356
CHARLES J. KREBS AND JUDITH H. MYERS
In addition, respiratory rates of cultured adrenals are indicators of
adrenal activity and the response of adrenal glands to ACTH is another
measure of the state of the glands.
Andrews (1968) studied adrenal activity in brown lemmings from
Barrow, Alaska. His &st observation was that cultured adrenals
display a circadian fluctuation in secretory activity. Therefore, comparisons among groups of individuals must be made over standard
lengths of time, and during the same time of the day. The whole process
is complicated by the fact that Andrews (1968) stored animals for
varying lengths of time in the laboratory and this changed the timing
of the circadian secretory rhythm of the adrenals. Comparison among
groups in this study is most difficult.
A second complicating factor in the interpretation of Andrew’s
data is that his three measures of adrenal activity are not correlated.
The highest respiratory rates, and secretory rates measured by the
conversion of C1“ acetate into corticosteroids, occurred in a sample
of lemmings collected from a peak population in July and killed for
analysis three weeks later in early August. However, the highest rate of
corticosteroid secretion measured, using fluorometric determination of
ethylacetate extractable steroids, occurred in a sample of lemmings also
collected from a peak density population in July but maintained in the
laboratory until February when they were analyzed. These results
indicate that different biochemical pathways for the production of
corticosteroids are being used under varying conditions. The biological
significance of these results was not interpreted by Andrews (1968).
There are few statistics used in Andrews’ (1968) study and so it
is difficult to make comparisons between samples. However, all of his
lemming samples were collected in July 1965, a year of peak lemming
density a t Barrow, Alaska (Pitelka, 1972). The factor which varied
among samples was the length of time the lemmings were maintained in
the laboratory. Therefore, when Andrews (1968, p. 91) talks about
“glands obtained during summer 1965 and winter 1966, following a
lemming population crisis”, in fact he has collected animals from the
same peak population and merely analyzed the adrenals after varying
lengths of time. It is doubtful whether there is any correspondence
between the physiological state of peak density lemmings maintained
in the laboratory for seven months, and lemmings which remain in the
natural population after the population decline. The only conclusion
that can be drawn is that maintaining lemmings in the laboratory seems
to change the secretion of adrenosteroids, but we have not advanced in
understanding the biology of lemmings.
The respiration rate of adrenals of lemmings collected during the
summer of population increase (1964) and the summer of the peak (1965)
CHARLES J. KREBS AND JUDITH H. MYERS
In addition, respiratory rates of cultured adrenals are indicators of
adrenal activity and the response of adrenal glands to ACTH is another
measure of the state of the glands.
Andrews (1968) studied adrenal activity in brown lemmings from
Barrow, Alaska. His &st observation was that cultured adrenals
display a circadian fluctuation in secretory activity. Therefore, comparisons among groups of individuals must be made over standard
lengths of time, and during the same time of the day. The whole process
is complicated by the fact that Andrews (1968) stored animals for
varying lengths of time in the laboratory and this changed the timing
of the circadian secretory rhythm of the adrenals. Comparison among
groups in this study is most difficult.
A second complicating factor in the interpretation of Andrew’s
data is that his three measures of adrenal activity are not correlated.
The highest respiratory rates, and secretory rates measured by the
conversion of C1“ acetate into corticosteroids, occurred in a sample
of lemmings collected from a peak population in July and killed for
analysis three weeks later in early August. However, the highest rate of
corticosteroid secretion measured, using fluorometric determination of
ethylacetate extractable steroids, occurred in a sample of lemmings also
collected from a peak density population in July but maintained in the
laboratory until February when they were analyzed. These results
indicate that different biochemical pathways for the production of
corticosteroids are being used under varying conditions. The biological
significance of these results was not interpreted by Andrews (1968).
There are few statistics used in Andrews’ (1968) study and so it
is difficult to make comparisons between samples. However, all of his
lemming samples were collected in July 1965, a year of peak lemming
density a t Barrow, Alaska (Pitelka, 1972). The factor which varied
among samples was the length of time the lemmings were maintained in
the laboratory. Therefore, when Andrews (1968, p. 91) talks about
“glands obtained during summer 1965 and winter 1966, following a
lemming population crisis”, in fact he has collected animals from the
same peak population and merely analyzed the adrenals after varying
lengths of time. It is doubtful whether there is any correspondence
between the physiological state of peak density lemmings maintained
in the laboratory for seven months, and lemmings which remain in the
natural population after the population decline. The only conclusion
that can be drawn is that maintaining lemmings in the laboratory seems
to change the secretion of adrenosteroids, but we have not advanced in
understanding the biology of lemmings.
The respiration rate of adrenals of lemmings collected during the
summer of population increase (1964) and the summer of the peak (1965)