Influence of endocytosis-stimulating hormones on the protein binding capacity of the cell membrane.

Histamine and serotonin enhanced the adsorption of fluorescein isothiocyanate (FITC)-labelled bovine serum albumin (BSA) to the membrane of Tetrahymena in a statistically significant and biologically relevant degree, while the similar action of insulin and epinephrine was not significant in either respect. The degree of hormonal influence on BSA-binding was similar to that exerted by the same hormones on the phagocytosis of protozoa in earlier studies. This supports the hypothetical implication that enhancement of protein adsorption to the cell membrane is an important element in the endocytosis stimulating action of histamine and serotonin.