Species and Strain Differences in Urinary Protein Excretion

Abstract

The physiological excretion of urinary protein is subject to great variation influenced not only by environmental and hormonal factors but also by genetics. The present study demonstrates that there is not only variation in respect to the excretion of plasma proteins but also of other types of proteins which are specific urinary proteins. There is a close relation between body weight and total protein excretion. However, male rats and mice do not fit the allometric line calculated for the other species studied. This is of special importance since these two species are often used in kidney research. The reason for this divergence in total protein is the excretion of sex-dependent low molecular weight proteins. The excretion of albumin, which is a marker of glomerular permeability and tubular reabsorption as well, shows a marked genetic variation between different rat strains. The data presented in this study demonstrate the general admissibility of transferring data from one species to the other but also the limitations in respect especially to the sex-dependent proteins which are excreted by some species.

Strain Differences in Morphometrical Characteristics of Rat Kidneys

“…Hackbarth et al [7] analyzed the GFR and RPF of seven strains of female rats, including the sublines of Wistar and SD rats, and they demonstrated the strain differences of these two parameters. Alt et al [1] analyzed the urinary protein of 13 strains of rats, including Wistar and SD rats, and they demonstrated that the rate of low molecular weight protein excretion was different depending on the strain and sex. However, relationships between the findings of these previous reports and those in the present study were not observed.…”

“…Rats are frequently used in animal experiments, and there have been many reports regarding the sex differences in the morphology and function of the rat kidneys; e.g., the segmentation of nephrons [13], the thickness of each of the renal zones [16], the ultrastructural features of the proximal tubular epithelium [21,27], the concentration and constituents of the urine [1,11,16], and the structural and functional alterations with aging [3,6,18,22]. The effects of castration and sex hormone-treatment in the rat kidneys have also been investigated, and the effects on the size of the glomeruli and proximal tubules [14], ultrastructural features of the proximal tubular epithelium [21,27], concentration and constituents of urine [11,16], and the severity of glomerular damage with aging or after uninephrectomy [3,5,15,19,20], have been reported.…”

“…The effects of castration and sex hormone-treatment in the rat kidneys have also been investigated, and the effects on the size of the glomeruli and proximal tubules [14], ultrastructural features of the proximal tubular epithelium [21,27], concentration and constituents of urine [11,16], and the severity of glomerular damage with aging or after uninephrectomy [3,5,15,19,20], have been reported. Regarding the strain differences, several reports demonstrated the strain differences in the urinary constituents [1], glomerular filtration rate (GFR) [7], renal plasma flow (RPF) [7], pathological changes with aging [6,18,22], and the sensitivity to nephrotoxicity due to chemical drugs [4,17] and high-protein food [12].…”

Rodent Renal Structure Differs among Species

“…A cytochemical study previously indicated active absorption by CPL in male mice [11]. In addition, physiological hyperfiltration was observed in male mice and rats, and GFR and urinary protein excretion volume were significantly higher in males [2,17,19]. From these findings, we surmised that CPL of male mice, rats, and gerbils contributes to the reabsorption of excessive filtrated urinary proteins.…”

NC100668, a New Tracer Tested for Imaging of Venous Thromboembolism: Pharmacokinetics and Metabolism in Humans

“…The difficulty in quantifying these metabolites in rat urine is probably a result of the much higher (and varying) concentration of both high-and low-molecular-weight substances in rat urine (Alt et al, 1985) and illustrates the differences in rat and human kidneys in handling proteins and peptides.…”