17.
A C T I O N S O F
V I T A M I N S A
A N D
C
685
The concept of a vitamin is still inseparable from that of a growth
factor in the mind of many biologists, although the action of some
vitamins has little to do with cell enlargement or cell division. Since
vitamin C is required for normal growth of young guinea-pigs it has
been assumed, almost inevitably, that it plays an important role in
growth regulation. If we include the synthesis of collagen and ground
substances in our concept of growth, this may well be so, but if we think
in terms of cell size and cell division, the connection seems, on present
evidence, far-fetched.
Apart from the indirect evidence afforded by the high concentration of ASA in rapidly growing tissues and organs of embryos
(Rinaldini, 1960), plants (Reid, 1938; Chayen, 1953), animals (Bessey
and King, 1933) and man (Yarkosky et aL, 1934), and the higher
utilization by young than by old animals (Reid, 1948, 1950), there is
little evidence either in vivo or in cultures for a direct effect of ASA on any
o f the biological phenomena that we are used to encompass in the
complex process of growth. A rough correlation was observed in some
embryonic organs of the chick between A S A concentration and mitotic
rate (Rinaldini, 1960) but this may be fortuitous.
In plant seedlings, however, Reid (1941) found an increase in ASA
per cell of more than tenfold from the early cell-division stage to the
maturation stage, and no further increase after maturation. The
increase in cell surface was found to parallel that in vitamin content.
Newcomb (1951) reported that cell enlargement induced by auxin in
cultures of tobacco pith cells was accompanied by a high increase in
ascorbic-acid-oxidase activity. Conversely, treatment with ASA
inhibits auxin-induced growth, according to Tonzig and Marre (1961).
Chayen's report (1953) of cyclic fluctuations in the reduced form of the
vitamin during the mitotic cycle of Viciafaba affords the only indication
known to me of a direct involvement of vitamin C in cell division. It
would be of great interest to investigate these fluctuations in relation to
the well-established sulphydryl-disulphide mitotic cycle studied by
Rapkine and by Mazia (see Mazia, 1954; Swann, 1957) and to the
respiratory systems involving D H A and GSH (Ames and Elvehjem,
1946; Mapson and Goddard, 1951; Mapson, 1954, 1961; Staudinger,
Kirsch and Loenhauser, 1961).
The evidence in favour of a relation between ASA and growth must
be weighed against the fact that some non-growing tissues in plants and
animals, such as citrus fruits, the lens and the adrenals, have a high
ASA content. The question of the possible role of vitamin C in mitosis
should be explored with more refined experiments on the effect of
reduced and oxidized ascorbic at precise stages of the division cycle in
synchronized cultures.
A C T I O N S O F
V I T A M I N S A
A N D
C
685
The concept of a vitamin is still inseparable from that of a growth
factor in the mind of many biologists, although the action of some
vitamins has little to do with cell enlargement or cell division. Since
vitamin C is required for normal growth of young guinea-pigs it has
been assumed, almost inevitably, that it plays an important role in
growth regulation. If we include the synthesis of collagen and ground
substances in our concept of growth, this may well be so, but if we think
in terms of cell size and cell division, the connection seems, on present
evidence, far-fetched.
Apart from the indirect evidence afforded by the high concentration of ASA in rapidly growing tissues and organs of embryos
(Rinaldini, 1960), plants (Reid, 1938; Chayen, 1953), animals (Bessey
and King, 1933) and man (Yarkosky et aL, 1934), and the higher
utilization by young than by old animals (Reid, 1948, 1950), there is
little evidence either in vivo or in cultures for a direct effect of ASA on any
o f the biological phenomena that we are used to encompass in the
complex process of growth. A rough correlation was observed in some
embryonic organs of the chick between A S A concentration and mitotic
rate (Rinaldini, 1960) but this may be fortuitous.
In plant seedlings, however, Reid (1941) found an increase in ASA
per cell of more than tenfold from the early cell-division stage to the
maturation stage, and no further increase after maturation. The
increase in cell surface was found to parallel that in vitamin content.
Newcomb (1951) reported that cell enlargement induced by auxin in
cultures of tobacco pith cells was accompanied by a high increase in
ascorbic-acid-oxidase activity. Conversely, treatment with ASA
inhibits auxin-induced growth, according to Tonzig and Marre (1961).
Chayen's report (1953) of cyclic fluctuations in the reduced form of the
vitamin during the mitotic cycle of Viciafaba affords the only indication
known to me of a direct involvement of vitamin C in cell division. It
would be of great interest to investigate these fluctuations in relation to
the well-established sulphydryl-disulphide mitotic cycle studied by
Rapkine and by Mazia (see Mazia, 1954; Swann, 1957) and to the
respiratory systems involving D H A and GSH (Ames and Elvehjem,
1946; Mapson and Goddard, 1951; Mapson, 1954, 1961; Staudinger,
Kirsch and Loenhauser, 1961).
The evidence in favour of a relation between ASA and growth must
be weighed against the fact that some non-growing tissues in plants and
animals, such as citrus fruits, the lens and the adrenals, have a high
ASA content. The question of the possible role of vitamin C in mitosis
should be explored with more refined experiments on the effect of
reduced and oxidized ascorbic at precise stages of the division cycle in
synchronized cultures.