WHAT SUITS BEST FOR ORGAN WEIGHT ANALYSIS: REVIEW OF RELATIONSHIP BETWEEN ORGAN WEIGHT AND BODY / BRAIN WEIGHT FOR RODENT TOXICITY STUDIES

Organ weight analysis is an important endpoint for identification of potentially harmful effects of test compounds in toxicology studies. Organ weight differences are often accompanied by differences in body weights between treatment groups which make the organ weight interpretation more difficult. We have evaluated the relationship between organ weight and body/brain weight based on statistical analysis to determine which endpoint (absolute organ weight, organ-to-body weight ratio, or organ-to-brain weight ratio) is likely to accurately detect target organ toxicity by using data from control rats that were part of 43 toxicity studies conducted under similar conditions. All the organs weight data of both sexes were subjected to the linear regression; correlation was established with body weight and brain weight. Present data set revealed that there was a strong correlation between liver, kidneys and heart weights with body weights. Organs like spleen and adrenal weight also showed correlation with body weight. Other commonly weighed organs in toxicity studies viz. thymus, pituitary and thyroid- parathyroid did not show consistent pattern of relationship with body weights in either sex. If correlation is analyzed with brain weights; organs other than liver, kidneys and heart weights showed no/poor correlation.  In conclusion, analysis of organ weight to body weight ratio is optimum for most of the organs for prediction of toxicity. For organs like ovaries, thyroid- parathyroid, thymus and pituitary gland, either absolute weight or other alternative statistical method should be considered for evaluation of toxic effects.