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Effect of state of administered cholesterol in experimental atherosclerosis
ARCHIVES
OF
BIOCHEMISTRY
AND
BIOPHYSiCS
69,
526-540 (19%)
LETTERS TO THE EDITORS Effect of State of Administered
Cholesterol in Experimental
Atherosclerosis
Recently attention has been focused on the role of cholesterol vehicle in cholesterol-induced atherosclerosis. It has been shown that this sterol is less atherogenie when fed dissolved in fats of high rather than low iodine number (1) and is also less atherogenic in refined than in crude cottonseed oil (2). Feeding of cholesterol in the absence of fat caused the most severe atheromata in the experiment cited (1) and has previously been shown to cause atherosclerosis (3, 4). Indeed, cholesterol has been reported to cause very severe atheromata when administered in the absence of any other food (5). In an attempt to assess the importance of the state of dispersion of administered cholesterol, we have fed 5 groups of rabbits the following diets: regular chow plus 2% cholesterol (applied in a volatile solvent), regular chow plus 2% cholesterol suspended in 6% corn oil, regular chow plus 2% cholesterol dissolved in 6% corn oil, 2% cholesterol-containing pellets (4% ether-alcohol extractable material), and 2% cholesterol-containing pellets mixed with 6% hot corn oil. After 8 weeks on the diet of choice the animals were sacrificed, and the thoracic aorta and the aorta arch graded visually for plaques on a 04 scale. The sera were assayed for total cholesterol by the method of Trinder (6). Results are tabulated below:
-
No. of animals
Diet
/
Average atheromata Arch
Thoracic
10
2.70
2.10
9
2.56
1.72
Cholesterol pellets
10
2.35
1.45
Cholesterol-oil
10
2.40
1.00
8
2.06
1.38
Cholesterol Cholesterol-oil
Pellets-oil
suspension
solution
I
Serum ch3lesterol mg. % ohw)
1147 (333-2138) 1571 (364-2895) 1439 (720-2265) 1335 (690-2280) 2567 (4553435)
The possibility occurs that unsaturated fat may make more cholesterol available to the general metabolism, thus raising serum cholesterol values without increasing atheromata. Recent work has shown that rats fed cholesterol plus unsaturated fat show greater serum cholesterol levels than those fed cholesterol 526
LETTERS
TO THE
527
EDITORS
plus saturated fat (7), and the drop in rat serum cholesterol in an unsaturated fatty acid-freediet has beenreported (8). Our initial data suggest thattheform in which cholesterol is made available to the body may also be important. REFERENCES 1. KRITCHEVSHY, D., MOYER, A. W., TESAR, W. C., LOCAN, J. B., BROWN, R. A., DAVIES, M. C., AND Cox, H. R., Am. J. Physiol. 178, 30 (1964). 2. OPDYKE, D. F., AND OTT, W. H., Proc. Sot. Ezptl. Biol. Med. 86, 414 (1964). 3. TURNER, K. B., AND BIDWELL, E. H., J. Ezptl. Med. 66,116 (1933). 4. WEINHOUSE, S., AND HIRSCH, E. F., Arch. Pathol. 39, 856 (1949). 5. GREENBLAXV, I. J., GOLUB, M., ROSRIN, B., AND AMATO, J., Abstracts of Papers,
122nd Meeting of the American Chemical Society, 1962, p. 48C. 6. TRINDER, P., Analyst 77, 321 (1962). 7. SWELL, L., FLICK, D. F., FIELD, H., AND TREADWELL,
C. R., Am. J. Physiol. 189, 124 (1955). 8. ALFIN-SLATER, R. B., AFTERGOOD, L., WELLS, A. F., AND DEUEL, H. J., Arch. Biochem. and Biophys. 62, 180 (1954). Viral
and RickettsiaZ
Section,
Research Division, American Cyanamid Company, Pearl Rioer, New York Received October SO, 1966
On the Role of Manganese in the Oxygen-Evolving
DAVID KRITCHEVSKY ARDEN W. MOYER JOHN B. LOGAN R. F. J. MCCANDLESS
System of Photosynthesis
Among the many mineral deficiencies that inhibit photosynthesis, the case of manganese is unique insofar as manganese exclusively affects photosynthesis and does not, influence chlorophyll formation and respiration (1). Furthermore, the inhibition of photosynthesis by manganese deficiency can be observed at both high and low light intensities (l-3). In this respect it bears a striking similarity to the effect of hydroxylamine (4), known to be an inhibitor of oxygen evolution in photosynthesis (5, 6). This observation led Pirson to the assumption that manganese might be involved in the oxygen-evolving system of photosynthesis (1) (cf. ref. 7). This hypothesis can be tested experimentally in the following way. Photoreduction in algae adapted to hydrogen is a special type of photosynthesis, where only the oxygen-evolving system is inactive and replaced by a reaction of the photosynthetic oxygen precursors with molecular hydrogen activated by hydrogenase (8). Therefore a factor inhibiting only oxygen evolution in photosynthesis should not inhibit photoreduction at all and, in addition, should stabilize this process against the reversion to normal photosynthesis with evolution of oxygen, which normally occurs at higher light intensities. This was shown to be true in the case of poisoning with hydroxylamine, o-phenanthroline, and phthiocol (5, 6, 8). The green alga, Ankistrodesmus braunii, can easily be adapted to hydrogen metabolism within a few hours in the dark under an atmosphere of Hc + 470 CO%. If photosynthesis and photoreduction at various light intensities are studied in this organism, grown with and without manganese, one obtains the results shown
OF
BIOCHEMISTRY
AND
BIOPHYSiCS
69,
526-540 (19%)
LETTERS TO THE EDITORS Effect of State of Administered
Cholesterol in Experimental
Atherosclerosis
Recently attention has been focused on the role of cholesterol vehicle in cholesterol-induced atherosclerosis. It has been shown that this sterol is less atherogenie when fed dissolved in fats of high rather than low iodine number (1) and is also less atherogenic in refined than in crude cottonseed oil (2). Feeding of cholesterol in the absence of fat caused the most severe atheromata in the experiment cited (1) and has previously been shown to cause atherosclerosis (3, 4). Indeed, cholesterol has been reported to cause very severe atheromata when administered in the absence of any other food (5). In an attempt to assess the importance of the state of dispersion of administered cholesterol, we have fed 5 groups of rabbits the following diets: regular chow plus 2% cholesterol (applied in a volatile solvent), regular chow plus 2% cholesterol suspended in 6% corn oil, regular chow plus 2% cholesterol dissolved in 6% corn oil, 2% cholesterol-containing pellets (4% ether-alcohol extractable material), and 2% cholesterol-containing pellets mixed with 6% hot corn oil. After 8 weeks on the diet of choice the animals were sacrificed, and the thoracic aorta and the aorta arch graded visually for plaques on a 04 scale. The sera were assayed for total cholesterol by the method of Trinder (6). Results are tabulated below:
-
No. of animals
Diet
/
Average atheromata Arch
Thoracic
10
2.70
2.10
9
2.56
1.72
Cholesterol pellets
10
2.35
1.45
Cholesterol-oil
10
2.40
1.00
8
2.06
1.38
Cholesterol Cholesterol-oil
Pellets-oil
suspension
solution
I
Serum ch3lesterol mg. % ohw)
1147 (333-2138) 1571 (364-2895) 1439 (720-2265) 1335 (690-2280) 2567 (4553435)
The possibility occurs that unsaturated fat may make more cholesterol available to the general metabolism, thus raising serum cholesterol values without increasing atheromata. Recent work has shown that rats fed cholesterol plus unsaturated fat show greater serum cholesterol levels than those fed cholesterol 526
LETTERS
TO THE
527
EDITORS
plus saturated fat (7), and the drop in rat serum cholesterol in an unsaturated fatty acid-freediet has beenreported (8). Our initial data suggest thattheform in which cholesterol is made available to the body may also be important. REFERENCES 1. KRITCHEVSHY, D., MOYER, A. W., TESAR, W. C., LOCAN, J. B., BROWN, R. A., DAVIES, M. C., AND Cox, H. R., Am. J. Physiol. 178, 30 (1964). 2. OPDYKE, D. F., AND OTT, W. H., Proc. Sot. Ezptl. Biol. Med. 86, 414 (1964). 3. TURNER, K. B., AND BIDWELL, E. H., J. Ezptl. Med. 66,116 (1933). 4. WEINHOUSE, S., AND HIRSCH, E. F., Arch. Pathol. 39, 856 (1949). 5. GREENBLAXV, I. J., GOLUB, M., ROSRIN, B., AND AMATO, J., Abstracts of Papers,
122nd Meeting of the American Chemical Society, 1962, p. 48C. 6. TRINDER, P., Analyst 77, 321 (1962). 7. SWELL, L., FLICK, D. F., FIELD, H., AND TREADWELL,
C. R., Am. J. Physiol. 189, 124 (1955). 8. ALFIN-SLATER, R. B., AFTERGOOD, L., WELLS, A. F., AND DEUEL, H. J., Arch. Biochem. and Biophys. 62, 180 (1954). Viral
and RickettsiaZ
Section,
Research Division, American Cyanamid Company, Pearl Rioer, New York Received October SO, 1966
On the Role of Manganese in the Oxygen-Evolving
DAVID KRITCHEVSKY ARDEN W. MOYER JOHN B. LOGAN R. F. J. MCCANDLESS
System of Photosynthesis
Among the many mineral deficiencies that inhibit photosynthesis, the case of manganese is unique insofar as manganese exclusively affects photosynthesis and does not, influence chlorophyll formation and respiration (1). Furthermore, the inhibition of photosynthesis by manganese deficiency can be observed at both high and low light intensities (l-3). In this respect it bears a striking similarity to the effect of hydroxylamine (4), known to be an inhibitor of oxygen evolution in photosynthesis (5, 6). This observation led Pirson to the assumption that manganese might be involved in the oxygen-evolving system of photosynthesis (1) (cf. ref. 7). This hypothesis can be tested experimentally in the following way. Photoreduction in algae adapted to hydrogen is a special type of photosynthesis, where only the oxygen-evolving system is inactive and replaced by a reaction of the photosynthetic oxygen precursors with molecular hydrogen activated by hydrogenase (8). Therefore a factor inhibiting only oxygen evolution in photosynthesis should not inhibit photoreduction at all and, in addition, should stabilize this process against the reversion to normal photosynthesis with evolution of oxygen, which normally occurs at higher light intensities. This was shown to be true in the case of poisoning with hydroxylamine, o-phenanthroline, and phthiocol (5, 6, 8). The green alga, Ankistrodesmus braunii, can easily be adapted to hydrogen metabolism within a few hours in the dark under an atmosphere of Hc + 470 CO%. If photosynthesis and photoreduction at various light intensities are studied in this organism, grown with and without manganese, one obtains the results shown