Sea cucumbers are an abundant group of motile reef invertebrates. They have a special organ called Cuvierian organ that contains toxic substances. The present study aims to show the effect of the sublethal dose of the extract of sea cucumber Holathuria arta on liver and kidney functions in rats at different intervals (half hour, one hour, 6 hours, 12 hours and 24 hours). Specimens of sea cucumbers were collected from the Red sea, Egypt.  
The sublethal dose (LD₂₅) of the extract of sea cucumber Holothuria atra showed that GOT/AST was not significantly affected although serum GPT/ALT (normal serum level 70.8±3.25 g/ L) was significantly increased  reaching maximum value after 6 hours of injection (90.3%) then decreased throughout the experiment. Serum albumin wasn't significantly affected  after injection with (LD₂₅). Also, the total protein didn't show significant change.
The kidney function of the rat was measured by urea and creatinine after injection of (LD₂₅) of the extract of sea cucumber Holothuria atra. Urealevel showeda sharp significant increase and reaching its maximum value after 6 hours of injection (122%), then decreased throughout the experimental period and became non  significantly effective after 12 hours. On the other hand, creatinine also showed a significant increase reaching maximum value after 6 hours of injection (112.5%) then decreased through the experiment as urea but it reached normal level after 24 hours.
In conclusion, the extract toxin of sea cucumber of Holothuria atra has direct effect on ALT with no other effect on liver function test parameters, while it has sharp effect on kidney function test parameters.