Veterinary Clinical Biochemistry and Laboratory Diagnosis

INTRODUCTION

• Creatine and creatinine are metabolized in the kidneys, muscle, liver and pancreas. Structurally, creatine is a methylguanidinoacetic acid which makes up to 98% of total muscle mass and plays a crucial role in muscle contraction. Creatine is excreted in the form of anhydride, i.e. creatinine. Serum creatine concentration is increased in muscular atrophy and following extremity amputation. Excessive proteinuria results from impaired tubular creatine reabsorption. Determination of creatinuria has a diagnostic value only in case of atrophy and in muscle regeneration in myopathies. Creatine phosphate undergoes spontaneous breakdown in muscle cells to form creatinine.
• The loss of water molecule from creatine results in the formation of creatinine. Creatinine is transferred to the kidneys by blood plasma, wherefrom it is eliminated from the body by glomerular filtration and partial tubular excretion. Serum concentration of creatinine primarily depends on glomerular filtration. Plasma and urine creatinine level is a fairly constant value which is related to total muscle mass. As creatinine is endogenously formed and is not reabsorbed in the tubules, serum creatinine is a reliable indicator of glomerular function.