Prostaglandin F1alpha (PGF1alpha) is the putative metabolite of dihomo-gamma-linolenic acid (DGLA) via the cyclooxygenase (COX) pathway. Both PGF1alpha and PGF2alpha have been shown to act as priming pheromones for male Atlantic salmon with a threshold concentration of 10-11 M. (1) PGF1alpha binds to the ovine corpus luteum FP receptor at only 8% of the relative potency of PGF2alpha. (2) It is only half as active as PGF2alpha in inducing human respiratory smooth muscle contractions in vitro. (3)