What substances is found in plasma but is not usually in the tubular fluid?

In plasma, substances like proteins (e.g., albumin) are present, but they are typically not found in tubular fluid because they are too large to pass through the glomerular filtration barrier in the kidneys. Additionally, certain hormones and large molecules are also retained in the plasma and not usually found in the tubular fluid. This selective filtration helps maintain the proper composition of blood and prevents the loss of essential proteins.