METHODS OF CLINICAL EXAMINATION OF RENAL- FUNCTION IN HORSES AND REFERENCE VALUES OF HEALTHY ANIMALS

Investigations of renal function have been done on the basis of renal clearance (Clr) and excretion (E) of endogeneous creatinine in healthy horses of different body weight (23 female, 7 male). Creatinine was m easured by enzymatic PAP-method. Creatinin-E of female horses was poor positively correlated with body weight. The creatinin-Clr was highly correlated with the inulin-Clr (r = 0,896, p < 0,001). The excretion o f creatinine was 35 % higher than the filtration of creatinine, determ ined by inulin-Clr. That demonstrate a tubular netto secretion of 26 % of the total creatinin excretion. However the creatinin-Clr may be co nsidered representative enough for the glomerular filtration rate (GFR ). Water, sodium, glucose and L-lactate were absorbed in the renal tub ules nearly completely, with a fractional excretion (FE) lower 2 %. So they are suitable as endogeneous markers for insufficient tubular abs orption. Other electrolytes were absorbed incompletely depending on th e supply of these substances (calcium-FE and magnesium-FE: 1-50 %, kal ium-FE: 10-120 %, phosphate-FE: 0-5 %). An extremely variable part of the filtered urea was reabsorbed in the tubuli (urea-FE 8-85 %). For t hat reason urea is not appropriate for the diagnostic of disturbances of renal functions. A method for clinical determination bf renal funct ion by measurement of concentrations of metabolites and electrolytes i n blood plasma and spontaneous urine is described and evaluated. The m ethod is based on the supposed constant excretion of the creatinin (0, 17 mu mol/min/kg) and allows especially the examination of male and s ick animals without quantitative sampling of urin. Reference-values fo r the renal excretion of electrolytes and metabolites of healthy horse s are given.