Feeding soy protein isolate and oils rich in omega-3 polyunsaturated fatty acids affected mineral balance, but not bone in a rat model of autosomal recessive polycystic kidney disease

Table 3 Calcium and phosphorus balance in growing female PCK rats fed different diets

Measurement*	Casein + CO	Casein + SO	SPI + SO	SPI + SB	P -value
Water intake (mL/d)	14.4 ± 9.4	15.2 ± 13.7	16.3 ± 11.5	16.5 ± 12.3	0.79
Urinary Output (mL/d)	2.1 ± 0.2b	2.3 ± 0.2b	3.8 ± 0.3a	3.5 ± 0.3a	0.01
Fecal Output (mg/d)	5.2 ± 0.3	5.0 ± 0.3	5.5 ± 0.3	5.7 ± 0.2	0.21
Calcium
Ca Intake (mg/d)	131.3 ± 2.4b	123.0 ± 2.2b	144.7 ± 2.1a	156.6 ± 2.4a	<0.001
Urinary Ca Excretion (mg/mL)¹	1.9 ± 0.3a	1.6 ± 0.5a	0.5 ± 0.07b	1.3 ± 0.3ab	0.02
Fecal Ca Excretion (mg/d)	29.9 ± 2.3	27.2 ± 2.3	26.0 ± 2.2	29.0 ± 2.7	0.65
Ca Apparent Absorption (%)²	77.2 ± 1.7	77.9 ± 1.9	82.0 ± 1.5	81.5 ± 1.7	0.12
Ca Retention (mg/d)³	75.7 ± 1.7b	76.6 ± 1.8b	81.7 ± 1.5a	80.6 ± 1.7a	0.04
Phosphorus
P Intake (g)	91.8 ± 1.0b	97.0 ± 2.1b	109.8 ± 2.0a	108.6 ± 2.3a	<0.001
Urinary P Excretion (mg/mL)⁴	7.9 ± 1.0a	6.8 ± 1.3a	3.4 ± 0.6b	2.3 ± 0.6b	0.01
Fecal P Excretion (mg/d)	26.1 ± 2.6	28.4 ± 1.3	28.3 ± 2.5	26.3 ± 2.7	0.85
P Apparent Absorption (%)⁵	71.6 ± 2.9	70.7 ± 1.4	74.2 ± 2.3	75.7 ± 2.5	0.42
P Retention (mg/d)⁶	63.0 ± 3.1b	63.7 ± 1.8b	71.1 ± 2.5a	73.6 ± 2.3a	0.04
Serum parathyroid hormone (pg/mL)	36.2 ± 4.1	37.2 ± 4.4	39.9 ± 5.2	43.6 ± 5.9	0.74
Serum Ca (mg/mL)	0.12 ± 0.004	0.12 ± 0.001	0.11 ± 0.004	0.11 ± 0.004	0.17
Serum P (mg/mL)	0.12 ± 0.006	0.13 ± 0.007	0.11 ± 0.006	0.12 ± 0.005	0.32

^*Values are expressed as the mean _± SEM of n = 12 rats/group. Different letters a, b within the same column indicate significant differences at P < 0.05 by one-way ANOVA followed by Tukey’s test. Abbreviations are SO soybean oil, SPI soy protein isolate, SB 1:1 soybean oil:salmon oil blend, Ca calcium; P phosphorus.
¹Urinary calcium excretion was calculated as urinary Ca concentration/urine volume.
²Calcium apparent absorption was calculated as [(Ca intake – fecal Ca excretion)/Ca intake] x 100.
³Calcium retention was determined by calculating [Ca intake – (fecal Ca excretion + urinary Ca excretion)].
⁴Urinary phosphorus excretion was calculated as urinary P concentration/urine volume.
⁵Phosphorus apparent absorption was calculated as [(P intake – fecal P excretion)/P intake] x 100.
⁶Phosphours retention was determined by calculating [P intake – (fecal P excretion + urinary P excretion)].

ISSN: 1471-2369