured over three consecutive 24-hour periods t o estabIish uniforrn conditions and then for a fourth period in which food intake was also measured. This part of the study was intended t o characterize the pattern of salt and water handling in diabetes insipidus and t o provide an indication of the relative severity of the disease in the two forms.

The experinnents were terminated 22, 23, and 24 days after receipt of the animals. Conventional methods for the study of the distribution of sodium, potassiunn, and water in gastrocnemius and aorta samples were used. These methods have been described in detail elsewhere (5). In brief, the procedure began with bilateral nephrectomy with the animal under anesthesia and the intravenous injection of carefully ineasured a~llounts of inulin. 'Three hours later, blood samples were taken, and this was followed a t once by the excision of gastrocnenlius saniples. Rapid excision of the abdominal aorta concIuded the procedure.

Results Fduid Uulnnce and Electrolyte Excretion

The results obtained on the fourth day of the salt and water nletabolisnl study are presented in 'Table I. As VaItin and Schroeder originally pointed out, hereditary diabetes insipidus can be described in unequivocal terms. The animals ingest an amount of water equal to, and often in excess of, their own body weight. The output of urine is correspondingly high. These animals d o not lose extra water in the urine onIy, however, but by other routes as well. Thus, control animals used about 5 m1/100 g of water and the diseased animals about twice this amount apart from urine. The osmolarity of the urine was greatly reduced as is evident fro111 the fact that the concentrations of both sodium and potassium in the urine were a t vanishingly low levels. Although the bulk loss of these ions was aIso higher in diabetes insipidus, this can be accounted for by an increased food intake. More potassium than sodium was lost, bu t this occurred in all four groups and reflects the food composition (powdered F'urina rat chow, 180 meq of Na, 260 meq of K per kg). Despite the higher intake of food, the diabetic animals did not keep up with their meta- bolic requirements, since they were Ieaner than their controls.

Salt and water ~~letabolism in the animals with induced diabetes insipidus differed only in degree. Thus, water intake and urine output were high, again with about twice as much water used, apart from urine formation, as in the

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FRIEDMAN ANI) FHIEUMAN: SALT rZNU WATEK DISTRIBUTION IN DIABE'H'ES 701

TABLE I

Indices of salt and water metabolism measured during a 24-hour period in hereditary and in recently induced diabetes insipidus

- - - - - -- - -- -- -- -

Hereditary Iilduced Control diabetes Control diabetes

(Long-Evans) insipidus (iiistar SPF) insipidus -

LYater intake, ml/100 g

Urine output, ml/100 g

Water output/ intake, %

IJrirse [Na], meq/liter

Urine [MI, meq/liter

Urine Na loss, meq/100 g

lirine K loss, meq/l00 g

?Food intake, d l 0 0 b'

iVater/food, y l /g

il'erght No. oi rats

l l f 1

* f values = standard error. $Food contains 180 meq Najkg and 260 mecl Kikg.

controls. A higher nletabolic requirement was again indicated hy an increased food requirement and a failure even so t o maintain a full growth rate. Again, urinary sodium and potassiuns concentrations were very low even though the total amount of sodium and potassium lost was increased.

Conlparison of urine volume and urinary sodiurrl concentration in Fig. % characterizes the difference in degree between the two fornss of diabetes

Urine Volume mv100g 24 hr Urine [ ~ o ] meq/liter

I I

200

Induced

100

0

I . 1. Changes in urine volunie and urine [Na] as indices of severity i11 hereditary and induced diabetes insipidus. Values are averages oi four comseeutive 24-hour periods.

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702 CAXADIAN JOURNAL C7F PHYSIOLOGY AN11 PHAKhlihCO1,OGY. VOL. -13, 1965

The distribution of water, Na, ancB K in hereditary and in recently iriduced diabetes insipidus

- - -- - - -- - - - -- - -

I leredit,try Induced Goritrol di'ibetes Coritrol diabetes

(Long-Evaiis) insipidus (IAJistar SIPI;) insipicl~as

l'ldsm'l ECE'V, rri1/100 g [Ka], mecl/iiter I!<!, mecl/liter LC Na, rnecg/lO0 q 1SC K, nnec1/100 g

Rlrnscle (gastrocnemius) ECFV, ml/kg ffww Ceil wdter,

ml/kg ffww 'l'ot'el water,

ml/hg fflvw Na,, rneq/l;g ffww N;i,, rrleq/kg ffww 'I'otnl Na,

ruecl/kg ffww I~itrac.ellular Na,

ixieq /liter I<,,, meq/kg ffww I< ., rneq/kg ffww 'I'otal K,

n~eq/kg flww l utrncellular K,

rnecl/liter ,lcrrta

Total watcr, nilikg ffu cv

Total Na, nleq/kp fiww

Total K, rncq/lrg ffuw

\!-eight, g ha). o f rats

So,~r:: f values - standard error; I<CI:V = extraccllul:~r fluid volume = inul i i~ spar?; &:(.I = estracrllular; ffww = fat-free wet weight. NaG = F:CFVms& X 0.9ti [NsTplnsm:l. Nai = 1Jatotul - Nao.

* p < 0.02. tfi < 0.06.

insipidus. I t must be renaembered, however, tha t the i~lciriced form of the disease had been present for 3 weeks a t the very most.

Results of the ion partiti011 stud)- are shown in Table II. 'The ch:tnges n-hic.11 u-e have previously described in diabetes illsipidus (2) were all easily defined in tlie a~limrgls m-ith the hereditary disease. Thus s o d i u ~ l ~ concentration iam the plasma rose, and, since the extracellular fluid voluiaae was, if anything, in- creased, tlmere was a real rise in tlae total anlount of circulating extracellular soc%ium. A small fall in plasma potassium wrls recorde(1, and even though this is frequently not significant in any one experiment, i t has been regular-117 otl- served. Presunaably this reflects sirlmple dilution in an cxpanded extracella~lar fluid volurne.

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PKIEDMAN ANY FKIEDMAK: SALT A N D WATER H)ISTKTBUTION IN DIABETES 703

In skeletal muscle the ntost obvious change in the hereditary disease was an irlcrease in the total amount of sodltlnl in the tissue. Althougls to a liinited extent this was due to a higher environmental sodiurrl conccntration, there was also a real inc.rease in the a ~ n o u n t of cell sodium. No siyraific;int change in the distributio~-a of water in skeletal muscle was observed. If there was :a c1irection:il trend, however, i t was from cells t o envirorlinent and hence parallel to that indicated by the plasma analysis. No change in the amount or distribtltion of p~6tassiu111 was found.

iZ similar pattern of change was 01)servcd in the animals with intluced diabetes, although once again this wits considerably less in degree. The accnnlu- lation of sodiuln in n-auscle in the two groups with diabetes insipidus is coinpdred in Fig. 2 with that observed in a recent si111ilar experiment terininated 44 days

Fac,. 2. Changes irl totaI and "intracelf~ahr" Na i r n rat gastrocrlernius in~lscic in relation to the duration of diabctes insipidus. (I) Ijiabetes illsipidus 24 days after lesion; ( 2 ) diabetes insipidus 44 days after lesion; (3) hereditary diabctes insipidus sf more than 1 year's duration.

after placcnicnt of the lesion. I t appears tha t degree may be related to dur, d t ' 1011. The directly measured total v~~lrres for water, Na, 311~1 K suffice t o char;tc-

t-erize the few changes observeci in aorta. Thus ininillla1 Na acc~linulr~tion was observed and is worth mentioning o~ l l y because i t was in the same direction as in muscle. A real increase in I(, necessarily intracellul:ir, was also noted.

Discussion Hercciitarjr h~~potha lamic diabetes insipidus in the Brat t leboro strain is

characterized, as described by Valtin and Schroeder (11, by :L water turnover of the order of the animal's own body weight. This evidently involves a good deal of meta1)olic work, for even though inore food was ingested the animals

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'904 CANADIAN JOURNAL OF PHYSIOLOGY AND PIIARMACOLOGU. VOL. 43. 1965

remained leaner than the normal controls. Much of this work may be accounted for by the need to warn1 the ingested water to body temperature. Presumably, too, the continual need t o drink kept the animals restless.

A consequence of the higher food consuinption was an increase in the bulk output of sodiunn and potassium in the urine despite the reduction in their concentrations. Like the original authors, we found that more potassiun~ than sodiunl was eliminated in the urine. This occurred in all groups, however, and, in the main, reflects the conlposition of the food. No explanation for tlne enlarged deficit between water intake and output can be attempted since this study was not designed t o provide full metabolic data.

In terms of the distribution of salt and water in the body, hereditary diabetes insipidus was characterized by an accumulation of sodium, seemingly without ,a corresp~nding loss of potassium. Indeed, in the aorta, potassium was frankly increased. The extra sodium was in part contained within the inulin-accessible extracellular spaces of the body and in part withiin cells as well, a t least in skeletal muscle, the bulk tissue of the body. In association with this, the whole body extracellular fluid volun~e increased, seemingly a t the expense of cell water.

There docs not seem to be any real difference between the hereditary form of diabetes insipidus and that which can be produced by an appropriately placed stereotaxic lesion. Even though in the latter case the disease was less severe, the basic features of the pattern both in terms of the handling and of the distribution of salt and water were essentially similar. Even the failure t o measure a shift of water from cells t o environment in the present experirrlent cannot be considered a point of difference, for such a water shift has, a t other times, been measured in induced diabetes insipidus in both the rat and the dog (2, 6).

There is a strong suggestion that the accumulation of sodiunl in diabetes insipidus is a continuous process, so that its degree depends on the duration of the disease; experiments are in progress t o test this point further. We have elsewhere shown that this accumulation of sadiurtl is due negatively t o the absence of vasopressin and positively to the unopposed action of mineralocorti- coids (7, 8, 9). This does not imply that the level of adrenal mineralocortical function is increased but only that i t is in this case unopposed by posterior pituitary hormones. Lichtwitz et ad. (6, 10) have also reached a similar con- clusion from their studies in the dog. The usefulness of chlorothiazide i~n diabetes insipidus t rea t~ne~nt (11) is consistent with the view tha t this is a salt-retaining syndrome.

Acknowledgment 'I'his work was supported by a grant from the Medical Research Council sf

Canada. References

1. H. VALTIN and 11. A. SCHHOEDEK. Am. J. Physiol. 206, 425 (1964). 2. S. M. FRIEDMAN, H. F. SCMERRER, M. NAKASHIMA, and C. L. FRIEDMAN. Am. J. Physiol.

192, 401 (1958).

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FRIEDMAN A N D FRIEDMAK: SALT AND WATER DISTRIBUTION IN DIABETES 705

3. I . C. JONES. In The neurohypophysis. Edited by II. Heller, Butterworths, Lotldon, 1957. p. 253.

4. G. C. KENNEDY, H. S. LIPSCOMB, and P. HAGUE. J. Endocrinol. 27, 345 (1963). 5. F. A. SRBTEK and G. Woo. Am. J. Physiol. 205, 1290 (1963). 6. A. LICHTWITZ, D. I-IIOCO, and M. L~ELAVILLE. Ann. Endocrinol. (Paris) 16, 811 (1955). 7. S. M. FRIEDXAN, F. A. S R ~ T E R , hl. NARASHIMA, and C. I,. FRIEDMAN. Am. J. Physlol,

203, 697 (1962). 8. S. M . FRPEDMAN, F. A. S K ~ T E R , RT. NAKASHIMA, and C. L. FRIEDMAN. Am. J . Physiol.

203, 702 (1962). 9. S. M . FRIEDMAN, F. A. SKBTEK, hTa NAKASHIMA, and C. L. FRIEDMAN. Am. J. Physiol.

203, 709 (1962). 10. A. LICHTWITZ, D. HIOCO, and M. BELAVILLE. Ann. Endocrinol. (Paris) 16, 819 (1955). 11. 6. C. KENNEDY and J. D. CRAWFORD. J. Endocrinol. 22, 77 (1961).

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