Tubular epithelial cells of nephron can absorb nitrogenous wastes by

Tubular epithelial cells of nephron absorb nitrogenous wastes by passive transport. 

Nitrogenous wastes are the components which contain nitrogen. These include urea and ammonia formed from the deamination of amino acids, creatinine formed from the breakdown of creatine phosphate, uric acid formed from the catabolism of nucleic acids, and urobilin formed from the breakdown of hemoglobin.