Progesterone-BSA is a conjugate of progesterone and bovine serum albumin (BSA). Due to its large molecular weight, this product is cell-membrane impermeable and binds to proteins such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH) to modulate their enzymatic activity. It is used to differentiate non-genomic effects mediated by membrane receptors from genomic effects mediated by intracellular receptors, serving as a pharmacological tool for researching the membrane-associated mechanisms of steroid hormones.