Effect of phorbol 12-myristate 13-acetate (PMA) on the phosphoinositol (PI) system in Tetrahymena. Study of the 32P incorporation and breakdown of phospholipids.

Phorbol 12-myristate 13-acetate (PMA) treatment elicited an increased 32P incorporation into phospholipids namely phosphatidyl-inositol (PI); phosphatidyl-inositol-4-phosphate (PIP); phosphatidyl-inositol-4,5-bis-phosphate (PIP2); phosphatidyl-acid (PA); phosphatidyl-choline (PC) and phosphatidyl-ethanolamine (PE) particularly at the 20-30th min after treatment. The ratio of members of the phosphoinositol system, especially PIP and PI, related to the total phospholipid content was increased. PMA (2 x 10(-7) M) was the most effective of the three concentrations tested. The results call attention to the presence of a working phosphoinositol system in Protozoa.