248
J O H N P A U L
Occasionally, other unusual requirements have been reported. Thus
Neuman and McCoy (1958) found that growth of isolated Walker
carcinosarcoma 265 cells was stimulated by the addition of keto acids,
such as pyruvate, oxaloacetate and oxoglutarate, to the medium. This
may be attributable to leakiness of the cells to these substances as
reported by Danes and Paul (1961b).
The rate of utilization of carbohydrate varies widely, depending not
only on the cells studied but also, as will be shown, on the conditions of
culture. When conditions are otherwise kept constant, however, fairly
characteristic rates are found, varying in one study from 0-13 mg to
1-51 mg glucose per million cells per day (Bryant, Schilling and Earle,
1958) for a variety of cell-types. Different hexoses are utilized at
different rates by the same cells (Bailey et al., 1959; Eagle et al., 1958)
and this is probably related to the activity of the appropriate kinases
(Eagle etal, 1958).
2. General Pathways of Carbohydrate Catabolism
While it is often stated (with good reason as will be shown) that the
metabolism of cultured cells is predominantly glycolytic (AbdelTawab, Broda and Kellner, 1959; Agol, Gershanovitch and Etingof,
1959; Graff and McCarty, 1958; Green, Henle and Deinhardt, 1958;
Hori, Takaoka and Katsuta, 1958; S. Kuwabara, 1959) and all the
enzymes of the Embden-Meyerhof pathway have been demonstrated
by W u (1959) and others (Etingof and Gabrielyan, 1959; Matzelt and
Homann, 1958) there is ample evidence that other pathways of carbohydrate catabolism are fully present and quite active. Most cells have
a steady respiratory rate of between 10~
5 and 10~
6 /xl 0 2 per hour per
cell (Danes, 1955a, b ; Danes and Leinfelder, 1951; Danes, Christiansen
and Leinfelder, 1954; Danes and Paul, 1961a, b ; Laser, 1933; Phillips
and Feldhaus, 1956; Phillips and Terryberry, 1958; Warburg and
Kubowitz, 1927) which itself provides adequate evidence for the
existence of oxidative pathways in cultured cells. Ultimate evidence,
however, is supplied by the demonstration of the existence of the
enzymes of the citric acid cycle in HeLa cells by Barban and Schulze
(1956). The evidence for the pentose-phosphate shunt is not quite so
conclusive but Crockett and Leslie (Crockett, 1961) have shown with
the H L M cell that in appropriate conditions the
1 4
C 0 2 yield from
1 4
C-1-glucose is greater than the yield from
1 4
C-U-glucose of the same
specific activity. Kinoshita and Wachtl (1958) have made similar
observations in short-term cultures of lens.
The functioning of other connecting pathways of carbohydrate
metabolism is implied by the ability to utilize sugars such as galactose,
ribose and xylose.
J O H N P A U L
Occasionally, other unusual requirements have been reported. Thus
Neuman and McCoy (1958) found that growth of isolated Walker
carcinosarcoma 265 cells was stimulated by the addition of keto acids,
such as pyruvate, oxaloacetate and oxoglutarate, to the medium. This
may be attributable to leakiness of the cells to these substances as
reported by Danes and Paul (1961b).
The rate of utilization of carbohydrate varies widely, depending not
only on the cells studied but also, as will be shown, on the conditions of
culture. When conditions are otherwise kept constant, however, fairly
characteristic rates are found, varying in one study from 0-13 mg to
1-51 mg glucose per million cells per day (Bryant, Schilling and Earle,
1958) for a variety of cell-types. Different hexoses are utilized at
different rates by the same cells (Bailey et al., 1959; Eagle et al., 1958)
and this is probably related to the activity of the appropriate kinases
(Eagle etal, 1958).
2. General Pathways of Carbohydrate Catabolism
While it is often stated (with good reason as will be shown) that the
metabolism of cultured cells is predominantly glycolytic (AbdelTawab, Broda and Kellner, 1959; Agol, Gershanovitch and Etingof,
1959; Graff and McCarty, 1958; Green, Henle and Deinhardt, 1958;
Hori, Takaoka and Katsuta, 1958; S. Kuwabara, 1959) and all the
enzymes of the Embden-Meyerhof pathway have been demonstrated
by W u (1959) and others (Etingof and Gabrielyan, 1959; Matzelt and
Homann, 1958) there is ample evidence that other pathways of carbohydrate catabolism are fully present and quite active. Most cells have
a steady respiratory rate of between 10~
5 and 10~
6 /xl 0 2 per hour per
cell (Danes, 1955a, b ; Danes and Leinfelder, 1951; Danes, Christiansen
and Leinfelder, 1954; Danes and Paul, 1961a, b ; Laser, 1933; Phillips
and Feldhaus, 1956; Phillips and Terryberry, 1958; Warburg and
Kubowitz, 1927) which itself provides adequate evidence for the
existence of oxidative pathways in cultured cells. Ultimate evidence,
however, is supplied by the demonstration of the existence of the
enzymes of the citric acid cycle in HeLa cells by Barban and Schulze
(1956). The evidence for the pentose-phosphate shunt is not quite so
conclusive but Crockett and Leslie (Crockett, 1961) have shown with
the H L M cell that in appropriate conditions the
1 4
C 0 2 yield from
1 4
C-1-glucose is greater than the yield from
1 4
C-U-glucose of the same
specific activity. Kinoshita and Wachtl (1958) have made similar
observations in short-term cultures of lens.
The functioning of other connecting pathways of carbohydrate
metabolism is implied by the ability to utilize sugars such as galactose,
ribose and xylose.