Effect of casein, casein phosphopeptides and calcium intake on ileal 45Ca disappearance and temporal systolic blood pressure in spontaneously hypertensive rats

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Abstract
Paracellular 45Ca absorption and temporal systolic blood pressure (SBP) measurements were recorded in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) ratsfed on casein (C) and soya-bean-protein isolate (S) diets, containing 20 (H), 5 (M) and 0.5(L)g Ca/kg. Similar measurements were also taken in SHR rats only fed on C-M and S-M dietssupplemented with 30 g caseinophosphopeptides (CPP)/kg. Absorption of 45Ca fromthe ileal loop was equivalent in both SHR and WKY animals and largely affected by the level ofdietary Ca. In addition, animals fed on C diets exhibited significantly (P < 0.05) greater ileal absorption of 45Ca compared with S-fed animals. This result was attributed to the presence of CPP and a greater (P < 0.05) proportion of soluble 45Ca inthe contents of the ileum. Animals fed on S diets supplemented with CPP confirmed this finding.The SBP of SHR rats was higher (P < 0.01) than WKY controls after 9–10 weeks of age. The temporal pattern of observed hypertension was independent of dietary influence in the SHR. The severity of hypertension in SHR rats was affected only by dietary Ca deficiency, and not byCa supplementation or CPP enhancement of Ca bioavailability. These findings suggest that trypticdigestion products of casein in milk can enhance Ca bioavailability by increasing Ca solubility; however, this action had no effect in reducing hypertension in SHR.