Nephropathy seen in rats after high-dose limonene
does not appear to be possible in humans,
since neither the quantity nor type of protein that binds
d-limonene or d-limonene-1,2-oxide is present. The
protein content of human urine is very different from
rat urine, as humans excrete very little protein if any (1
percent or less of the concentration found in urine of
male rats). There is also no protein in human plasma or
urine identical to α2u-globulin and no α2u-g-like protein
has been detected in human kidney tissue. Although
d-limonene-1,2-oxide binds to α2u-g, no other proteins,
particularly those synthesized by humans, bind
d-limonene-1,2-oxide. Finally, there is no evidence that
any human protein can contribute to a renal syndrome
similar to α2u-globulin nephropathy.