The rat pituitary cell line, GH3, and its subclones secret significant amounts of prolactin (PRL). The GH3/B6 cells are generally grown in Ham's F12 medium supplemented with 15% horse serum and 2.5% fetal calf serum. In routine conditions, the doubling time of GH3/B6 cells varies from 30 to 52hr, depending on the qualities of the serum. The GH3/B6 cells are used to study the effects of several hormones on prolactin secretion. The recent works have shown that pectic acid increases secretion of prolactin. Pectic acid releases stored prolactin in cells and after a short time it appears to be effective. After being incubated with pectic acid for 30 minutes the cells started to become circular, protuberant shape and entered the secreting phase. pectic acid had not significant effect in number of cells but a decrease in total amount of protein was observed. After pectic acid was added, a significant decrease happened in the medium pH and this decrease caused unfavorable condition for cells. To solve this problem, the medium with Hepes was used. Hepes had been used extensively in cell culture due to its excellent buffering capacity in the physiological range. After a while; however, the cells appearance changed, their growth decreased, cytoplasmics vacuoles and membrane inclusion bodies developed and the viability decreased. Hepes stimulates the production of toxic oxygen metabolites such as hydrogen peroxide which itself results in a decrease in growth of GH3/B6 cells. Consequently, Hepes was replaced by NaOH in this experiment. NaOH had no effect on the cells and the pH was adjusted in 7.2.