oe nae +

None-vf the reduced tolerance can be attributed to a shift in the
oxyhgmoglobin dissociation curve, In rats the curve ts shifted slightly
to the left, whereas in man there {8 a reported shift to the right.

Because propranolol impairs tolerance to hypoxia in experimental
animals, 1t {s important to assess {ts effects on human tolerance.
,



Technical Kepor! Documentetion Page

7. Goverment Ace!

3. Reciprent'« Catalog No.

-+

‘ond Subtitle:
| FECTS OF BROPRANOLOL ON TIME OF USEFUL FUNCTION i
UF) IN RATS, en ie
nena

pod
GF. Performing Organization Repprt Nom ~~

Tey] &. A] Mtggins, J M.] McKenzie, “ete //-"| 1]

Gi G. E.[Funkhouser,waed S$. R. Mullen : L - ef.

9. Pestoomnng Org exTFerrbTe Mame a 10. Work Umede (TRAIS)
\ | FAA Civil Aeromedical Institute
i P. 0. Box 25082 TI Contvort or Grant Ne.

Oklahoma City, Oklahoma 73125

TD. Type of Report ond Pernod Covered

12. Sponsqnng Agency Neme ond Address
Office of Aviation Medicine :
Federal Aviation Administration
800 Independence Avenue, S.W.
Washington, D.C. 20591

15. Supplementary Notes

ine Agency Code

This research was performed under Task AM-A-78-PHY-108.

-Avaivoet

to assess the effects of propranolol on tolerance to rapid decompression, a series
of experiments was conducted measuring time of useful function (TUF) in rats
exposed to a rapid decompression profile in an altitude chamber. In other experi-
ments TUF was measured for rats exposed to an oxygen/nitrogen gas mixture which
produced a hypoxic condition equivalent to that in the decompression experiments.

The findings were: (1) Rats become less tolerant to hypoxia of an onset rate
comparable to that of rapid decompression when given propranolol, and this intol-
erance is further exacerbated by an increase in physical exertion. (11) Younger
animals are more susceptible to this type of hypoxia, but propranolol has no
greater effect on hypoxia tolerance in younger animals. (iii) None of the reduced
tolerance can be attributed to a shift in the oxyhemoglobin dissociation curve.

In rate the curve is shifted slightly to the left, whereas in man there is a
reported shift to the right.

Because propranolol impairs tolerance to hypoxia in experimental animals, it is
important to assess its effects on human tolerance.

Th Key Words VE. Dratributvon Storement

Propranolol Document is available to the public
Altitude Tolerance through the National Technical Information
Rapid Decompression Service, Springficld, Virginia 22161.
Hypoxia : ;

19. Seeunty

Tel thre report) BW, Security Clessit, (ol thes paged Be Ne, et Pages | 22, Pree
Unclassified Unclassified ul
Form OOT F.1700.7 (8-72)

Reproduction of completed page outl



At the end of each experiment the rats were anesthetized with diethyl
ether, blood samples were drawn by means of cardiac puncture, and the
animals were killed. Serum propranolol measurements were made by the method
of Shand, Nuckolls, and Oates (20) as modified by Ayerst Laboratories. For
the gas-mixture series of experiments the oxyhemoglobin dissociation curves
of fresh samples of whole blood were measured (program A) on the Hem-0-Scan
Oxygen Dissociation Analyzer (American Instrument Company, Silver Spring,
MD).

III, Results.

The results of the TUF measurements for the decompression experiments
are presented in Figure 3 (23). The TUF for the younger rats was 11-12 s
shorter than for the older rats, regardless of the treatment administered.
This was a statistically significant difference (p<, 01). In both groups,
propranolol reduced the TUF by more than 25 s. This effect was significant
(p<, .01). Although the high dose produced a shorter TUF than did the low
dose for both groups, this difference was not statistically significant.

The results of the TUF measurements for the gas-mixture experiments
are presented in Figure 4 (22). Propranolol reduced TUF by 11 s in the gas-
mixture experiments (p = 0.057).

The average serum propranolol levels were 200 ug/L serum for the high
dose and 162 ug/L for the low dose. ns

The average 50-percent saturation point of oxyhemoglobin, expressed in
mm Hg, was 41.71 + 2.92 (SP) for saline-treated rats and 39.36 + 2.92 (SD)
for propranolol-treated rats. This difference was statistically significant
(p & -05) (23).

IV. Discussion.

In these experiments, propranolol significantly reduced the tolerance
of rats to hypoxic conditions of rapid onset. This effect, however, cannot
be attributed to a rightward shift of the ODC because the rats demonstrated

‘a statistically significant shift to che left, although the change (2.35 mm
Hg, a 5.6-percent decline) is probably not of great physiological
significance. The rats, therefore, are not suitable models for evaluating
the consequences of the rightward shift of the ODC that is reported to be
produced by propranolol.

t

It is possible that the reduced tolerance to hypoxia is not solely a
reflection of the f-adrenergic blocking effects of this drug. Bainbridge
and Greenwood (4) reported a tranquilizing effect for propranolol that
could not be attributed to a blockade of B-adrenergic receptors. Ln. their
study, the dextroisomer, which has practically no @-blocking properties, was
as effective a tranquilizer as the racemate. In another study by Trivedi
and Sharma (27) it was demonstrated that propranolol depresses the central

4


EF $ OF PROPRANOLOL ON TIME OF

USEFUL FUNCTION (TUF) IN RATS

I, Introductton.

Propranolol, a B-adrenergic blocking agent, is widely used for control
of cardiac arrhythmias, essential hypertension, and other medical conditions
(3,5,6,13,21,25,26,28). Because it has minfmal side effects (15,17,18), many
requests are being received by the FAA's Acromedical Certiffeation Branch for
approval of propranolol as a medicatton in the pilot group.

Several reports (1,11,12,14,16,19) have shown that propranolol shifts
the oxyhemoglobin dissociation curve (CDC) to the right, thus reducing the
oxygen transport capacity of hemoglobin. It has been suggested that this
effect, combined with the B-adrenergic blocking effects on cardiovascular

functions, might impair, altitude tolerance, particularly tolerance to a rapid
decompression.

To assess the effects of propranolol on tolerance to rapid decompression,
a series of experiments was conducted on male Sprague-Dawley rats, first
using the Civil Aeromedical Institute (CAMI) research altitude chamber for
rapid decompression profiles and subsequently using an oxygen/nitrogen gas
mixture to produce an equivalent hypoxke condition. .

Il. Methods.

Prior to the experiments, tests wore made with untreated rats, following
the decompression profile used in time of useful consciousness (TUC) studfes
of human subjects (7,8). This profile consists of: (4) rapid decompression
from 6,500 ft to 34,000 ft (2,000 to 10,400 m) In 26 s; (if) holding for 23 5
at 34,000 ft (10,400 m); (Lit) a descent at the rate of 5,000 ft/min (1,500
m/min). Because the rats did not lose useful Cunctfon with this profile, it
was decided to follow the profile only through the first minute of descent in

the. experiments on rats and to hold the chamber at 29,000 ft (8,800 m) until
toss of uscful function occurred.

To determine time of useful Cunetion (TUF), rats were placed inside a
double-compartmented clear plastic wheel (16 to [40.6 em] in'dfameter)
covered with aplastic mesh (Figure 1). The wheel was rotated at 1 revolu-
tlon per minute. Rotation was begun Tmin prior Co decompression and con
tinued until the rats were unable to walk within the rotating cage.

Two serfes of exper{ments were conducted using the decompression profile
desertbed above. ln the first sertes, 60 young mature rats (274 to 462 8)
wore used, Twenty rats received {atraperttoneal CP) injeettons of normal

{


ACKNOWLEDGMENTS

We would like to thank Dr. William R. Kirkham, Chief, Aviation
Toxicology Laboratory, for his advice and. for contacting Ayerst
Laboratories, New York, N.Y., which provided both the method and
the standard for the serum propranolol measurements.

We also gratefully acknowledge the assistance of Dr. Charles R.
Crane, Mr. Boyd Endecott, and other members of the Biochemistry
Research Unit, Aviation Toxicology Laboratory, for their assistance
in preparing the apparatus for measuring time of useful function.

We also thank Ms. S. Marlene Wicks, Mr. J. T. Saldivar, and
Mr. Russell Moses of the Aviation Physiology Laboratory for their
assistance in the data collection phase of this study.

pone



erdes of experiments with 40 rats (20 saline Created and 20
receiving the high dose of propranetol), an osygen/ni troge s mixture
(5.200 percent 05) was used to produce an equivalent hypoxte condition with=
out hypobarism, “Beeause of the Large volume of the rotating wheel, ft was
not possible to replace the chamber air with the gas mixture fn ca time short
enough to shautate the decompression profile. In order to matntaly the pro
file, an alternate method was used to moasure TUF, Rats were placed individ-
ually inside a clear plastic box (inside dimenstons of 4 in by 4 in by LO in
Figure 2), amt this box was retated 90° laterally at approximately 2-9
Intervals. Time was measured from. the beginning of the flushing per tod
untditthe rat was no longer able to maintain an upright posittou wher Che
box was rotated.

Ya another

Vine of useful funet ion (rE) apparatus ue
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g Mature Rats 276-3959
Propranolol Dose 0.00228 mg/g body weight

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Saline Propranolol
Figure 4,

Bargraph of mean and standard deviation. for time of useful function
(in sec) durin: cmixture experiments, (N-2 20, each group)

6



y Adolescent Rats 248-3219
Mature Rots 274-4629
Propranolol Low Dose 0.00114 mg/g body weight
Propranolol High Dose 9.00228 mg/g body weight
3
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Adolescent Mature Adolescent Mature Adolescent Mature
Rats Rots Rats Rots Rots Rats
Saline Treated Propranolol Propranolol

Low Dose High Dose

Figure 3,
pdard deviatton for time of useful function
Cin see) during decompression experiments. (N= 20, each group)

Bargraph of mean and st

5 -

2\


a

saline (control), 20 received E14 my propranolol hydrochloride per ky of

body Jeofght Clow dose), and the remaining 20 recetved 2.28 my per ky of body
weight, (igh dose). The high dose ts equivalent to a single 160-me dose for
a 70-ky man, the maximum recommended dose (15) for treatment of hypertension
(the maximam datiy dose is 640 my but divided into four equal doses). The
low dose is half this amount. Fer the second sertes of experiments, smaller
(248 to 321 4), Less mature animals were used Co determine df the effects
were consistent In different Jweight groups. All HP injections were admin-
istered approximately, 30 min before decompression.

Figure 1.
Time of usetal function (PEF) apparatus
used in decompression exper iments.


March ° 1979

Document is available to the public through the
National Technical Information Service,
Springfield, Virginia 22161

Prepared for
us. DEPARTMENT OF TRANSPORTATION
{Federal Aviation Administration
Office of Aviation Medicine
Washington, D.C. ‘20591

#9

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1

5.

8.

Agostinl, A., C. Berfascont, G. C. Gerli, M. Luzzana, and

L. Kossi-Bernardi: Oxygen Affinity and Electrolyte Distribution
of Human Blood: Changes Induced by Propranolel, SCIENCE,

182: 300-301, 1973.

Atkins, James M., and Lawrence D. Horo..t..  Cardfac Autonomic
Blockade in Exerci#ing Dogs, J. APPL. PHYSIOL.: Respirat.
Envfron, Exercise Physiol., 42:B78-883, 1977.

Atsmon, A., 1. Blum, M. Steiner, A, Latz, and Hl. Wijsenbeek:
Further Studies With Propranolol in Psychotic Patlents,
PSYCHOPHAKMACOLOGIA, 27:249-254, 1972.

Bainbridge, J. G., and D. T. Greenwood: Tranquilizing Effects
of Propranolol Demonstrated in Rate, NEUROPHARMACOLOGY,
102453-458, 1971,

Brachfeld, Norman: Metabolic Evaluation of Agents Designed to
Protect the Ischemic ee tanes and to Reduce Infarct Size,
AM. J. CARDIOL., 37:528-532, 1976.

Braunwald, Eugene, Ed.: Symposium on Beta Adrenergic Receptor
Blockade, In AM. J. CARDIOL. , 18(3):303-487, 1966.

Busby, Douglas E., FE, Arnold Higgins, and Gordon £. Funkhouser:
Effect of Physical Activity of Airline Flight Attendants on
Their Time of Useful Consciousness in a Rapid Decompression,
AVIAT. SPACE ENVIRON. MED., 47:117-120, 1976a,

Busby, Douglas E., E. Arnold Higgins, and Gordon E. Funkhouser:
Protection of A{rline Flight Attendants From Hypoxia Following

Rapid Decompression, AVIAT. SPACE ENVIRON. MED., 473942-944,
1976b,

Donald, David E., David A. Ferguson, and Sidney E. Milburn:
Effect of Beta-Adrenergic Receptor Blockade on Racing Performance
of Greyhounds With Normal and With Denervated Hearts, CIRC. RES.,
22:127-134, 1963.

Eurdich, W., fF. V. Schrijen, D. T. Krausman, P. Caldini, and
J. V. Brady: The fect of Beta-Blockade on Coronary and
Systemfe Circulation in Dogs at Rest and During Adaptation to
fxercise, ARCH. INT. PHARMACODYN,, 204:213-227, 1973.

o


24,

25,

26,

27,

28,

Snow, Do He, and Rd. Summers: The Acttons of the Beta=
Adrenoceptor Blocking Agents Propravotol and Metoprotol ti the
Maximally Exeretsed Worse, J. PHYSIOL. , 271:39r-40P, 1977.

Stenson, Robert EL, M.D. Flamm, Jr., Donatd C. Harrison, and
E,W. Hancock: Propranolet tn Hypertrophic Subsort te nosis,
AM. J. CARDIOL, , 31:763-773, 1973,

Tiveniua, Le, and G. Nyberg: Effects of Alprenolol aud
Propranolol on Ventilatory: Funct on, PHARMACOL, CLIN. , 2251-57,
1969.

Neuropharmacolog teal Studttes
oy 273753-758, 1973,

Trived!, G. 0, and RD. Shar
on Propranolol, UNDIAN J. MED.

Winkle, Roger A., Stanton A, Glantz, and Donald C, Harrisons
Pharmacologic Therapy of Yeatrteutar Arrhythmias, AM. J,
CARDIOL, , 36:629-650, 1925,

wd


28 owes
i

. OP?

ii?°

in.

hie



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nervous system, whereas another @ biocker, dichloroiseprenatine, {s an
excitant. In view of these findings, the depressant effects of -propranolol
must be included in any attempt to explain ita effects on the TUF,

Propranolol was not as effective in reducing the TUF when hypoxia was
induced by a mixture of gases, However, this difference may not have been
due to the difference tn barometric pressure in the two experiments. tt is
more likely explained by the difference in physical activity required by the
two methods of measuring TUF. The exercise level of the rats was consider~
ably greater during the decompression experiments than during the gas-mixture
experiments. This explanation is consistent with the report of Atkins and
Horowitz (2) who found that blockade of autonomle control of the heart in
dogs resulted in a diminished cardfac output during exercise by reducing heart
rate and myocardial contractile force, This effect on cardfac output was not
seen in the resting dog. Donald, Ferguson, and Milburn (9) reported the
effects of propranolol] on the racing time of normal -and cardfac-denervated
greyhounds. They found that the cardiostimulant action of sympathet {ie nerves
and circulating catecholamines were both important Co maximal performance.
Ehrlich et al. (10) reported that the vasod{lating etivity is
essential for an increased coronary flow during exercise.  Propranctol
increased the arteriovenous oxygen difference and did net diminish the cotal
oxygen consumption at rest and at the end of exercise, Snow and Summe:
reported that propranolol and metroprolol, another -8-blocking, agent,
decreased the racing performance of horses.

ss (24)

In light of the reports cited above, and our own observations regarding
differences tn the physteal demands of the protocols, we conelude that the
observed effects of propranolol were most Tikely duc to fahibitfon of pt
logical adjustments to exeredse and net due te any effects on the op
Furthermore, because both protocols {nvelved some degree of
not rule out the possibility that this effect on physfologteal responses is
the principal cause of the decrements in TUF observed in both expe §
It must be reiterated, however, that the ODC effects in aan may be
tant consideration, Therefore, a dec arding this f
the design and execution of safe trfals in homan subjects er on mo
able animal models.

fo-

V. Conelustons

Rats given propranolol are intolerant te hypoxta of an onset rate
comparable to that of rapid decompression, and this intolerance is further
exacerbated by an increase in physical exertion, :

Younger animats are more susceptible to this type of hypoxia, but
propranolol jhas no greater effect on hypoxta tolerance in younger animals.


14,

20,

21.

Fortler, Normand L., &. Michael Snyder, dirt Palek, and
Farle B, Wetas: Effect of Propranolol on Normal Numan
Erythrocytes, J. LAB. CLIN. MED, , 89341-50, 1977,

Humphrey, Stephen R., and Barry R. Alt
and Oxygen Delivery, AMOI. CARDIOL, &

Propranolol,
91-792, 1978.

Por

Raens, I, 0. Kuntzen, U. Techentrupp, and Me Dérner! The
Jafluence of Propranolol on Serum Gastrin Concent rat len and
Nydrochlorte Actd Secretion tn Renponse to Hypoglycemia in
Normal “Subject, DIGESTION, 13:193-200, 1975,

Lichtman, Marshal! A., Jules Cohen, Marton S. Murphy,

lzabeth A. Kearney, Aprtl As Whitheck: Effect of Propranolol
on Oxygen Binding to Nemoglobtn IN VITRO and IN Vivo,
CIRCULATION, 4)

1-886, 1974, :

Modell, Walter, Ed: Drugk of Choler 1970-1971, py. 41, 355,

36t-362, 364, 367-368, 379, C. V. Mouby, 1970,

Pendleton, Robert G., David I. Newmin, Sheldon S. Sherman,
Kdward G. Brann, and Wilttam BE. Maya: Effect of Propranolol
Upon the Hemog lob in-Oxygen Dissxocfatton Curve, J. PHARMACOL,
EXP. THER. , 180:647-656, 1972,

cet Inderat, ‘Thirty-second Edftion,
onomler, 1978,

# Acting on the Cardtovascular System,
+ Dukes, Ede: Meyler's Side Effects of Druga,
1975,

+ 8, pp. 442-444, Excerpta Medfen

Scheumpf, John D., David S. Sheps, Steven Wolfson, Alfred be
Aronson, and Lawrence S. Cob Altered Hemog lobtn-Oxygen
Afinity With Long-Term Propranolol Therapy in Patients With
Coronary Artery Diseae, AM. J. CARDIOL, 40276-82, 1977,

Shand, D. G., BE. M. Nuckolta, and 1, A, Oates: Ptanma
Propranolol Levels tn Adults, CLIN, PHARMACOL. THER. 1112-120,
1970,

Shopain, Baron, J
Malluctnat tons
1975,

Visual
10: 105-107,

ob Hirsch, and Samael ¢
nd Propranolol, BOL. PSYC

Slogel, Stdney: 7
Nonpars

+ Kolmogorov-smirnoy Two-Sample Test; In
fee, pp. 127-140, + 156,

Snedecor, George We, and WitTtam G. Cochean: "Student ts!
t-Hisertbutton, tn Stattatteal Methods, §
The Lowa State University Pre + lowa, 1967,

to

xth Edtt ton, pp. 59-62,