Poloxamer 338 (F108)

A subchronic/chronic oral toxicity study detects systemic adverse effects caused by repeated administration of a test article, using mortality, clinical signs, body weight, food/water intake, ophthalmology, urinalysis, hematology, serum biochemistry, organ weights, gross necropsy, and histopathology as integrated readouts. The readout reflects dose-related physiological injury, target-organ pathology, reversibility after recovery, and derivation of NOAEL, LOAEL, or related point-of-departure values when the dataset supports them.

A repeated-dose oral toxicity study evaluates systemic toxic effects after daily oral exposure to a test substance for a defined period, commonly 28 days, 6 weeks, 90 days, or 13 weeks in rodent studies. The readout is generated by integrating mortality, clinical signs, body-weight change, food and water intake, functional or behavioral observations, hematology, serum biochemistry, urinalysis, organ weights, necropsy, and histopathology to identify dose-related adverse effects, target organs, and the no-observed-adverse-effect level (NOAEL).

The following protocol uses the MTT colorimetric assay as a classic literature-established method for assessing cell viability/metabolic activity in cultured mammalian cells. MTT[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] is reduced by metabolically active cells to a colored formazan product; the amount of formazan is quantified spectrophotometrically and provides an indirect measure of metabolically active viable cells. Importantly, MTT reduction reflects cellular oxidoreductase/metabolic activity rather than an absolute direct count of living cells, so changes in cellular metabolism can alter the signal independently of cell number.