A Role for Fenugreek in Altering the Osmoregulatory Capacity in Rainbow Trout (Oncorhynchus Mykiss)

Fenugreek (Trigonella foenum-graecum) is a botanical galactogogue that has been shown to increase milk production and serum prolactin in mammals. Prolactin is classically considered to be a freshwater-adapting hormone in teleost fishes. If fenugreek promotes prolactin synthesis, then it has the potential to decrease perturbations associated with exposure to hypoosmotic conditions in fishes. To test this, rainbow trout (Onchorhynchus mykiss) were fed doses of fenugreek, and endpoints of ionoregulatory ability were assessed. A single dose was used in a hypoosmotic stress experiment. Fenugreek did not disrupt systemic endpoints of salt-and-water balance. Transcript abundance of prolactin receptor in the gill and hypothalamus, and corticosteroid receptors in the gill decreased. Fenugreek resulted in an increase in claudin-7 and -30, and a decrease in claudin-33b. While it was demonstrated that fenugreek can impact salt-water balance, and affect changes similar to freshwater acclimation, it is unlikely that these changes were brought about via prolactin.