Protein factors regulating mammalian cell growth

Area of Science:

• Cell biology
• Biochemistry
• Endocrinology

Background:

• Pituitary factor (PF) is a protein preparation from pituitary glands.
• Cell growth stimulation is a key biological process with implications in development and disease.

Purpose of the Study:

• To characterize the nature of pituitary factor (PF) and its growth-promoting activity.
• To investigate whether PF's activity is mediated by proteases.
• To explore the potential secretion of growth factors by pituitary cell lines.

Main Methods:

• Assaying PF's effect on the growth of 3T3 mouse fibroblasts, WI-38 human fibroblasts, Y-1 mouse adrenal cells, and C-6 rat glial cells.
• Testing the activity of proteases (trypsin, thrombin) under PF assay conditions.
• Treating PF with PMSF (phenilmethyl sulfonyl fluoride) to assess its effect on activity.
• Measuring protease activity in PF using substrates like BAPNA, azocasein, and azoalbumin.
• Culturing a rat pituitary cell line (GH3) to assess potential growth factor secretion.

Main Results:

• PF demonstrated growth-stimulating activity across multiple cell types.
• Proteases like trypsin and thrombin did not exhibit growth-promoting activity in the PF assay.
• PMSF treatment did not inactivate PF's growth-promoting effect.
• No significant protease activity was detected in PF preparations.
• Preliminary data suggests the GH3 rat pituitary cell line may secrete a growth factor.

Conclusions:

• The growth-promoting activity of PF is likely not due to protease contamination.
• PF represents a non-proteolytic growth factor from the pituitary.
• Pituitary cell lines, such as GH3, are potential sources of novel growth factors.