Investigative Ophthalmology
October 1975
782 Reports
search carried out at BNL under contract with
the United States Energy Research and Development Administration, and supported in part by
Grant CA 16316 from the National Cancer Institutes. Submitted for publication May 29, 1975.
"For earlier papers in this series see: Lambrecht,
R. M., and Wolf, A. P.: The ] - 2 Te («, 3n)
i--<Xe -» "31 Generator, Radiat. Res. 52: 32, 1972.
REFERENCES
1. Bulpitt, C. J., Dollery, C. T., and Kohner, E.
M.: The marginal plasma zone in the retinal
microcirculation, Cardiovasc. Res. 4: 207,
1970.
2. Flower, R. W.: Infrared absorption angiography of the choroid and some observations on
the effects of high intraocular pressures, Am.
J. Ophthalmol. 74: 600, 1972.
3. Oosterhuis, J. A., and Barker, R. B.: Ocular
fundus fluorometry, Proc. Int. Fluorescein
Angiography, Albi, 1969, Basel, 1971, Karger,
pp. 52-54.
4. Pilkerton, A. R.: Infrared choroidal absorption
curves in humans, Ophthalmol. Res. 5: 41,
1973.
5. Riva, C. E., and Ben-Sira, I.: Injection method
for ocular hemodynamic studies in man, INVEST. OPHTHALMOL. 13: 77,
1974.
6. Hoccheimer, B. F.: Angiography of the retina
with indocyanine green, Arch. Ophthalmol.
86: 564, 1971.
7. Lambrecht, R. M., and Wolf, A. P.: Cyclotron
and short-lived halogen isotopes for radiopharmaceutical applications, in: Radiopharmaceuticals and Labeled Compounds, 1: 275,
1973.
8. Ansari, A., Atkins, H. L., Lambrecht, R. M.,
et al.: '-''I-indocyanine green ( r - 3 I-ICG) as
an agent for dynamic studies of the hepatobiliary system. IAEA-SM-185/61. In: Dynamic
Studies with Radioisotopes in Medicine, 1:
111, 1974. Also see references therein.
9. Lambrecht, R. M., and Wolf, A. P.: Cyclotron production of radiohalogens and their
use in excitation labeling. Intern. Symp. on
Radiopharmaceuticals, Atlanta, Georgia, Feb.
12-15, 1974. (To be published in Radiopharmaceuticals, Chapter 11. Society of
Nuclear Medicine, New York, 1975.)
10. Packer, S., Redvanly, C. S., Lambrecht, R. M.,
et al.: Quinoline analog labeled with iodine123 for melanoma detection, Arch. Ophthalmol. 94: 504, 1975.
11. News Report in Chemical and Engineering
News, pp. 20, October 1, 1973.
Standardized aerobic and anaerobic exercise: differential effects on intraocular
tension, blood pH, and lactate. R. A.
KIELAR,
P.
TERASLINNA,
D.
G.
ROWE,
AND J. JACKSON.
The effects of standardized aerobic and anaerobic exercise intensities on intraocular tension,
blood lactate, and pH were studied. Intraocular
tension decreased rapidly at all exercise intensities.
The absolute lowest level of intraocular tension
reached with aerobic and anaerobic exercise levels
varied by only 1.5 mm. Hg and this difference
was not statistically significant. Blood lactate and
pH changes correlated with intraocular tension
changes at anaerobic exercise levels, but not at
aerobic exercise levels. These findings associated
with aerobic exercise have not been previously reported. It is suggested that parameters other than
the decrease in blood. pH and. the increase in blood,
lactate are responsible for most of the decrease in
intraocular tension associated with dynamic exercise.
Previous studies have revealed that dynamic
exercise will invariably decrease the intraocular
tension. 13 It has been reported that the intraocular tension reduction is directly related to the
exercise load3- ' even though the exercise intensities have not been standardized to the individual subjects. In none of the studies that investigated the roles of blood pH and lactate during exercise were the exercise loads standardized
as to the degree of aerobic and anaerobic involvement of each subject. This investigation was thus
undertaken to determine the effects of specified
intensities of aerobic and anaerobic exercise on
the intraocular tension of healthy trained male
athletes, and to attempt to explain the possible
efleets using determinants of the relative anaerobic
load, namely blood lactate and blood pH.
Methods. Seven male athletes were used as
subjects in this study. Exercise tests were performed on a bicycle ergometer at maximum
(anaerobic), 80 per cent maximum (anaerobic),
and 60 per cent maximum (aerobic) loads. A
Schi0tz tonometer with a plunger weight of 5.5
grains was used to measure the intraocular tension (IOT). The average time between tests in
each individual .subject was twelve days.
The initial work load for the maximum test
was established at 200 Kg. per minute. The load
was increased by 200 Kg. per minute at the end
of each minute and the subject rode until he
reached exhaustion. The heart rate and IOT measurement were taken at rest and within one
minute after termination of maximal exercises,
and again at the end of each subsequent minute
of recovery during the first five minutes and then
at ten minutes of recovery.
Blood pH and lactate measurements were taken
at rest, and within one minute after termination
of maximal exercise, and again at five and ten
minutes of recovery.
For the submaximum tests 60 and 80 per cent
of the difference between the average resting and
maximum heart rate for each subject were calculated. These values were then added to the subject's resting heart rate and the sums represented
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Reports 783
Volume 14
Number 10
the designated percentages of his maximum performance. A Heart Rate Controller was used to
maintain these predetermined heart rates during
submaximuin tests. The total length of submaxim u m exercise was 10 minutes. The average
length of maximal exercise was nine to ten minutes depending upon the individual subject.
In the 60 per cent test the initial work load
was set at 400 Kg. per minute. The Heart Rate
Controller was used to increase the heart rate
automatically by increasing the work load until
the individually prescribed heart rate was reached.
During exercise the work load was automatically
increased or decreased when needed to maintain
the prescribed heart rate. The first submaximuin
bout lasted five minutes at the end of which the
subject assumed the supine position on the table
and the measurements described previously were
taken within one minute; an additional 15 seconds
were allowed for the subject to remount the
bicycle. The second bout was performed like the
first. At the end of the second five minutes of
exercise the subject again assumed the supine
position and recovery measurements were taken
as described after the maximum test.
The procedures used in the 80 per cent test
were the same as in the 60 per cent test with the
exception of the initial work load which was 700
Kg. per minute, and the work heart rate which
was 80 per cent of the difference between resting and maximum.
Statistical methodology. The means and standard deviations were calculated for IOT, blood
pH, and blood lactate concentration at each load
intensity and measurement time. A two-way analysis of variance with subjects repeated across the
intensity of exercise stress and the time of measurement was employed to determine if any significant differences existed between the means due
to the intensity of exercise, time of measurement,
or an interaction of intensity and time. The 0.01
level was utilized for all tests of statistical significance.
Results. With maximum exercise, the heart rate
rose from a baseline of 60 to 180 and returned
rapidly to 130 one minute after exercise. With the
80 per cent exercise load, the heart rate rose from
a baseline of 57 to 160 and returned rapidly to
100 one minute after exercise. With the 60 per
cent submaximal exercise load, the heart rate rose
from a baseline of 60 to 135 and returned rapidly
to 80 one minute alter exercise.
Changes in blood pH, lactate, and IOT with
the various exercise intensities are tabulated in
Tables I through III.
Comparison of IOT with different exercise
loads. There was an increasing drop of IOT with
increasing loads (Table I ) . The lowest level of
IOT reached with different exercise loads varied
only by 1.5 mm. Hg (Table II). At 10 minutes
after exercise, the IOT remained lower with in-
Table I. Comparison of changes in IOT, pH, and
blood lactate in the various exercise intensities
(average of 7 subjects)
Difference between
rest and cessation
of exercise
IOT (mm. Hg)
pH
Blood lactate
(mg./c.c.)
Exercise intensities
Maximum
60%
-4.30 -6.35
-0.09 -0.26
-3.70
+0.1
+ 17.2
+52.0
+76.5 (96.5*)
"Five minutes after exercise.
Table II. IOT (mm. Hg) before and after various
exercise intensities (average of 14 eyes)
Exercise intensities
Time of measurement
Resting
End
1-2 minutes after
10 minutes after
11.65
7.95
7.60
10.4
80%
Maximum
11.65
7.85
6.70
9.80
13.2
6.85
6.10
7.5
Table III. Comparison of changes in blood pH
and lactate in various exercise intensities
(7 subjects)
Difference between
rest and 10 minutes
after exercise
pH
Blood lactate
Exercise intensities
Maximum
+0.03
+ 7.3
-0.04
+40.4
-0.22
+ 88.6
creasing exercise intensity (Table I I ) . None of
these above changes, however, were statistically
significant.
Comparison of lactic acid with different exercise intensity. There was increasing blood lactic
acid concentration with increasing intensity of
exercise (Table I ) . The increase in lactic acid
concentration at the 60 per cent exercise level
was very minimal, and thus indicated that at this
intensity the exercise was almost entirely aerobic.
Comparison of phi with different exercise loads.
There was no change in the pH at the 60 per cent
intensity level (aerobic exercise), but at anaerobic
levels (80 per cent and maximum) there was an
increasing drop of pH with increasing intensity
of exercise (Table I ) .
Discussion. Rhythmic or dynamic exercise is
characterized by short periods of contraction
which alternate with periods of relaxation. In
dynamic exercise there is a unique set of patterns
of cardiovascular and metabolic response which
can be categorized as to the intensity of the work.
These patterns can be described as follows:"' (1)
A nearly alactacidemic level of exercise performed
in a perfect respiratory and humoral state. There
are no changes in blood pH. This exercise pattern
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784 Reports
occurs in aerobic exercise. The 60 per cent submaximal test done in this study would correspond
to this level. (2) A more severe level of exercise
with considerable lactacidemia, performed in a
respiratory steady-state. However, the respiratory
exchange ratio increases and compensatory alveolar hyperventilation occurs, decreasing the
arterial P(;o., below 40 mm. Hg. There is a slight
drop in blood pH. This would correspond to
moderate anaerobic exercise levels and the 80 per
cent submaximal level test used in this study
would approximate this level. (3) A high work
level with considerable lactacidosis and hyperventilation increasing in an irresistible manner.
The work must be interrupted in a state of extreme acidosis and exhaustion. The respiratory
exchange ratio exceeds 1.0 and arterial PCOo falls
below 30 mm. Hg and the pH below 7.25" The
maximal exercise test done in this study would
correspond to this level.
The selection of the submaximal exercise loads
in our study was based on the information that
about 60 per cent increase of the possible heart
rate response to exercise elicits about 50 per cent
of the maximum oxygen uptake capacity, which
can be performed without anaerobic involvement.0
The 80 per cent test was then selected to be in
the midpoint of 60 per cent and maximum performance.
It is quite apparent that at all levels of work
load in this study, there was a rapid decrease in
intraocular tension during the first few minutes of
dynamic exercise. This has been demonstrated
previously by authors using various work loads.1"3
This decrease has been postulated to be due to
the osmotic effect of increasing lactate and dehydration and decreasing pH which results in
hyposecretion of aqueous.-' "
At anaerobic work levels (80 per cent and
maximum tests) changes in blood lactate and
pH were correlated with changes in intraocular
tension. These findings are consistent with changes
in lactate and pH found by other investigators.-- ~
The increase in blood lactate and decrease in pH
changes associated with decreased intraocular
tension with exercise noted by previous investigators, however, have bsen done using nonstandardized exercise levels with no attempt to compare
standardized aerobic and anaerobic exercise effects in the same individual.
In this study, the aerobic work level (60 per
cent) resulted in decreased IOT, but this was not
related to changes in lactate and pH. This finding
has not been previously reported.
A slight additional drop of intraocular tension
was noted following cessation of exercise at all
intensities, and this was associated with a further
increase in blood lactate following cessation of
maximum exercise. The further drop of IOT following cessation of exercise has been noted by
Investigative Ophthalmology
Octoter 1975
others.:i This further drop following cessation of
exercise may be related to the osmotic effect of
the further increase in lactate which is known to
occur following cessation of exercise.8 This change
in IOT could also be due to the drop noted to occur after repeated IOT measurements with a
Schi0tz tonometer.11
The drop of IOT with exercise seemed to be
proportional to the work loads, although not
statistically significant. This observation might be
due to a higher pre-exercise IOT noted prior to
the maximum test. It has been shown that those
individuals with a high baseline IOT tend to
have a greater magnitude of drop of intraocular
tension.1 Intraocular tension approached pre-exercise levels more slowly with greater work loads
and appears to be related with recovery lactate
and pH changes at anaerobic levels (Tables II
and III). This slow recovery may be related to
the osmotic effect of increased blood lactate.
Although the above changes in IOT appear to
be directly related to the intensity of exercise, the
lowest IOT reached at all intensities varied by
only 1.5 mm. Hg. This rather uniform level of
IOT reached with different exercise loads seems
to indicate that the factors responsible for decreasing IOT with exercise effects mechanisms
which have a specific limit to which they can
lower IOT. Lack of a statistically significant difference in the decrease in IOT with various exercise levels, particularly in regard to lack of correlation between decrease in IOT and blood pH
and lactate at the aerobic level, may indicate that
unknown factors at present are responsible for
the decrease in IOT during purely aerobic exercise, and that anaerobic parameters (increased
lactate and decreased pH) may be of a lesser importance in the slight further decrease in IOT
noted with increasing exercise loads. Parameters
other than blood pH and lactate which may effect changes in IOT with exercise are presently
being investigated. A preliminary study seems to
indicate that the arterial blood P c0 ., is an important parameter in regard to rapid changes of
IOT.10
The authors would like to thank Dr. Ernst
Jokl for stimulating our interest in the area of
exercise physiology and its effects upon the eye.
From the Departments of Ophthalmology and
Physical Education, University of Kentucky, Lexington, Ky. Submitted for publication May 1,
1975.
Key words: intraocular tension, blood pH, blood
lactate, aerobic exercise, anaerobic exercise.
REFERENCES
1. Meyers, K. J.: The effect of aerobic exercise
on intraocular pressure, INVEST. OPHTHALMOL.
13: 74, 1974.
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Reports 785
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2. Marcus, D. F., Krupin, T., Podos, S. M., et
al.: The effect of exercise on intraocular pressure. I. Human beings, INVEST. OPHTHALMOL.
9: 749, 1970.
3. Kypke, W., Holge, J., and Scriba, B.:
Augeninnendruck wahrend und nach kroperlicher Belastung. Eine systematische Untersuchung und reproduzierbaren Arbeitsbedingungen. I. Kreislauf parameter, Albrecht von
Craefes Arch. Klin. Exp. Ophthalmol. 186:
91, 1973.
4. Leighton, D. A., and Phillips, C. I.: Effect
of moderate exercise on the ocular tension,
Br. J. Ophthalmol. 54: 599, 1970.
5. Scherrer, M.: Acid-base imbalance and gas
exchange during heavy work, in: Biochemistry of Exercise, Poortmans, J. R., editor.
Basel, 1969, S. Karger.
6. Williams, C. C , Wyndham, C. H., Kole,
R., et al.: Effect of training on maximum
oxygen-intake and on anaerobic metabolism
in man, Int. Z. Augenheilk. Physiol. 24: 18,
1967.
7. Marcus, D. F., Krupin, T., Podos, S. M.,
et al.: The effect of exercise on intraocular
pressure. II. Rabbits, INVEST. OPHTHALMOL.
9: 753, 1970.
8. Astrand, P., and Rodahl, L.: Textbook of
Work Physiology. New York: 1970, McGrawHill Book Company.
9. Stocker, F. W.: On changes in intraocular
tension with application of tonometer, Am.
J. Ophthalmol., 45: 192, 1958.
10. Teraslinna, P., and Kielar, R. A.: The influence of blood P(x>2 on intraocular tension
at rest and during exercise, an investigation
in progress.
Binding of retinol to isolated retinal pigment epithelium in the presence and
absence of retinol-binding protein.
GIOVANNI MARAINI AND FLAVIO GOZZOLI.
Isolated human and bovine pigment epithelium
actively binds H-^-retinol when vitamin A alcohol
is present in the incubation medium bound to
human retinol-binding protein. Pigment epithelium
is unable to bind retinol present in the incubation solution as the free form, i.e., not bound to
its physiologic carrier protein. It is suggested
that an interaction between retinol-binding protein and the membranes of pigment epithelial
cells is essential for the active transport of retinol
into pigment epithelium.
Although in recent years the molecular aspects
of retinol transport in blood have been elucidated,1- - nothing is known about the mechanism
by which vitamin A alcohol is transferred from
its carrier plasma protein to the target cell. This
is of particular interest for the eye where the
aldehyde of vitamin A represents the chromophore
of the visual pigment molecules in photoreceptor
cells. Available experimental evidence suggests
that the retinal pigment epithelium (PE) is involved in the uptake of retinol from the choriocapillaris extravascular space and possibly in its
transfer to the photoreceptors.:f
Retinol is transported in plasma bound to a
specific carrier protein, the retinol-binding protein (RBP), which has a molecular weight of
21,000 daltons. Under physiologic conditions one
molecule of RBP binds one molecule of retinol.
In the plasma RBP circulates bound to a thyroxine-binding prealbumin (molecular weight
64,000 daltons); a retinol-protein-protein complex
of 85,000 daltons thereby results. The binding
of RBP to prealbumin is noncovaJent, probably
involves one of the tryptophan residues of RBP,1
and may be influenced by changes in the functional groups of the retinyl moietyr> as well as
by reductive alkylation of disulfide bonds or
iodination of the two proteins.0 The complex between RBP and prealbumin is dependent on the
ionic strength of the medium and the proteins
dissociate at low salt concentration.7
In the present paper we give some experimental evidence indicating that the presence of
RBP is necessary for the binding of retinol to
isolated PE.
The experiments have been carried out in an
in vitro system utilizing short-term incubations of
human or bovine PE prepared from dark-adapted
eyes by a modification of the technique described by Glocklin and Potts.s Normal human
eyes have been obtained within three hours after
death. After removal of the anterior half of
the globe, the vitreous body was discarded and
the retina carefully detached. After rinsing the
inner surface of the eye cup with 2 ml. of cold
Krebs-Ringer bicarbonate buffer to remove outer
segment fragments, the PE was suspended in a
second volume of buffer by very gentle brushing
with a small soft brush. The PE suspension was
transferred to a centrifuge tube and centrifuged
for 2 minutes at 300 r.p.m. at 4° C. The supernatant was discarded and the cells washed two
more times with 5 ml. of cold buffer as previously
described. Examination of PE preparations by
light and electron microscopy demonstrated that
the cells are very well preserved and without appreciable contamination by rod outer segments
or choroidal remnants.
The metabolic integrity of isolated bovine PE
was checked by evaluating the incorporation of
a radioactive aminoacid into the cell proteins during short-term incubations. After isolation PE
cells were resuspended in Krebs-Ringer bicarbonate buffer containing L-leucine-C14 at a final
concentration of 0.6 nmoles per milliliter and
incubated in water bath at 37° C. for two hours
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