The Effect of Antihistamines on the Pigments of Green Protista.

SUMMARY. A preliminary survey of the influence of a number of antihistamines on growth of several protozoa indicated that not only growth but also pigment formation in green forms was inhibited. Subsequently, it was demonstrated that molar concentrations of the drugs of less than 1 times 10⁻³ caused chlorosis of cultures of Euglena gracilis var. bacillaris, Chlamydomonas pseudococcum , and Chlorella vulgaris.
With the aid of one of the antihistamines, Pyribenzamine (CIBA), a permanently colorless culture of Euglena was obtained. This culture has been maintained in the chlorotic state in antihistamine-free medium through eighteen serial transfers in constant light. Comparative spectro-photometric studies were made of the pigments extracted from this new euglenid strain with those from normal green, dark-grown and streptomycin-bleached euglenas. Although the dark-etiolated forms retained small amounts of chlorophylls, neither of the drug-bleached cultures showed evidence of these pigments. Quantitatively, the carotenoid picture in dark-bleached and streptomycin-grown organisms was similar, but these pigments were greatly reduced in the Pyribenzamine-treated strain. Further studies on the identity of the carotenoids in the new euglenid are in progress.