1300
TABLE 7.
R. C. STEINKAMP, ef al.
MEANS, STANDARD DEVIATIONS AND RANGES OF POTASSIUM-40 AND RELATED Bopy
COMPOSITION MEASUREMENTS
Males 25-44 years
Females 25-44 years
(n =44)
Mean
kK?" counts /min
148
K Total (g)
136
K-equivalents
3.48
Body wt. (kg)
TAI
K m-equiv/kg body wt. 45
LBW K*° (kg)
51.10
LBM* (kg)
58,42
S.D.
20.6
18.9
0.48
12.7
5.4
7.04
8.41
*From TBW-body density technique.
Sid:
(n = 24)
Range
Mean
105-208
96-191
2.46—4.89
57.21-121,59
32-57
41.69-71.67
99
91
2.33
62.46
38
34.27
40.33-84,.11
41.74
S.D.
12.4
11.4
0.29
14.2
5.6
4,20
7.72
i
Range
84-133
77-122
1.97-3.12
46,93-107.81
27-45
28.9445, 82
33.43-69,42
a
.
Sixty-eight subjects (44 men and 24 women) had K*’ determinations in addition
to TBW-body density determinations (Table 7). The calculated K equivalents
compare favorably with those found by ALLEN et al. [12]. They found an average
of 3.975 K equivalents for 507 men aged 25-45 years and an average of 2.521 K
equivalents for 156 women aged 24-44 years. For similar age groups reported here,
mean K equivalents for men were 3.48+0.48 and for women 2.33+0.29.
The ranges of potassium content for our subjects were 32-57 m-equiv/kg for the
men and 27-45 m-equiv/kg for the women. These are close to the ranges found by
Foreset al. [7] for 42 men aged 11-44 years, 35-58 m-equiv/kg, and for 8 women
aged 7-23 years, 23-52 m-equiv/kg. The small differences may be attributed to
the demonstrated differences of total body potassium with relation to age as shown
by ALLEN ef al. [12] and the small number of women in ForBEs’ group[7].
While Forses et al. [7] have suggested a new approach to body composition
measurements, the method has not been studied sufficiently to define what is actually
measured by whole body counting of K*° in terms of fat, muscle and bone. They
have assumed this measurement to be indicative of all body weight exclusive offat.
However, we suggest that it may account for neither bone nor fat.
This suggestion
is based on the comparison of K** data with TBW-body density data as measured in
the same individuals, and reported here, as well as the following reasons. Potassium
is primarily intracellular with little in bone (exclusive of marrow) and fat.
The
measurement of K*° is calculated on the basis of dilution of K*? after an equilibra-
tion period.
fatde:
Whether K** appears during the equilibration period in the sparse
cellular population of the bone is not known. In addition, chemical analysis of
potassium by ashing procedures is not exactly comparable to the indirect isotopic
method. For this paper, therefore, LBW K*° calculated from the measured total K
and the factor, 68.1 (potassium content in meq/kg from cadaver analysis), is thus
defined as body weight less bone and fat. Mean LBW*“* for the 44 men was 51.10+
7.04 kg and for the 24 women was 34.27'4 4.20 kg (Table 7). Correlation coefficients
for LBM and LBW**° were 0.861 for the men and 0.798 for the women. Correla-
tions of LBW*“° and TBW were slightly higher, 0.880 for the men and 0.813 for
the women.
LBM,as calculated from TBW-body density technique and the body weight, is
essentially equivalent to BEHNKE’s ‘lean-body mass’ [13]. LBM differs from the
dit?
pri.
res
fat