Comparative expression profiling of insulin-like growth factor binding protein-5 in milk of Bos indicus and Bubalus bubalis during lactation

Insulin-like growth factor binding protein-5 (IGFBP-5) is a key molecule in mammary gland development, which facilitates the removal of mammary epithelial cells (MECs) by apoptosis that takes place during remodeling of the mammary gland during involution. IGFBP-5 binds with IGFs for their bioavailability. IGFBP-5 has been reported to perform pleiotropic roles such as cellular apoptosis, proliferation and differentiation. To understand the role of IGFBP-5 during lactation and clinical mastitis, expression profiling of IGFBP-5 at the protein level was performed in both indigenous cows (Bos indicus) and buffaloes (Bubalus bubalis) belonging to two different breeds – Sahiwal cows and Murrah buffaloes. Reverse-transcriptase PCR (RT-PCR) of IGFBP-5 mRNA confirmed its expression in milk somatic cells and MECs of Sahiwal cows. ELISA was performed for quantitative measurement of IGFBP-5 concentrations in milk during different days (0, 50, 100, 150, 200, 250 and 300) of lactation, during the involution period and in animals exhibiting short lactation and clinical mastitis. The highest concentration of IGFBP-5 in milk was observed during the involution period followed by colostrum, late and early lactation, respectively, in both cattle and buffaloes. No significant difference in the concentration of IGFBP-5 was observed during the first 150 days of lactation between cows and buffaloes. However, higher concentration of IGFBP-5 was observed in cows during late lactation (200 to 300 days) in comparison with buffaloes. To validate the ELISA data, quantitative real-time PCR was performed in MECs of Sahiwal cows. The relative mRNA abundance of IGFBP-5 was found to be significantly (P