Comparison of Standard Clinical Pathology Parameter Values in Fasted and Fed Rats and Non-human Primates

Area of Science:

• Veterinary medicine
• Toxicology
• Pharmacology

Background:

• Clinical pathology parameters are crucial in pharmacologic safety assessments.
• The effect of non-fasting on these parameters is not well understood.
• Standardized fasting protocols are often employed, but their necessity requires evaluation.

Purpose of the Study:

• To characterize hematology, coagulation, and clinical chemistry changes in fasted versus fed rats and macaques.
• To assess the impact of non-fasting on standard clinical pathology parameters.
• To inform best practices for animal handling in safety studies.

Main Methods:

• Adult Sprague-Dawley rats and cynomolgus macaques were sampled after free feeding and after an 8-hour fast.
• Hematology, coagulation, and clinical chemistry parameters were analyzed.
• Data from fed and fasted states were compared between species and sexes.

Main Results:

• Fed rats showed minor changes in hematology (reticulocytes, neutrophils in males) and significant shifts in clinical chemistry (e.g., higher liver enzymes, glucose, lipids; lower urea, albumin).
• Fed macaques exhibited minor changes (higher triglycerides, lower phosphorus, total bilirubin).
• Coagulation and hematology in macaques were unaffected by non-fasting; coagulation in rats was also unaffected.

Conclusions:

• Non-fasting has a minimal impact on most standard clinical pathology parameters in rats and macaques.
• Fasting is still recommended when evaluating glucose, lipid metabolism, or endocrine systems.
• These findings support refining animal handling protocols in safety assessments.