Pharmacological Research Communications, Vol. 17, No. 6, 1985 501

SKIN PENETRATION OF MINERALS IN PSORIATICS AND

GUINEA-PIGS BATHING IN HYPERTONIC SALT SOLUTIONS

Shani, J.l, Barak, S.', Levi, D.l, Ram, M.I, Schachner, E.R.*,

Schlesinger, T.3, Robberecht, H.3, Van Grieken, R.3 and Avrach, W.W.4

'Dept. of Pharmacology, The Hebrew University School of Pharmacy, POB 12065,

Jerusalem; 2 Asaf Harofe Hospital, Tzrifin; 3 Soreq Nuclear Research Center,

Yavne; 4 Dept. Chemistry, University of Antwerp (UIA), B-2610 Wilrijk, Belgium

and 4 Dept. of Dermatology, Hadassah-University Hospital, Jerusalem, Israel

Received in final form 15 Februarv 7 985

SUMMARY

Penetration of electrolytes through the human skin was measured in

healthy volunteers and in psoriatic patients after bathing in the Dead-Sea

or in simulated bath-salt solutions. Significant increases in the levels

of serum Br, Rb, Ca and Zn were noticed only in the psoriatic patients

after daily bathing in the Dead-Sea for a 4-week regimen. Guinea-pigs

"bathed" in simulated Dead-Sea bath-salt solutions containing radionuclides

of Ca, Mg, K and Br. Traces of each radionuclide were detected in the

blood and in some internal organs after 60 minutes of bathing. The

radionuclides showed a physiological pattern in their organ distribution.

Even though the whole investigation was carried out in hypertonic

solutions, there is a definite penetration of salts through healthy (human

and guinea-pigs) and damaged (psoriatic) epidermis. This finding suggests

that improvement of the psoriatic condition after bathing in the Dead-Sea,

may be partly attributed (in addition to ultraviolet irradiation) to the

minerals' effect on the psoriatic skin.

0031-6989/85/060513-l 2/$03,00/O 0 1985 The Italian Pharmacological Society

502 Pharmacological Research Communications, Vol. 17, No. 6, 1985

INTRODLICTION

Our interest in penetration of minerals from hypertonic salt

solutions into the human circulation emenates from investigating possible

medical effects after bathing in the Dead-Sea. The Dead-Sea contains

300-320 g/l salts, of which KCl, MgC12, CaC12 and NaCl are the major ones

(98% of the dried salt). The other two percent consist of bromide salts,

heavy metals, trace elements and solids.

The balneo-therapeutic properties of the Dead-Sea have been known

throughout the centuries, and have been documented since King Herod's time,

but the first modern medical report on the effect of heliobalneotherapy at

the hot spring of Zohar (Ein-Bokek) on psoriasis was published by

Dostrovsky and Sagler only in 1959. Since then, various reports on

improvement of psoriasis after bathing in the Dead-Sea have been published

(Avrach, 1977a; Avrach, 1977b; Avrach & Niordsen, 1974; Montgomery, 1979),

and a review on the medical properties of the Dead-Sea was published by

Drugan in 1976 (6). The most recent study analyzed results in 1,631

patients who had stayed at Ein-Bokek under careful medical control for 4

weeks, 95% of them showing marked improvement (Montgomery, 1979). Because

of the high rate of success in elimination of psoriatic plaques after

bathing in the Dead-Sea, groups of psoriatic Danes came to the

International Psoriasis Treatment Center (IPTC) in Ein-Bokek for

climatotherapy, and one of those groups participated in our study.

Psoriasis is a complex proliferative skin disease, showing partially

uncontrolled nonmalignant growth of the epidermis. Its etiology is

unknown, but is apparently related to imbalanced cyclic nucleotides.

Pharmacological Research Communications, Vol. 17, No. 6. 1985 503

In such a case. a treatment for psoriasis should to a large extent be

via the circulation, supplying some elemental ions for CAMP production.

This aspect was studied for sodium, potassium (Hodgson, 1960), copper

(Lipkin et al, 1962), selenium (Abboud, 1978) and bromine (Shani et al,

1982). Moreover, psoriasis has been treated successfully by salt

combinations both externally (Justesen & Harkmark, unpublished) and

internally (Troitskaia, 1965), and it was suggested that a possible

mechanism of the latter treatment (NaBr administration) is partially via

the known sedative effect of bromide on stress-induced psoriasis. We

undertook to study whether and to what extent minerals are capable of

penetrating the skin from an hypertonic solution as occurs in the Dead-Sea.

MATERIALS AND METHODS

Twenty-four healthy Israeli volunteers (12 males and 12 females,

20-48 years old) and 21 psoriatic Danes who came to Ein-Bokek for

climatotherapy of their disease (10 males and 11 females, 16-60 years old),

participated in this study. The healthy Israelis were divided into four

groups of 6 each and bathed once only, for 30 minutes, either in the

Dead-Sea or in 1.5%, 5% or 15% Dead-Sea bath-salt solutions, prepared by

redissolving the dried Dead-Sea mixture and heating it to 37°C. Blood was

withdrawn from their cuboidal vein before and immediately after bathing,

after cleaning the area with water and then with 70" ethanol. Blood was

withdrawn under similar conditions from the psoriatic Danes immediately

after their arrival in Israel, again after their first 30-minute bathing,

and once again after a 4-week stay in Ein-Bokek. All blood samples were

left to clot at room temperature for 1 hour, the clot detached from the

tube with a thin wooden applicator and the samples left refrigerated

overnight for better separation. After decantation, 4-5 ml of each

504 Pharmacological Research Communications, Vol. 7 7, No. 6, 1985

untreated serum was used for bromine determination by a conventional

wavelength-dispersive X-ray fluorescence (XRF) (Shani et al, 1982) and

additional 250 p aliquots were dried on a Mylar film and used for

determination, in threshold, of Sr, Rb, Se, Fe, Ca, K, Zn and Cu, by an

energy-dispersive XRF procedure (Roberecht et al, 1982). Sera were also

analyzed for Na, Mg and Cr by Perkin-Elmer model 403 atomic absorption

spectrophotometer, and Cl was titrated on a Radiometer model CMT-10

chloridometer. All participants consented to the

Helsinki agreement. Significances of differences

and after bathing) were calculated by the Student

"Sabra' albino guinea-pigs, 250-300 g each,

experiment. Four radioisotopes of ions existing

in the Dead-Sea were used: 47 Ca (Amersham), 28Mg

study according to the

for all 5 groups (before

s "t" test.

were used for our second

n significant quantities

BNL), 42K and 82Br

(Soreq). Four groups of guinea-pigs were used for studying the penetration

of each isotope: cycling, males, pregnant and lactating, 9-12 in each

group. The guinea-pigs were carefully shaven, then injected IP with sodium

pentobarbital 30 mg/kg and immersed, except for their heads, in a 37°C

water-bath containing 15% Dead-Sea bath-salt solution with lo/.&i/l of each

radionuclide. After 60 minutes of bathing, the guinea-pigs were taken out

of the water-bath, rinsed under the tap, bled and decapitated. Liver,

spleen, lungs, heart, brain, stomach, small intestine, skin, bone and

kidneys were taken from all animals. Uteri and ovaries were taken from

cycling guinea-pigs, testes from the males, placenta, amniotic fluid and

fetus from the pregnant females. Milk was squeezed from the lactating

mothers, from whom the pups had been removed the night before. All organs

were sampled, weighed and counted. CPM/g and organ-to-blood ratios were

calculated for all organs sampled.

Pharmacological Research Communications, Vol. 17. No. 6, 1985 505

RESULTS

Elemental analysis of human serum revealed significant penetration of

four ions through the psoriatic skin, and only penetration of one ion

through the healthy skin, after bathing in the Dead-Sea for one month and

30 minutes respectively (Table 1). No increase in the levels of any of the

ions measured was detected in the healthy volunteers after their 30-minute

bathing in the simulated bath-salt solutions (Table 1. 1.5% salt solution

not shown). The ions elevated in the sera of the psoriatic patients after

one month of daily bathing in the Dead-Sea were Br, Rb, Ca and Zn. Even

though the serum was concentrated before its analysis, and the detection

limits were low (0.06 - 4pg/l), only 9 elements could be analyzed by XRF

and 4 by atomic absorption. Further lowering of these detection limits by

a factor of 10 could not have made it possible to determine more elements

(Robberecht et al, 1982).

Analysis of penetration of radionuclides through the guinea-pig skin

demonstrate that the same radionuclide accumulate in the same internal

organs in all four groups studied - pregnant, lactating and cycling

females, as well as in the mature males. Of high significance were the

following elemental retentions: 47 Ca concentrated over 270-fold in the skin

and significantly also in the bone, spleen, milk and ovaries; 28Mg

concentrated in the skin, ovaries, spleen, heart and bone; 42 K was absorbed

in the skin, and found its way to the bone, ovaries, spleen and amniotic

fluid, while 82 Br concentrated in the skin, testes and bone, but not in the

spleen (Table 2-results for pregnant and lactating animals not shown).

Some sporadic uptake was noticed for some of the radionuclides in other

organs, i.e. 42 K in uteri of cycling animals and 82 Br in pregnant

guinea-pigs' ovaries. Organ-to-blood ratios (CPM/g organ over CPM/g blood)

below 3 were not considered meaningful. In some cases a certain

Table

1.

M

easu

rable

se

rum

el

ectro

lytes

(m

ean+

SEM

)

afte

r ba

thing

in

the

Dead

-Sea

or

in

simu

Elem

ent*

Heal

th

Isra

eli

Volun

teer

s :n

=6)

Psor

iatic

Da

nes

(n=2

1)

and

5.0%

Sa

lt So

lution

15

%

Salt

Solut

ion

Dead

-Sea

30

m

in

Afte

r Af

ter

Afte

r 4w

its

un

it Be

fore

Af

ter

Befo

re

Afte

r Be

fore

Af

ter

Arriv

al 1

Bath

Ba

thing

Sr

m

gll

0.5k

O.l

0.6i

O.l

0.3k

O.O

0.3k

O.O

0.3+

0.0

0.4k

O.O

0.42

0.0

0.4k

O.O

0.4+

0.0

Rb

mg/

l 0.

6iO.

l 0.

650.

1 0.

4to.

1 0.

3kO.

O 0.

620.

1 0.

7kO.

l 0.

6kO.

O 0.

7kO.

l 1.

1+0.

1t

Se

mg/

l O.

l+O.

O 0.

1+0.

0 O.

l+O.

O 0.

1~0.

0 0.

1+0.

0 0.

1+0.

0 0.

1+0.

0 O.

lkO.0

O.

l+O.

O Br

wm

lO

kO.8

lO

k1.1

lO

k1.6

12

k1.8

lO

k2.3

8.

7i1.

8 3.

5kO.

2 4.

3kO.

3 9.

4*0.

6-k

Fe

rvm

4.

1kO.

8 3.

2kO.

5 2.

9kO.

8 3.

2kO.

4 1.

9i0.

2 2.

4kO.

3 3.

4kO.

4 2.

8kO.

2 3.

4kO.

5 Ca

wm

70

29.0

69

k6.8

69

k4.1

67

26.3

68

f1.4

73

+2.5

t 71

k2.3

7O

k2.3

75

+2.6

1-

Zn

wm

1.3k

O.2

1.3k

O.l

0.8iO

.O

l.O+O

.l 1.

OkO.

l 0.

8kO.

O l.O

+O.O

1.

OkO.

O 1.

4kO.

l t

cu

wm

l.OkO

.2

l.O+O

. 1

l.OkO

.1

1.01

rO.l

1.0+

0.1

l.O?O

.O

1.2i

o.o

1.1k

O.l

l.l+O.

O

Na m

eq/l

137k

1.6

136k

2.9

145k

1.6

1432

2.0

129k

4.4

13Ok

7.4

137k

2.3

134k

1.9

139k

8.0

Mg

w/l

23k2

.4

22k1

.4

21kO

.9

21kO

.9

2h1.

8 21

k1.9

22

k1.5

22

k1.6

20

21.3

Cl

meq

/l 93

k1.3

96

+2.5

95

k5.0

97

k3.7

97

k6.0

lO

Ok9.

2 99

55.6

lO

lk7.6

96

k4.5

Cr

p/l

1.8k

O.2

1.9L

O.2

0.8k

O.2

0.7i

O.2

l.OkO

.6

0.7k

O.4

l.OkO

.2

1.5k

O.4

l.OAO

.3

* K

valu

es

were

re

jecte

d as

th

e se

ra

were

sli

ghtly

ha

emol

ytic,

wh

ich

incre

ased

th

eir

pota

ssiu

m

leve

ls

t=

p co

.05

in he

alth

y Is

rael

is an

d ps

oria

tic

Dane

s,

befo

re

and

ated

ba

th-s

alt

solu

tions

at

va

rious

co

ncen

tratio

ns

Table

2.

Or

gan-

to-b

lood

ratio

s (m

ean+

SEM

) of

47

Ca,

28M

g,

42K

and

82 B

r pe

netra

ting

thro

ugh

the

skin

of

guine

a-pig

s af

ter

imm

ersio

n fo

r 60

m

inut

es

in 15

%

Dead

-Sea

ba

th-s

alt

solu

tions

at

37

"C,

E

cont

aining

10

yC

i/l

of

each

tra

cer

(n

= 9-

12).

Orga

n 47

Ca

Cycli

ng

Mal

es

28M

g 24

K Cy

cling

M

ales

Cy

cling

M

ales

0.9+

0.3

0.9k

O.3

l.O+O

.* 3.

4iO.

6

8.6k

1.6

13.0

21.8

10

.0+2

.4

4.2k

1.2

1.6k

O.4

1.8k

O.3

4.2i

l.O

2.9k

O.6

3.6k

O.8

3.9A

O.8

5.3k

l.l 4.

OkO.

6

2.1i

0.3

l.lLO.

3 1.

4fO.

4 1.

2kO.

3

1.5k

O.4

1.3k

O.4

2.2k

O.3

3.Ok

O.3

0.8k

O.2

1.6~

0.3

2.1k

O.l

3.4k

O.5

8.9f

l.O

7.9k

1.9

17.8

k3.1

11

.6+2

.9

10.5

k2.5

4.

9kO.

8 11

.3k2

.0

8.9k

l.O

1.2i

o.2

0.5k

O.l

2.Ok

O.3

3.Ok

l.O

3.1k

O.7

---

9.6k

l.O

---

20.7

+3.5

---

35

.1+8

.3

---

82Br

Cy

cling

M

ales

Liver

Splee

n

Lung

s

Hear

t

Brain

Stom

ach

Small

In

test

ine

Skin

Bone

Kidn

eys

Uter

us

Ovar

ies

Test

es

0.4k

O.l

7.45

1.1

2.2k

O.2

1.4k

O.2

0.92

0.2

1.22

0.3

3.1k

O.4

104.

7+20

11.9

k1.4

0.9k

O.2

2.3k

O.4

6.05

1.0

---

0.5k

O.l

6.1k

1.6

3.8~

0.8

2.8k

O.3

2.7k

O.4

0.95

0.4

3.Ok

O.5

338.

0*44

33.8

~6.4

1.12

0.6

3.2k

1.2

---

3.6k

O.4

---

3.42

0.4

0.3k

O.O

0.7*

0.3

F 0.

3kO.

l 0.

8~0.

1 $

0.4k

O.l

0.7k

O.l

.G

1.2-

ro.2

1.

2kO.

3 2 ?

0.75

0.2

0.2i

o.o

.9

l.OtO

.2

1.Ok

O.l

B 0.

4kO.

l 0.

6iO.

l

27.1

k1.2

13

.7rt4

.8

6.6*

1.8

4.7k

1.3

0.6k

O.l

0.82

0.1

0.7k

O.l

---

2.0*

0.4

---

---

5.4i

l.O

508 Pharmacological Research Communications, Vol. 17. No. 6, 1985

radionuclide concentrated differently in the same organ excised from

different animal-groups. These findings deserve further investigation.

DISCUSSION

Assuming that the therapeutic effect of the Dead-Sea is in part due

to its minerals' content, clinical effectiveness studies of bathing in it

were focused on the ability of its various minerals to penetrate through or

into the epidermis. This is a slow process as the intact stratum corneum

is limiting percutaneous absorption, and minerals are extremely insoluble

in lipid membranes and their transport via the intercellular route is

limited.

The questions raised in this study are whether one can expect

measurable penetration of minerals through the skin after only a short

(30-60 minutes) bathing in a salt solution?, and so is there any difference

in penetration between psoriatic and healthy human skin?

As to the first question, there are varying views regarding the

lag-time needed for ionic species to penetrate into the circulation.

According to Tregear (1966a,b), 24Na, 32Br and 32P begin to penetrate the

skin within 10 minutes of their application and dynamic equilibrium is

reached by 50 minutes. Our study in guinea-pigs demonstrate that after 60

minutes of bathing the whole body in the salt solution, and having a

sensitive measurement system (radioisotopic counting), the concentration of

the various elements in blood and body tissues could be measured with high

accuracy and reliability (Robberecht et al, 1982).

This study also demonstrates that penetration of Dead-Sea minerals

via psoriatic skin is more profound than through a healthy skin (Table 1).

It is well established from clinical experience that absorption is

increased through damaged skin, and that a skin injury comparable to eczema

Pharmacological Research Communications, Vol. 17, No. 6. 1986 509

is most simply induced experimentally by stripping (Tregear, 1962). We

believe that in the psoriatic skin, with its abnormal capillary dilatation

and damaged stratum corneum, penetration rates are higher because of the

partial lack of protection of the damaged stratum corneum. An additional

factor which enhances minerals' penetration into the psoriatic skin is the

frequent use by the patients of a keratolytic ointment (i.e. - salicylic

acid 3-5x) and vaselin. The latter base is known to increase the

permeability of the stratum corneum 4 to 5 fold, as it can then take 4

times its weight of water (Blank & Scheuplein, 1969).

Permeability of the skin in different mammalian species varies

remarkably (Van Dilla, Tregear, 1966a. The differences between the human

and animal skin is paralleled by the differences in their electrical

conductance, but the difference in permeability between the various ions in

the same species is not significant (Tregear, 1966a). If any

generalization is at all possible, it would seem that human skin is more

impermeable then the skin of a mouse or a guinea-pig, and that guinea-pig

skin may in some cases serve as useful approximation to human skin testing

its permeability (Wahlberg, 1968a; Scheuplein & Blank, 1971). This is the

reason why, in our studies, absorption through guinea-pig skin was measured

by radionuclides, but penetration of the Dead-Sea minerals through human

healthy and psoriatic skin was measured by non-radioactive methods - XRF -

and atomic absorption. At worse, the penetration of Dead-Sea minerals

through guinea-pig skin will be an overestimation of what is occuring under

similar conditions in the human.

In a series of papers Dubarry demonstrated (Dubarry et al, 1971,

1972; Tamarelle & Dubarry, 1972) that the maximum penetration of the ions

through skin was observed when the solute had low salt rather than high

510 Pharmacological Research Communications, Vol. 17. No. 6, 1985

salt, and that the more concentrated the external solution is, the less

penetrable through the skin are the ions soluble in it. Significantly less

1311 penetrated the skin from a 30% NaCl solution than from 3% or 1% NaCl

solutions, but the amount which penetrated was still measurable in all

three concentrations. Similar experiments were carried out by Giberton and

Cohen (1970).

Extensive studies on this aspect were carried out by Wahlberg et al

since 1962. These authors noted that the relative absorption of 51Cr

through the guinea-pig skin increased with increasing chromium

concentration to a maximal absorption of 4%, and when the concentration was

further increased, the absorption decreased to about 1%. The absolute

absorption also increased with increasing chromium concentration, but at a

certain concentration a plateau was obtained (Wahlberg & Skog, 1963;

Wahlberg, 1968a). The same finding was confirmed later for "SrC12

(Wahlberg, 1968b) : a relative absorption of about 3% and an increase in

absolute absorption with increasing concentration. Wahlberg also showed

that the absorption of " SrC12 was of the same order of magnitude as that

observed for other metal elements previously studied, and it seems that the

same applies to the various elements of the Dead-Sea (Wahlberg, 1973;

Wahlberg & Skog, 1963).

In conclusion, inasmuch as ions do penetrate the human skin, their

absolute penetration values after bathing in the Dead-Sea brine are low.

Our previous paper (Shani et al, 1982) describes higher concentration of

bromine in skin of Dead-Sea workers and in psoriatic patients after a

longer stay on the Dead-Sea shore. We suggest that this element also

enters the body through breathing and drinking. The quantities of other

elements that penetrate are apparently too low to be measured or to induce

a pharmacological effect. It also seems reasonable to conclude that

Pharmacological Research Communications, Vol. 17, No. 6, 1985 511

psoriatic skin is more penetrable to most elements, and that some

penetration may occur even if diluted Dead-Sea waters (i.e. - various

conentrations of the Dead-Sea bath-salt solutions) are used. The optimal

concentration of these salt solutions, and the length of time for bathing

in them to insure maximal absorption and penetration through the human skin

are still to be investigated.

ACKNOWLEDGMENTS

This work was supported in part by the Dead-Sea Works Ltd., Israel, by the Israeli Health Resorts Authority and by the Joint Research Fund of the Hebrew University and Hadassah. The authors acknowledge the comments of Dr. D. Albin. H. Robberecht acknowledges support from the Belgian Ministry of Health and from the Israeli-Belgian Cultural-Exchange Program.

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